General Parameters (GNU Compiler Collection (GCC) Internals)

### 30.1 General Parameters ¶

The following choices of name are recognized for all targets:

`auto-profile-bbs` ¶

  If non-zero and used together with `-fauto-profile`, the auto-profile is used to determine basic block profile. If zero, then only function level profile is read.

`auto-profile-reorder-only` ¶

  Enable only function reordering with auto-profile.

`phiopt-factor-max-stmts-live` ¶

  When factoring statements out of if/then/else, this is the maximum number of statements after the defining statement to be allowed to extend the lifetime of a name.

`predictable-branch-outcome` ¶

  When branch is predicted to be taken with probability lower than this threshold (as a percentage), then it is considered well-predictable.

`max-rtl-if-conversion-insns` ¶

  RTL if-conversion tries to remove conditional branches around a block and replace them with conditionally executed instructions. This parameter gives the maximum number of instructions in a block that should be considered for if-conversion. The compiler also uses other heuristics to decide whether if-conversion is likely to be profitable.

`file-cache-files` ¶

  The maximum number of files in the file cache. The file cache is used to print source lines in diagnostics and do some source checks like `-Wmisleading-indentation`.

`file-cache-lines` ¶

  Maximum number of lines to index into file cache. When zero this is automatically sized. The file cache is used to print source lines in diagnostics and do some source checks like `-Wmisleading-indentation`.

`max-rtl-if-conversion-predictable-cost` ¶

  RTL if-conversion tries to remove conditional branches around a block and replace them with conditionally executed instructions. These parameters give the maximum permissible cost for the sequence that would be generated by if-conversion depending on whether the branch is statically determined to be predictable or not. The units for this parameter are the same as those for the GCC internal seq_cost metric. The compiler tries to provide a reasonable default for this parameter using the `BRANCH_COST` target macro.

`max-crossjump-edges` ¶

  The maximum number of incoming edges to consider for cross-jumping. The algorithm used by `-fcrossjumping` is O(N^2) in the number of edges incoming to each block. Increasing values mean more aggressive optimization, making the compilation time increase with probably small improvement in executable size.

`min-crossjump-insns` ¶

  The minimum number of instructions that must be matched at the end of two blocks before cross-jumping is performed on them. This value is ignored in the case where all instructions in the block being cross-jumped from are matched.

`max-grow-copy-bb-insns` ¶

  The maximum code size expansion factor when copying basic blocks instead of jumping. The expansion is relative to a jump instruction.

`max-goto-duplication-insns` ¶

  The maximum number of instructions to duplicate to a block that jumps to a computed goto. To avoid O(N^2) behavior in a number of passes, GCC factors computed gotos early in the compilation process, and unfactors them as late as possible. Only computed jumps at the end of a basic blocks with no more than `max-goto-duplication-insns` are unfactored.

`max-delay-slot-insn-search` ¶

  The maximum number of instructions to consider when looking for an instruction to fill a delay slot. If more than this arbitrary number of instructions are searched, the time savings from filling the delay slot are minimal, so stop searching. Increasing values mean more aggressive optimization, making the compilation time increase with probably small improvement in execution time.

`max-delay-slot-live-search` ¶

  When trying to fill delay slots, the maximum number of instructions to consider when searching for a block with valid live register information. Increasing this arbitrarily-chosen value means more aggressive optimization, increasing the compilation time. This parameter should be removed when the delay slot code is rewritten to maintain the control-flow graph.

`max-devirt-targets` ¶

  This limits number of function a virtual call may be speculatively devirtualized to using static analysis (without profile feedback).

`max-gcse-memory` ¶

  The approximate maximum amount of memory in `kB` that can be allocated in order to perform the global common subexpression elimination optimization. If more memory than specified is required, the optimization is not done.

`max-gcse-insertion-ratio` ¶

  If the ratio of expression insertions to deletions is larger than this value for any expression, then RTL PRE inserts or removes the expression and thus leaves partially redundant computations in the instruction stream.

`max-pending-list-length` ¶

  The maximum number of pending dependencies scheduling allows before flushing the current state and starting over. Large functions with few branches or calls can create excessively large lists which needlessly consume memory and resources.

`max-modulo-backtrack-attempts` ¶

  The maximum number of backtrack attempts the scheduler should make when modulo scheduling a loop. Larger values can exponentially increase compilation time.

`max-inline-functions-called-once-loop-depth` ¶

  Maximal loop depth of a call considered by inline heuristics that tries to inline all functions called once.

`max-inline-functions-called-once-insns` ¶

  Maximal estimated size of functions produced while inlining functions called once.

`max-inline-insns-single` ¶

  Several parameters control the tree inliner used in GCC. This number sets the maximum number of instructions (counted in GCC’s internal representation) in a single function that the tree inliner considers for inlining. This only affects functions declared inline and methods implemented in a class declaration (C++).

`max-inline-insns-auto` ¶

  When you use `-finline-functions` (included in `-O3`), a lot of functions that would otherwise not be considered for inlining by the compiler are investigated. To those functions, a different (more restrictive) limit compared to functions declared inline can be applied (`--param max-inline-insns-auto`).

`max-inline-insns-small` ¶

  This is the bound applied to calls that are considered relevant with `-finline-small-functions`.

`max-inline-insns-size` ¶

  This is the bound applied to calls that are optimized for size. Small growth may be desirable to anticipate optimization opportunities exposed by inlining.

`uninlined-function-insns` ¶

  Number of instructions accounted by inliner for function overhead such as function prologue and epilogue.

`uninlined-function-time` ¶

  Extra time accounted by inliner for function overhead such as time needed to execute function prologue and epilogue.

`inline-heuristics-hint-percent` ¶

  The scale (as a percentage) applied to `inline-insns-single`, `inline-insns-single-O2`, `inline-insns-auto` when inline heuristics hint that inlining is very profitable. It enables later optimizations.

`uninlined-thunk-insns` ¶
`uninlined-thunk-time`

  Same as `--param uninlined-function-insns` and `--param uninlined-function-time`, but applied to function thunks.

`inline-min-speedup` ¶

  When estimated performance improvement of caller + callee runtime exceeds this threshold (as a percentage), the function can be inlined regardless of the limit on `--param max-inline-insns-single` and `--param max-inline-insns-auto`.

`large-function-insns` ¶

  The limit specifying really large functions. For functions larger than this limit after inlining, inlining is constrained by `--param large-function-growth`. This parameter is useful primarily to avoid extreme compilation time caused by non-linear algorithms used by the back end.

`large-function-growth` ¶

  Specifies maximal growth of large functions caused by inlining, as a percentage. For example, a parameter value of 100 limits large function growth to 2.0 times the original size.

`large-unit-insns` ¶

  The limit specifying large translation unit. Growth caused by inlining of units larger than this limit is limited by `--param inline-unit-growth`. For small units this might be too tight. For example, consider a unit consisting of function A that is inline and B that just calls A three times. If B is small relative to A, the growth of unit is 300\% and yet such inlining is very sane. For very large units consisting of small inlineable functions, however, the overall unit growth limit is needed to avoid exponential explosion of code size. Thus for smaller units, the size is increased to `--param large-unit-insns` before applying `--param inline-unit-growth`.

`lazy-modules` ¶

  Maximum number of concurrently open C++ module files when lazy loading.

`inline-unit-growth` ¶

  Specifies maximal overall growth of the compilation unit caused by inlining. For example, parameter value 20 limits unit growth to 1.2 times the original size. Cold functions (either marked cold via an attribute or by profile feedback) are not accounted into the unit size.

`ipa-cp-unit-growth` ¶

  Specifies maximal overall growth of the compilation unit caused by interprocedural constant propagation. For example, parameter value 10 limits unit growth to 1.1 times the original size.

`ipa-cp-large-unit-insns` ¶

  The size of translation unit that IPA-CP pass considers large.

`large-stack-frame` ¶

  The limit specifying large stack frames. While inlining, the algorithm tries to not grow past this limit too much.

`large-stack-frame-growth` ¶

  Specifies maximal growth of large stack frames caused by inlining, as a percentage of the original size. For example, parameter value 1000 limits large stack frame growth to 11 times the original size.

`max-inline-insns-recursive` ¶
`max-inline-insns-recursive-auto`

  Specifies the maximum number of instructions an out-of-line copy of a self-recursive inline function can grow into by performing recursive inlining.

  `--param max-inline-insns-recursive` applies to functions declared inline. For functions not declared inline, recursive inlining happens only when `-finline-functions` (included in `-O3`) is enabled; `--param max-inline-insns-recursive-auto` applies instead.

`max-inline-recursive-depth` ¶
`max-inline-recursive-depth-auto`

  Specifies the maximum recursion depth used for recursive inlining.

  `--param max-inline-recursive-depth` applies to functions declared inline. For functions not declared inline, recursive inlining happens only when `-finline-functions` (included in `-O3`) is enabled; `--param max-inline-recursive-depth-auto` applies instead.

`min-inline-recursive-probability` ¶

  Recursive inlining is profitable only for functions having deep recursion in average and can hurt for functions having little recursion depth by increasing the prologue size or complexity of function body to other optimizers.

  When profile feedback is available (see `-fprofile-generate`), the actual recursion depth can be guessed from the probability that function recurses via a given call expression. This parameter limits inlining only to call expressions whose probability exceeds the given threshold (as a percentage).

`early-inlining-insns` ¶

  Specify growth that the early inliner can make. In effect it increases the amount of inlining for code having a large abstraction penalty.

`max-early-inliner-iterations` ¶

  Limit of iterations of the early inliner. This basically bounds the number of nested indirect calls the early inliner can resolve. Deeper chains are still handled by late inlining.

`comdat-sharing-probability` ¶

  Probability (as a percentage) that C++ inline function with comdat visibility are shared across multiple compilation units.

`modref-max-bases` ¶
`modref-max-refs` ¶
`modref-max-accesses`

  Specifies the maximal number of base pointers, references and accesses stored for a single function by mod/ref analysis.

`modref-max-tests` ¶

  Specifies the maxmal number of tests alias oracle can perform to disambiguate memory locations using the mod/ref information. This parameter ought to be bigger than `--param modref-max-bases` and `--param modref-max-refs`.

`modref-max-depth` ¶

  Specifies the maximum depth of DFS walk used by modref escape analysis. Setting to 0 disables the analysis completely.

`modref-max-escape-points` ¶

  Specifies the maximum number of escape points tracked by modref per SSA-name.

`modref-max-adjustments` ¶

  Specifies the maximum number times the access range is enlarged during modref dataflow analysis.

`profile-func-internal-id` ¶

  A parameter to control whether to use function internal id in profile database lookup. If the value is 0, the compiler uses an id that is based on function assembler name and filename, which makes old profile data more tolerant to source changes such as function reordering etc.

`min-vect-loop-bound` ¶

  The minimum number of iterations under which loops are not vectorized when `-ftree-vectorize` is used. The number of iterations after vectorization needs to be greater than the value specified by this option to allow vectorization.

`gcse-cost-distance-ratio` ¶

  Scaling factor in calculation of maximum distance an expression can be moved by GCSE optimizations. This is currently supported only in the code hoisting pass. The bigger the ratio, the more aggressive code hoisting is with simple expressions, i.e., the expressions that have cost less than `gcse-unrestricted-cost`. Specifying 0 disables hoisting of simple expressions.

`gcse-unrestricted-cost` ¶

  Cost, roughly measured as the cost of a single typical machine instruction, at which GCSE optimizations do not constrain the distance an expression can travel. This is currently supported only in the code hoisting pass. The lesser the cost, the more aggressive code hoisting is. Specifying 0 allows all expressions to travel unrestricted distances.

`max-hoist-depth` ¶

  The depth of search in the dominator tree for expressions to hoist. This is used to avoid quadratic behavior in hoisting algorithm. The value of 0 does not limit on the search, but may slow down compilation of huge functions.

`max-tail-merge-comparisons` ¶

  The maximum number of similar bbs to compare a bb with. This is used to avoid quadratic behavior in tree tail merging.

`max-tail-merge-iterations` ¶

  The maximum number of iterations of the tree tail merging pass over a function. This is used to limit compilation time in this pass.

`store-merging-allow-unaligned` ¶

  Allow the store merging pass to introduce unaligned stores if it is legal to do so.

`max-stores-to-merge` ¶

  The maximum number of stores to attempt to merge into wider stores in the store merging pass.

`max-store-chains-to-track` ¶

  The maximum number of store chains to track at the same time in the attempt to merge them into wider stores in the store merging pass.

`max-stores-to-track` ¶

  The maximum number of stores to track at the same time in the attempt to to merge them into wider stores in the store merging pass.

`max-unrolled-insns` ¶

  The maximum number of instructions that a loop may have to be unrolled. If a loop is unrolled, this parameter also determines how many times the loop code is unrolled.

`max-average-unrolled-insns` ¶

  The maximum number of instructions biased by probabilities of their execution that a loop may have to be unrolled. If a loop is unrolled, this parameter also determines how many times the loop code is unrolled.

`max-unroll-times` ¶

  The maximum number of unrollings of a single loop.

`max-peeled-insns` ¶

  The maximum number of instructions that a loop may have to be peeled. If a loop is peeled, this parameter also determines how many times the loop code is peeled.

`max-peel-times` ¶

  The maximum number of peelings of a single loop.

`max-peel-branches` ¶

  The maximum number of branches on the hot path through the peeled sequence.

`max-completely-peeled-insns` ¶

  The maximum number of insns of a completely peeled loop.

`max-completely-peel-times` ¶

  The maximum number of iterations of a loop to be suitable for complete peeling.

`max-completely-peel-loop-nest-depth` ¶

  The maximum depth of a loop nest suitable for complete peeling.

`max-unswitch-insns` ¶

  The maximum number of insns of an unswitched loop.

`max-unswitch-depth` ¶

  The maximum depth of a loop nest to be unswitched.

`lim-expensive` ¶

  The minimum cost of an expensive expression in the loop invariant motion pass.

`min-loop-cond-split-prob` ¶

  When FDO profile information is available, `min-loop-cond-split-prob` specifies the minimum threshold for probability of semi-invariant condition statement to trigger loop split. The value is a percentage.

`iv-consider-all-candidates-bound` ¶

  Bound on number of candidates for induction variables, below which all candidates are considered for each use in induction variable optimizations. If there are more candidates than this, only the most relevant ones are considered to avoid quadratic time complexity.

`iv-max-considered-uses` ¶

  The induction variable optimizations give up on loops that contain more induction variable uses than this limit.

`iv-always-prune-cand-set-bound` ¶

  This parameter is used by induction variable optimization. If the number of candidates in the iv set is larger than this value, always try to remove unnecessary ivs from the set when adding a new one.

`avg-loop-niter` ¶

  Average number of iterations of a loop.

`dse-max-object-size` ¶

  Maximum size (in bytes) of objects tracked bytewise by dead store elimination. Larger values may result in larger compilation times.

`dse-max-alias-queries-per-store` ¶

  Maximum number of queries into the alias oracle per store. Larger values result in larger compilation times and may result in more removed dead stores.

`scev-max-expr-size` ¶

  Bound on size of expressions used in the scalar evolutions analyzer. Large expressions slow the analyzer.

`scev-max-expr-complexity` ¶

  Bound on the complexity of the expressions in the scalar evolutions analyzer. Complex expressions slow the analyzer.

`max-tree-if-conversion-phi-args` ¶

  Maximum number of arguments in a PHI supported by TREE if conversion unless the loop is marked with a simd pragma.

`vect-max-layout-candidates` ¶

  The maximum number of possible vector layouts (such as permutations) to consider when optimizing to-be-vectorized code.

`vect-max-version-for-alignment-checks` ¶

  The maximum number of run-time checks that can be performed when doing loop versioning for alignment in the vectorizer.

`vect-max-version-for-alias-checks` ¶

  The maximum number of run-time checks that can be performed when doing loop versioning for alias in the vectorizer.

`vect-max-peeling-for-alignment` ¶

  The maximum number of loop peels to enhance access alignment for vectorizer. Value -1 means no limit.

`max-iterations-to-track` ¶

  The maximum number of iterations of a loop the brute-force algorithm for analysis of the number of iterations of the loop tries to evaluate.

`hot-bb-count-fraction` ¶

  The denominator n of fraction 1/n of the maximal execution count of a basic block in the entire program that a basic block needs to at least have in order to be considered hot. The default is 10000, which means that a basic block is considered hot if its execution count is greater than 1/10000 of the maximal execution count. 0 means that it is never considered hot. Used in non-LTO mode.

`hot-bb-count-ws-permille` ¶

  The number of most executed permilles, ranging from 0 to 1000, of the profiled execution of the entire program to which the execution count of a basic block must be part of in order to be considered hot. The default is 990, which means that a basic block is considered hot if its execution count contributes to the upper 990 permilles, or 99.0%, of the profiled execution of the entire program. 0 means that it is never considered hot. Used in LTO mode.

`hot-bb-frequency-fraction` ¶

  The denominator n of fraction 1/n of the execution frequency of the entry block of a function that a basic block of this function needs to at least have in order to be considered hot. The default is 1000, which means that a basic block is considered hot in a function if it is executed more frequently than 1/1000 of the frequency of the entry block of the function. 0 means that it is never considered hot.

`unlikely-bb-count-fraction` ¶

  The denominator n of fraction 1/n of the number of profiled runs of the entire program below which the execution count of a basic block must be in order for the basic block to be considered unlikely executed. The default is 20, which means that a basic block is considered unlikely executed if it is executed in fewer than 1/20, or 5%, of the runs of the program. 0 means that it is always considered unlikely executed.

`max-predicted-iterations` ¶

  The maximum number of loop iterations we predict statically. This is useful in cases where a function contains a single loop with known bound and another loop with unknown bound. The known number of iterations is predicted correctly, while the unknown number of iterations average to roughly 10. This means that the loop without bounds appears artificially cold relative to the other one.

`builtin-expect-probability` ¶

  Control the probability of the expression having the specified value, as a percentage.

`builtin-string-cmp-inline-length` ¶

  The maximum length of a constant string for a builtin `strcmp` or `memcmp` call to be eligible for inlining.

`align-threshold` ¶

  Select fraction of the maximal frequency of executions of a basic block in a function to align the basic block.

`align-loop-iterations` ¶

  A loop expected to iterate at least the selected number of iterations is aligned.

`tracer-dynamic-coverage` ¶
`tracer-dynamic-coverage-feedback`

  This value is used to limit superblock formation once the given percentage of executed instructions is covered. This limits unnecessary code size expansion.

  The `tracer-dynamic-coverage-feedback` parameter is used only when profile feedback is available. The real profiles (as opposed to statically estimated ones) are much less balanced allowing the threshold to be a larger value.

`tracer-max-code-growth` ¶

  Stop tail duplication once code growth has reached given percentage. This is a rather artificial limit, as most of the duplicates are eliminated later in cross jumping, so it may be set to much higher values than is the desired code growth.

`tracer-min-branch-ratio` ¶

  Stop reverse growth when the reverse probability of best edge is less than this threshold (as a percentage).

`tracer-min-branch-probability` ¶
`tracer-min-branch-probability-feedback`

  Stop forward growth if the best edge has probability lower than this threshold.

  Similarly to `tracer-dynamic-coverage` two parameters are provided. `tracer-min-branch-probability-feedback` is used for compilation with profile feedback and `tracer-min-branch-probability` compilation without. The value for compilation with profile feedback needs to be more conservative (higher) in order to make tracer effective.

`stack-clash-protection-guard-size` ¶

  Specify the size of the operating system provided stack guard as 2 raised to num bytes. Higher values may reduce the number of explicit probes, but a value larger than the guard provided by the operating system leaves code vulnerable to stack clash style attacks.

`stack-clash-protection-probe-interval` ¶

  Stack clash protection involves probing stack space as it is allocated. This parameter controls the maximum distance between probes into the stack as 2 raised to num bytes. Higher values may reduce the number of explicit probes, but a value larger than the guard provided by the operating system leaves code vulnerable to stack clash style attacks.

`max-cse-path-length` ¶

  The maximum number of basic blocks on path that CSE considers.

`max-cse-insns` ¶

  The maximum number of instructions CSE processes before flushing.

`ggc-min-expand` ¶

  GCC uses a garbage collector to manage its own memory allocation. This parameter specifies the minimum percentage by which the garbage collector’s heap should be allowed to expand between collections. Tuning this may improve compilation speed; it has no effect on code generation.

  The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when RAM >= 1GB. If `getrlimit` is available, the notion of “RAM” is the smallest of actual RAM and `RLIMIT_DATA` or `RLIMIT_AS`. If GCC is not able to calculate RAM on a particular platform, the lower bound of 30% is used. Setting this parameter and `ggc-min-heapsize` to zero causes a full collection to occur at every opportunity. This is extremely slow, but can be useful for debugging.

`ggc-min-heapsize` ¶

  Minimum size of the garbage collector’s heap before it begins bothering to collect garbage. The first collection occurs after the heap expands by `ggc-min-expand`% beyond `ggc-min-heapsize`. Again, tuning this may improve compilation speed, and has no effect on code generation.

  The default is the smaller of RAM/8, `RLIMIT_RSS`, or a limit that tries to ensure that `RLIMIT_DATA` or `RLIMIT_AS` are not exceeded, but with a lower bound of 4096 (four megabytes) and an upper bound of 131072 (128 megabytes). If GCC is not able to calculate RAM on a particular platform, the lower bound is used. Setting this parameter very large effectively disables garbage collection. Setting this parameter and `ggc-min-expand` to zero causes a full collection to occur at every opportunity.

`max-reload-search-insns` ¶

  The maximum number of instruction reload should look backward for equivalent register. Increasing values mean more aggressive optimization, making the compilation time increase with probably slightly better performance.

`max-cselib-memory-locations` ¶

  The maximum number of memory locations cselib should take into account. Increasing values mean more aggressive optimization, making the compilation time increase with probably slightly better performance.

`max-sched-ready-insns` ¶

  The maximum number of instructions ready to be issued the scheduler should consider at any given time during the first scheduling pass. Increasing values mean more thorough searches, making the compilation time increase with probably little benefit.

`max-sched-region-blocks` ¶

  The maximum number of blocks in a region to be considered for interblock scheduling.

`max-pipeline-region-blocks` ¶

  The maximum number of blocks in a region to be considered for pipelining in the selective scheduler.

`max-sched-region-insns` ¶

  The maximum number of insns in a region to be considered for interblock scheduling.

`max-pipeline-region-insns` ¶

  The maximum number of insns in a region to be considered for pipelining in the selective scheduler.

`min-spec-prob` ¶

  The minimum probability (as a percentage) of reaching a source block for interblock speculative scheduling.

`max-sched-extend-regions-iters` ¶

  The maximum number of iterations through CFG to extend regions. A value of 0 disables region extensions.

`max-sched-insn-conflict-delay` ¶

  The maximum conflict delay for an insn to be considered for speculative motion.

`sched-spec-prob-cutoff` ¶

  The minimal probability of speculation success (as a percentage), so that speculative insns are scheduled.

`sched-state-edge-prob-cutoff` ¶

  The minimum probability an edge must have for the scheduler to save its state across it.

`sched-mem-true-dep-cost` ¶

  Minimal distance (in CPU cycles) between store and load targeting same memory locations.

`selsched-max-lookahead` ¶

  The maximum size of the lookahead window of selective scheduling. It is a depth of search for available instructions.

`selsched-max-sched-times` ¶

  The maximum number of times that an instruction is scheduled during selective scheduling. This is the limit on the number of iterations through which the instruction may be pipelined.

`selsched-insns-to-rename` ¶

  The maximum number of best instructions in the ready list that are considered for renaming in the selective scheduler.

`sms-min-sc` ¶

  The minimum value of stage count that swing modulo scheduler generates.

`max-last-value-rtl` ¶

  The maximum size, measured as number of RTLs, that can be recorded in an expression in the combiner for a pseudo-register as the last known value of that register.

`max-combine-insns` ¶

  The maximum number of instructions the RTL combiner tries to combine.

`max-combine-search-insns` ¶

  The maximum number of instructions that the RTL combiner searches in order to find the next use of a given register definition. If this limit is reached without finding such a use, the combiner stops trying to optimize the definition.

  Currently this limit only applies after certain successful combination attempts, but it could be extended to other cases in future.

`integer-share-limit` ¶

  Small integer constants can use a shared data structure, reducing the compiler’s memory usage and increasing its speed. This sets the maximum value of a shared integer constant.

`ssp-buffer-size` ¶

  The minimum size of buffers (i.e. arrays) that receive stack smashing protection when `-fstack-protector` is used.

`min-size-for-stack-sharing` ¶

  The minimum size of variables taking part in stack slot sharing when not optimizing.

`max-jump-thread-duplication-stmts` ¶

  Maximum number of statements allowed in a block that needs to be duplicated when threading jumps.

`max-jump-thread-paths` ¶

  The maximum number of paths to consider when searching for jump threading opportunities. When arriving at a block, incoming edges are only considered if the number of paths to be searched so far multiplied by the number of incoming edges does not exhaust the specified maximum number of paths to consider.

`max-fields-for-field-sensitive` ¶

  Maximum number of fields in a structure treated in a field-sensitive manner during pointer analysis.

`prefetch-latency` ¶

  Estimate on average number of instructions that are executed before prefetch finishes. The distance prefetched ahead is proportional to this constant. Increasing this number may also lead to less streams being prefetched (see `simultaneous-prefetches`).

`simultaneous-prefetches` ¶

  Maximum number of prefetches that can run at the same time.

`l1-cache-line-size` ¶

  The size of cache line in L1 data cache, in bytes.

`l1-cache-size` ¶

  The size of L1 data cache, in kilobytes.

`l2-cache-size` ¶

  The size of L2 data cache, in kilobytes.

`prefetch-dynamic-strides` ¶

  Whether the loop array prefetch pass should issue software prefetch hints for strides that are non-constant. In some cases this may be beneficial, though the fact the stride is non-constant may make it hard to predict when there is clear benefit to issuing these hints.

  Set to 1 if the prefetch hints should be issued for non-constant strides. Set to 0 if prefetch hints should be issued only for strides that are known to be constant and below `prefetch-minimum-stride`.

`prefetch-minimum-stride` ¶

  Minimum constant stride, in bytes, to start using prefetch hints for. If the stride is less than this threshold, prefetch hints are not issued.

  This setting is useful for processors that have hardware prefetchers, in which case there may be conflicts between the hardware prefetchers and the software prefetchers. If the hardware prefetchers have a maximum stride they can handle, it should be used here to improve the use of software prefetchers.

  A value of -1 means we don’t have a threshold and therefore prefetch hints can be issued for any constant stride.

  This setting is only useful for strides that are known and constant.

`destructive-interference-size` ¶
`constructive-interference-size`

  The values for the C++17 variables `std::hardware_destructive_interference_size` and `std::hardware_constructive_interference_size`. The destructive interference size is the minimum recommended offset between two independent concurrently-accessed objects; the constructive interference size is the maximum recommended size of contiguous memory accessed together. Typically both are the size of an L1 cache line for the target, in bytes. For a generic target covering a range of L1 cache line sizes, typically the constructive interference size is the small end of the range and the destructive size is the large end.

  The destructive interference size is intended to be used for layout, and thus has ABI impact. The default value is not expected to be stable, and on some targets varies with `-mtune`, so use of this variable in a context where ABI stability is important, such as the public interface of a library, is strongly discouraged; if it is used in that context, users can stabilize the value using this option.

  The constructive interference size is less sensitive, as it is typically only used in a ‘`static_assert`’ to make sure that a type fits within a cache line.

  See also `-Winterference-size`.

`loop-interchange-max-num-stmts` ¶

  The maximum number of stmts in a loop to be interchanged.

`loop-interchange-stride-ratio` ¶

  The minimum ratio between stride of two loops for interchange to be profitable.

`min-insn-to-prefetch-ratio` ¶

  The minimum ratio between the number of instructions and the number of prefetches to enable prefetching in a loop.

`prefetch-min-insn-to-mem-ratio` ¶

  The minimum ratio between the number of instructions and the number of memory references to enable prefetching in a loop.

`use-canonical-types` ¶

  Whether the compiler should use the “canonical” type system. Should always be 1, which uses a more efficient internal mechanism for comparing types in C++ and Objective-C++. However, if bugs in the canonical type system are causing compilation failures, set this value to 0 to disable canonical types.

`switch-conversion-max-branch-ratio` ¶

  Switch initialization conversion refuses to create arrays that are bigger than `switch-conversion-max-branch-ratio` times the number of branches in the switch.

`max-partial-antic-length` ¶

  Maximum length of the partial antic set computed during the tree partial redundancy elimination optimization (`-ftree-pre`) when optimizing at `-O3` and above. For some sorts of source code the enhanced partial redundancy elimination optimization can run away, consuming all of the memory available on the host machine. This parameter sets a limit on the length of the sets that are computed, which prevents the runaway behavior. Setting a value of 0 for this parameter allows an unlimited set length.

`rpo-vn-max-loop-depth` ¶

  Maximum loop depth that is value-numbered optimistically. When the limit hits the innermost rpo-vn-max-loop-depth loops and the outermost loop in the loop nest are value-numbered optimistically and the remaining ones not.

`sccvn-max-alias-queries-per-access` ¶

  Maximum number of alias-oracle queries we perform when looking for redundancies for loads and stores. If this limit is hit the search is aborted and the load or store is not considered redundant. The number of queries is algorithmically limited to the number of stores on all paths from the load to the function entry.

`ira-max-loops-num` ¶

  IRA uses regional register allocation by default. If a function contains more loops than the number given by this parameter, only at most the given number of the most frequently-executed loops form regions for regional register allocation.

`ira-max-conflict-table-size` ¶

  Although IRA uses a sophisticated algorithm to compress the conflict table, the table can still require excessive amounts of memory for huge functions. If the conflict table for a function could be more than the size in MB given by this parameter, the register allocator instead uses a faster, simpler, and lower-quality algorithm that does not require building a pseudo-register conflict table.

`ira-loop-reserved-regs` ¶

  IRA can be used to evaluate more accurate register pressure in loops for decisions to move loop invariants (see `-O3`). The number of available registers reserved for some other purposes is given by this parameter. The default value of the parameter is the best found from numerous experiments.

`ira-consider-dup-in-all-alts` ¶

  Make IRA to consider matching constraint (duplicated operand number) heavily in all available alternatives for preferred register class. If it is set as zero, it means IRA only respects the matching constraint when it’s in the only available alternative with an appropriate register class. Otherwise, it means IRA checks all available alternatives for preferred register class even if it has found some choice with an appropriate register class that satisfies the found qualified matching constraint.

`ira-simple-lra-insn-threshold` ¶

  Approximate function insn number in 1K units triggering simple local RA.

`lra-inheritance-ebb-probability-cutoff` ¶

  LRA tries to reuse values reloaded in registers in subsequent insns. This optimization is called inheritance. EBB is used as a region to do this optimization. The parameter defines a minimal fall-through edge probability (as a percentage) used to add BB to inheritance EBB in LRA. The default value was chosen from numerous runs of SPEC2000 on x86-64.

`loop-invariant-max-bbs-in-loop` ¶

  Loop invariant motion can be very expensive, both in compilation time and in amount of needed compile-time memory, with very large loops. Loops with more basic blocks than this parameter won’t have loop invariant motion optimization performed on them.

`loop-max-datarefs-for-datadeps` ¶

  Building data dependencies is expensive for very large loops. This parameter limits the number of data references in loops that are considered for data dependence analysis. These large loops are no handled by the optimizations using loop data dependencies.

`max-vartrack-size` ¶

  Sets a maximum number of hash table slots to use during variable tracking dataflow analysis of any function. If this limit is exceeded with variable tracking at assignments enabled, analysis for that function is retried without it, after removing all debug insns from the function. If the limit is exceeded even without debug insns, var tracking analysis is completely disabled for the function. Setting the parameter to zero makes it unlimited.

`max-vartrack-expr-depth` ¶

  Sets a maximum number of recursion levels when attempting to map variable names or debug temporaries to value expressions. This trades compilation time for more complete debug information. If this is set too low, value expressions that are available and could be represented in debug information may end up not being used; setting this higher may enable the compiler to find more complex debug expressions, but compile time and memory use may grow.

`max-debug-marker-count` ¶

  Sets a threshold on the number of debug markers (e.g. begin stmt markers) to avoid complexity explosion at inlining or expanding to RTL. If a function has more such gimple stmts than the set limit, such stmts are dropped from the inlined copy of a function and from its RTL expansion.

`min-nondebug-insn-uid` ¶

  Use uids starting at this parameter for nondebug insns. The range below the parameter is reserved exclusively for debug insns created by `-fvar-tracking-assignments`, but debug insns may get (non-overlapping) uids above it if the reserved range is exhausted.

`ipa-sra-deref-prob-threshold` ¶

  IPA-SRA replaces a pointer that is known not be NULL with one or more new parameters only when the probability (as a percentage, relative to function entry) of it being dereferenced is higher than this parameter.

`ipa-sra-ptr-growth-factor` ¶

  IPA-SRA replaces a pointer to an aggregate with one or more new parameters only when their cumulative size is less or equal to `ipa-sra-ptr-growth-factor` times the size of the original pointer parameter.

`ipa-sra-ptrwrap-growth-factor` ¶

  Additional maximum allowed growth of total size of new parameters that ipa-sra replaces a pointer to an aggregate with, if it points to a local variable that the caller only writes to and passes it as an argument to other functions.

`ipa-sra-max-replacements` ¶

  Maximum pieces of an aggregate that IPA-SRA tracks. As a consequence, it is also the maximum number of replacements of a formal parameter.

`sra-max-scalarization-size-Ospeed` ¶
`sra-max-scalarization-size-Osize`

  The two Scalar Reduction of Aggregates passes (SRA and IPA-SRA) aim to replace scalar parts of aggregates with uses of independent scalar variables. These parameters control the maximum size, in storage units, of aggregates that are considered for replacement when compiling for speed (`sra-max-scalarization-size-Ospeed`) or size (`sra-max-scalarization-size-Osize`) respectively.

`sra-max-propagations` ¶

  The maximum number of artificial accesses that Scalar Replacement of Aggregates (SRA) tracks, per one local variable, in order to facilitate copy propagation.

`tm-max-aggregate-size` ¶

  When making copies of thread-local variables in a transaction, this parameter specifies the size in bytes after which variables are saved with the logging functions as opposed to save/restore code sequence pairs. This option only applies when using `-fgnu-tm`.

`graphite-max-nb-scop-params` ¶

  To avoid exponential effects in the Graphite loop transforms, the number of parameters in a Static Control Part (SCoP) is bounded. A value of zero can be used to lift the bound. A variable whose value is unknown at compilation time and defined outside a SCoP is a parameter of the SCoP.

`hardcfr-max-blocks` ¶

  Disable `-fharden-control-flow-redundancy` for functions with a larger number of blocks than the specified value. Zero removes any limit.

`hardcfr-max-inline-blocks` ¶

  Force `-fharden-control-flow-redundancy` to use out-of-line checking for functions with a larger number of basic blocks than the specified value.

`loop-block-tile-size` ¶

  Loop blocking or strip mining transforms, enabled with `-floop-block` or `-floop-strip-mine`, strip mine each loop in the loop nest by a given number of iterations. The strip length can be changed using the `loop-block-tile-size` parameter.

`ipa-jump-function-lookups` ¶

  Specifies number of statements visited during jump function offset discovery.

`ipa-cp-value-list-size` ¶

  IPA-CP attempts to track all possible values and types passed to a function’s parameter in order to propagate them and perform devirtualization. `ipa-cp-value-list-size` is the maximum number of values and types it stores per one formal parameter of a function.

`ipa-cp-eval-threshold` ¶

  IPA-CP calculates its own score of cloning profitability heuristics and performs those cloning opportunities with scores that exceed `ipa-cp-eval-threshold`.

`ipa-cp-max-recursive-depth` ¶

  Maximum depth of recursive cloning for self-recursive function.

`ipa-cp-min-recursive-probability` ¶

  Recursive cloning only when the probability of call being executed exceeds the parameter.

`ipa-cp-recursive-freq-factor` ¶

  The number of times interprocedural copy propagation expects recursive functions to call themselves.

`ipa-cp-recursion-penalty` ¶

  Percentage penalty the recursive functions receive when they are evaluated for cloning.

`ipa-cp-single-call-penalty` ¶

  Percentage penalty functions containing a single call to another function receive when they are evaluated for cloning.

`ipa-cp-sweeps` ¶

  The number of times the interprocedural constant propagation traverses all functions to make cloning decisions.

`ipa-max-agg-items` ¶

  IPA-CP is also capable of propagating a number of scalar values passed in an aggregate. `ipa-max-agg-items` controls the maximum number of such values per one parameter.

`ipa-cp-loop-hint-bonus` ¶

  When IPA-CP determines that a cloning candidate would make the number of iterations of a loop known, it adds a bonus of `ipa-cp-loop-hint-bonus` to the profitability score of the candidate.

`ipa-max-loop-predicates` ¶

  The maximum number of different predicates IPA uses to describe when loops in a function have known properties.

`ipa-max-aa-steps` ¶

  During its analysis of function bodies, IPA-CP employs alias analysis in order to track values pointed to by function parameters. In order not spend too much time analyzing huge functions, it gives up and consider all memory clobbered after examining `ipa-max-aa-steps` statements modifying memory.

`ipa-max-switch-predicate-bounds` ¶

  Maximal number of boundary endpoints of case ranges of a switch statement. For switch exceeding this limit, IPA-CP does not construct a cloning cost predicate, which is used to estimate cloning benefit, for the default case of the switch statement.

`ipa-max-param-expr-ops` ¶

  IPA-CP analyzes conditional statements that reference some function parameter to estimate benefit for cloning upon certain constant value. But if number of operations in a parameter expression exceeds `ipa-max-param-expr-ops`, the expression is treated as complicated, and is not handled by IPA analysis.

`lto-partitions` ¶

  Specify desired number of partitions produced during WHOPR compilation. The number of partitions should exceed the number of CPUs used for compilation.

`lto-min-partition` ¶

  Minimum partition size for WHOPR (in estimated instructions). This prevents expenses of splitting very small programs into too many partitions.

`lto-max-partition` ¶

  Maximum partition size for WHOPR (in estimated instructions). to provide an upper bound for individual size of partition. Meant to be used only with balanced partitioning.

`lto-partition-locality-frequency-cutoff` ¶

  The denominator n of fraction 1/n of the execution frequency of the callee to be cloned for a particular caller. The special value of 0 dictates to always clone without a cut-off.

`lto-partition-locality-size-cutoff` ¶

  Size cut-off for callee including inlined calls to be cloned for a particular caller.

`lto-max-locality-partition` ¶

  Maximal size of a locality partition for LTO (in estimated instructions). Value of 0 results in default value being used.

`lto-max-streaming-parallelism` ¶

  Maximal number of parallel processes used for LTO streaming.

`cxx-max-namespaces-for-diagnostic-help` ¶

  The maximum number of namespaces to consult for suggestions when C++ name lookup fails for an identifier.

`sink-frequency-threshold` ¶

  The maximum relative execution frequency (as a percentage) of the target block relative to a statement’s original block to allow statement sinking of a statement. Larger numbers result in more aggressive statement sinking. A small positive adjustment is applied for statements with memory operands as those are even more profitable to sink.

`max-stores-to-sink` ¶

  The maximum number of conditional store pairs that can be sunk. Set to 0 if either vectorization (`-ftree-vectorize`) or if-conversion (`-ftree-loop-if-convert`) is disabled.

`case-values-threshold` ¶

  The smallest number of different values for which it is best to use a jump table instead of a tree of conditional branches. If the value is 0, use the default for the machine.

`jump-table-max-growth-ratio-for-size` ¶

  The maximum code size growth ratio when expanding into a jump table (as a percentage). The parameter is used when optimizing for size.

`jump-table-max-growth-ratio-for-speed` ¶

  The maximum code size growth ratio when expanding into a jump table (as a percentage). The parameter is used when optimizing for speed.

`tree-reassoc-width` ¶

  In the tree reassociation pass, set the maximum number of instructions executed in parallel in the reassociated tree. This parameter overrides target-dependent heuristics used by default if it has a nonzero value.

`sched-pressure-algorithm` ¶

  Choose between the two available implementations of `-fsched-pressure`. Algorithm 1 is the original implementation and is the more likely to prevent instructions from being reordered. Algorithm 2 was designed to be a compromise between the relatively conservative approach taken by algorithm 1 and the rather aggressive approach taken by the default scheduler. It relies more heavily on having a regular register file and accurate register pressure classes. See `haifa-sched.cc` in the GCC sources for more details.

  The default choice depends on the target.

`max-slsr-cand-scan` ¶

  Set the maximum number of existing candidates that are considered when seeking a basis for a new straight-line strength reduction candidate.

`asan-globals` ¶

  Enable buffer overflow detection for global objects. This kind of protection is enabled by default if you are using `-fsanitize=address` option. To disable global objects protection use `--param asan-globals=0`.

`asan-stack` ¶

  Enable buffer overflow detection for stack objects. This kind of protection is enabled by default when using `-fsanitize=address`. To disable stack protection use `--param asan-stack=0` option.

`asan-instrument-reads` ¶

  Enable buffer overflow detection for memory reads. This kind of protection is enabled by default when using `-fsanitize=address`. To disable memory reads protection use `--param asan-instrument-reads=0`.

`asan-instrument-writes` ¶

  Enable buffer overflow detection for memory writes. This kind of protection is enabled by default when using `-fsanitize=address`. To disable memory writes protection use `--param asan-instrument-writes=0` option.

`asan-memintrin` ¶

  Enable detection for built-in functions. This kind of protection is enabled by default when using `-fsanitize=address`. To disable built-in functions protection use `--param asan-memintrin=0`.

`asan-use-after-return` ¶

  Enable detection of use-after-return. This kind of protection is enabled by default when using the `-fsanitize=address` option. To disable it use `--param asan-use-after-return=0`.

  Note: By default the check is disabled at run time. To enable it, add `detect_stack_use_after_return=1` to the environment variable `ASAN_OPTIONS`.

`asan-instrumentation-with-call-threshold` ¶

  If number of memory accesses in function being instrumented is greater or equal to this number, use callbacks instead of inline checks. E.g. to disable inline code use `--param asan-instrumentation-with-call-threshold=0`.

`asan-kernel-mem-intrinsic-prefix` ¶

  If nonzero, prefix calls to `memcpy`, `memset` and `memmove` with ‘`__asan_`’ or ‘`__hwasan_`’ for `-fsanitize=kernel-address` or ‘`-fsanitize=kernel-hwaddress`’, respectively.

`hwasan-instrument-stack` ¶

  Enable hwasan instrumentation of statically-sized stack-allocated variables. This kind of instrumentation is enabled by default when using `-fsanitize=hwaddress` and disabled by default when using `-fsanitize=kernel-hwaddress`. To disable stack instrumentation use `--param hwasan-instrument-stack=0`, and to enable it use `--param hwasan-instrument-stack=1`.

`hwasan-random-frame-tag` ¶

  When using stack instrumentation, decide tags for stack variables using a deterministic sequence beginning at a random tag for each frame. With this parameter unset tags are chosen using the same sequence but beginning from 1. This is enabled by default for `-fsanitize=hwaddress` and unavailable for `-fsanitize=kernel-hwaddress` and `-fsanitize=memtag-stack`. To disable it use `--param hwasan-random-frame-tag=0`.

`hwasan-instrument-allocas` ¶

  Enable hwasan instrumentation of dynamically sized stack-allocated variables. This kind of instrumentation is enabled by default when using `-fsanitize=hwaddress` and disabled by default when using `-fsanitize=kernel-hwaddress`. To disable instrumentation of such variables use `--param hwasan-instrument-allocas=0`, and to enable it use `--param hwasan-instrument-allocas=1`.

`hwasan-instrument-reads` ¶

  Enable hwasan checks on memory reads. Instrumentation of reads is enabled by default for both `-fsanitize=hwaddress` and `-fsanitize=kernel-hwaddress`. To disable checking memory reads use `--param hwasan-instrument-reads=0`.

`hwasan-instrument-writes` ¶

  Enable hwasan checks on memory writes. Instrumentation of writes is enabled by default for both `-fsanitize=hwaddress` and `-fsanitize=kernel-hwaddress`. To disable checking memory writes use `--param hwasan-instrument-writes=0`.

`hwasan-instrument-mem-intrinsics` ¶

  Enable hwasan instrumentation of builtin functions. Instrumentation of these builtin functions is enabled by default for both `-fsanitize=hwaddress` and `-fsanitize=kernel-hwaddress`. To disable instrumentation of builtin functions use `--param hwasan-instrument-mem-intrinsics=0`.

`memtag-instrument-allocas` ¶

  Enable hardware-assisted memory tagging of dynamically sized stack-allocated variables. This kind of code generation is enabled by default when using `-fsanitize=memtag-stack`.

`memtag-instrument-mem-intrinsics` ¶

  When sanitizing using MTE instructions, include builtin functions.

`use-after-scope-direct-emission-threshold` ¶

  If the size of a local variable in bytes is smaller or equal to this number, directly poison (or unpoison) shadow memory instead of using run-time callbacks.

`tsan-distinguish-volatile` ¶

  Emit special instrumentation for accesses to volatiles.

`tsan-instrument-func-entry-exit` ¶

  Emit instrumentation calls to `__tsan_func_entry()` and `__tsan_func_exit()`.

`max-fsm-thread-path-insns` ¶

  Maximum number of instructions to copy when duplicating blocks on a finite state automaton jump thread path.

`threader-debug` ¶

  Enables verbose dumping of the threader solver. This parameter has two special values, ‘`none`’ and ‘`all`’.

`parloops-chunk-size` ¶

  Chunk size of OpenMP schedule for loops parallelized by parloops.

`parloops-schedule` ¶

  Schedule type of OpenMP schedule for loops parallelized by parloops (static, dynamic, guided, auto, runtime).

`parloops-min-per-thread` ¶

  The minimum number of iterations per thread of an innermost parallelized loop for which the parallelized variant is preferred over the single threaded one. Note that for a parallelized loop nest the minimum number of iterations of the outermost loop per thread is two.

`max-ssa-name-query-depth` ¶

  Maximum depth of recursion when querying properties of SSA names in things like fold routines. One level of recursion corresponds to following a use-def chain.

`max-speculative-devirt-maydefs` ¶

  The maximum number of may-defs we analyze when looking for a must-def specifying the dynamic type of an object that invokes a virtual call we may be able to devirtualize speculatively.

`ranger-debug` ¶

  Specifies the type of debug output to be issued for ranges.

`unroll-jam-min-percent` ¶

  The minimum percentage of memory references that must be optimized away for the unroll-and-jam transformation to be considered profitable.

`unroll-jam-max-unroll` ¶

  The maximum number of times the outer loop should be unrolled by the unroll-and-jam transformation.

`max-rtl-if-conversion-unpredictable-cost` ¶

  Maximum permissible cost for the sequence that would be generated by the RTL if-conversion pass for a branch that is considered unpredictable.

`max-variable-expansions-in-unroller` ¶

  If `-fvariable-expansion-in-unroller` is used, the maximum number of times that an individual variable is expanded during loop unrolling.

`partial-inlining-entry-probability` ¶

  Maximum probability of the entry BB of split region (as a percentage relative to entry BB of the function) to make partial inlining happen.

`max-tracked-strlens` ¶

  Maximum number of strings for which the strlen optimization pass tracks string lengths.

`gcse-after-reload-partial-fraction` ¶

  The threshold ratio for performing partial redundancy elimination after reload.

`gcse-after-reload-critical-fraction` ¶

  The threshold ratio of critical edges execution count that permit performing redundancy elimination after reload.

`max-loop-header-insns` ¶

  The maximum number of insns allowed in a loop header duplicated by the copy loop headers pass.

`vect-epilogues-nomask` ¶

  If nonzero, enable loop epilogue vectorization using smaller vector size.

`vect-partial-vector-usage` ¶

  Controls when the loop vectorizer considers using partial vector loads and stores as an alternative to falling back to scalar code. 0 stops the vectorizer from ever using partial vector loads and stores. 1 allows partial vector loads and stores if vectorization removes the need for the code to iterate. 2 allows partial vector loads and stores in all loops. The parameter only has an effect on targets that support partial vector loads and stores.

`vect-inner-loop-cost-factor` ¶

  The maximum factor that the loop vectorizer applies to the cost of statements in an inner loop relative to the loop being vectorized. The factor applied is the maximum of the estimated number of iterations of the inner loop and this parameter. The default value of this parameter is 50.

`vect-induction-float` ¶

  Enable loop vectorization of floating-point inductions.

`vect_allow_possibly_not_worthwhile_vectorizations` ¶

  Enable vectorization of loops that may not be profitable according to the cost model but still perform costing between vector modes.

`vrp-block-limit` ¶

  Maximum number of basic blocks before value range propagation switches to a simpler algorithm that uses less memory.

`vrp-cstload-limit` ¶

  Maximum number of steps when inferring a value range from a load from a constant aggregate.

`vrp-sparse-threshold` ¶

  Maximum number of basic blocks before value range propagation uses a sparse bitmap cache.

`vrp-switch-limit` ¶

  Maximum number of outgoing edges in a switch to allow it to be processed by value range propagation.

`vrp-vector-threshold` ¶

  Maximum number of basic blocks for value range propagation to use a basic cache vector.

`avoid-fma-max-bits` ¶

  Maximum number of bits for which we avoid creating FMAs.

`fully-pipelined-fma` ¶

  Whether the target fully pipelines FMA instructions. If non-zero, reassociation considers the benefit of parallelizing FMA’s multiplication part and addition part, assuming FMUL and FMA use the same units that can also do FADD.

`sms-loop-average-count-threshold` ¶

  A threshold on the average loop count considered by the swing modulo scheduler.

`sms-dfa-history` ¶

  The number of cycles the swing modulo scheduler considers when checking conflicts using DFA.

`graphite-allow-codegen-errors` ¶

  Whether codegen errors should be ICEs when `-fchecking`.

`sms-max-ii-factor` ¶

  A factor for tuning the upper bound that the swing modulo scheduler uses for scheduling a loop.

`lra-max-considered-reload-pseudos` ¶

  The maximum number of reload pseudos that are considered during spilling a non-reload pseudo.

`lra-max-pseudos-points-log2-considered-for-preferences` ¶

  The maximum `log2(number of reload pseudos * number of program points)` threshold when preferences for other reload pseudos are still considered. Taking these preferences into account helps to improve register allocation. However, for very large functions, a large value can result in significant compilation time and memory consumption. The default value is 30.

`max-pow-sqrt-depth` ¶

  Maximum depth of square root chains to use when synthesizing exponentiation by a real constant.

`max-dse-active-local-stores` ¶

  Maximum number of active local stores in RTL dead store elimination.

`asan-instrument-allocas` ¶

  Enable asan `alloca`/VLA protection.

`max-iterations-computation-cost` ¶

  Bound on the cost of an expression to compute the number of iterations in the doloop optimizer.

`max-isl-operations` ¶

  Maximum number of isl operations, 0 means unlimited.

`graphite-max-arrays-per-scop` ¶

  Maximum number of arrays per SCoP.

`max-vartrack-reverse-op-size` ¶

  Maximum size of variable tracking loc list for which reverse ops should be added.

`fsm-scale-path-stmts` ¶

  Scale factor to apply to the number of statements in a threading path crossing a loop back edge when comparing to `--param=max-jump-thread-duplication-stmts`.

`uninit-control-dep-attempts` ¶

  Maximum number of nested calls to search for control dependencies during uninitialized variable analysis.

`uninit-max-chain-len` ¶

  Maximum number of predicates and-ed for each predicate or-ed in the normalized predicate chain.

`uninit-max-num-chains` ¶

  Maximum number of predicates or-ed in the normalized predicate chain.

`uninit-max-prune-work` ¶

  Maximum amount of work done to prune paths where the variable is always initialized.

`sched-autopref-queue-depth` ¶

  Hardware autoprefetcher scheduler model control flag. Number of lookahead cycles the model looks into; a value of 0 only enables the instruction sorting heuristic.

`loop-versioning-max-inner-insns` ¶

  The maximum number of instructions that an inner loop can have before the loop versioning pass considers it too big to copy.

`loop-versioning-max-outer-insns` ¶

  The maximum number of instructions that an outer loop can have before the loop versioning pass considers it too big to copy, discounting any instructions in inner loops that directly benefit from versioning.

`ssa-name-def-chain-limit` ¶

  The maximum number of SSA_NAME assignments to follow in determining a property of a variable such as its value. This limits the number of iterations or recursive calls GCC performs when optimizing certain statements or when determining their validity prior to issuing diagnostics.

`store-merging-max-size` ¶

  Maximum size of a single store merging region in bytes.

`store-forwarding-max-distance` ¶

  Maximum number of instruction distance that a small store forwarded to a larger load may stall. A value of 0 disables the cost checks for the avoid-store-forwarding pass.

`hash-table-verification-limit` ¶

  The number of elements for which hash table verification is done for each searched element.

`max-find-base-term-values` ¶

  Maximum number of VALUEs handled during a single `find_base_term` call.

`analyzer-max-enodes-per-program-point` ¶

  The maximum number of exploded nodes per program point within the analyzer, before terminating analysis of that point.

`analyzer-max-constraints` ¶

  The maximum number of constraints per state.

`analyzer-min-snodes-for-call-summary` ¶

  The minimum number of supernodes within a function for the analyzer to consider summarizing its effects at call sites.

`analyzer-max-enodes-for-full-dump` ¶

  The maximum depth of exploded nodes that should appear in a dot dump before switching to a less verbose format.

`analyzer-max-recursion-depth` ¶

  The maximum number of times a callsite can appear in a call stack within the analyzer, before terminating analysis of a call that would recurse deeper.

`analyzer-max-svalue-depth` ¶

  The maximum depth of a symbolic value, before approximating the value as unknown.

`analyzer-max-infeasible-edges` ¶

  The maximum number of infeasible edges to reject before declaring a diagnostic as infeasible.

`gimple-fe-computed-hot-bb-threshold` ¶

  The number of executions of a basic block that is considered hot. The parameter is used only in GIMPLE FE.

`analyzer-bb-explosion-factor` ¶

  The maximum number of “after supernode” exploded nodes within the analyzer per supernode, before terminating analysis.

`analyzer-text-art-string-ellipsis-threshold` ¶

  The number of bytes at which to ellipsize string literals in analyzer text art diagrams.

`analyzer-text-art-ideal-canvas-width` ¶

  The ideal width in characters of text art diagrams generated by the analyzer.

`analyzer-text-art-string-ellipsis-head-len` ¶

  The number of literal bytes to show at the head of a string literal in text art when ellipsizing it.

`analyzer-text-art-string-ellipsis-tail-len` ¶

  The number of literal bytes to show at the tail of a string literal in text art when ellipsizing it.

`ranger-logical-depth` ¶

  Maximum depth of logical expression evaluation ranger looks through when evaluating outgoing edge ranges.

`ranger-recompute-depth` ¶

  Maximum depth of instruction chains to consider for recomputation in the outgoing range calculator.

`relation-block-limit` ¶

  Maximum number of relations the dominator tree oracle registers in a basic block during value range relational processing.

`transitive-relations-work-bound` ¶

  Work bound when discovering transitive relations from existing relations in value range relational processing.

`min-pagesize` ¶

  Minimum page size for warning and early break vectorization purposes.

`openacc-kernels` ¶

  Specify mode of OpenACC `kernels` constructs handling. With `--param=openacc-kernels=decompose`, OpenACC `kernels` constructs are decomposed into parts, a sequence of compute constructs, each then handled individually. This is work in progress. With `--param=openacc-kernels=parloops`, OpenACC `kernels` constructs are handled by the ‘`parloops`’ pass, en bloc. This is the current default.

`openacc-privatization` ¶

  Control whether the `-fopt-info-omp-note` and applicable `-fdump-tree-*-details` options emit OpenACC privatization diagnostics. With `--param=openacc-privatization=quiet`, don’t diagnose. This is the current default. With `--param=openacc-privatization=noisy`, do diagnose.

`cycle-accurate-model` ¶

  Specifies whether GCC should assume that the scheduling description is mostly a cycle-accurate model of the target processor the code is intended to run on, in the absence of cache misses. Nonzero means that the selected scheduling model is accurate and likely describes an in-order processor, and that scheduling should aggressively spill to try and fill any pipeline bubbles. This is the current default. Zero means the scheduling description might not be available/accurate or perhaps not applicable at all, such as for modern out-of-order processors.