https://gcc.gnu.org/g:e548eb628c689e2836e570aef98b9547aff97a02
commit r17-4377-ge548eb628c689e2836e570aef98b9547aff97a02 Author: Andrea Pinski <[email protected]> Date: Fri Sep 11 13:32:39 2026 -0700 match: x+umax(x,1) -> umax(x*2, 1) [PR127103] This adds a simplification for `x+umax(x,1)` to `umax(x*2, 1)` when `x*2` is known not to overflow. This shows up with std::vector::push_back after the patch which adds `x+minmax(a,b)` simplification; it is also a special case of that patch for `umax and 1`. This gives a small code generation improvement with std::vector::push_back because we trade an add after the umax with a shift beforehand. Bootstrapped and tested on x86_64-linux-gnu. PR tree-optimization/127103 gcc/ChangeLog: * match.pd (`x+umax(x,1)`): New pattern. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/max1-plus-1.c: New test. Signed-off-by: Andrea Pinski <[email protected]> Diff: --- gcc/match.pd | 12 ++++++++++++ gcc/testsuite/gcc.dg/tree-ssa/max1-plus-1.c | 22 ++++++++++++++++++++++ 2 files changed, 34 insertions(+) diff --git a/gcc/match.pd b/gcc/match.pd index 4059ed787f05..82cf6ae0a3c6 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -522,6 +522,18 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (if (ANY_INTEGRAL_TYPE_P (type) && TYPE_OVERFLOW_UNDEFINED (type)) (abs @0))) +#if GIMPLE +/* x + uMax(x, 1) -> uMax(x+x, 1) + if x+x is known not to wrap/overflow. */ +(simplify + (plus:c @0 (max:s@2 @0 integer_onep@1)) + (if (TYPE_UNSIGNED (type)) + (with { int_range_max vr0; } + (if (gimple_match_range_of_expr (vr0, @0, @2) + && range_op_handler (PLUS_EXPR).overflow_free_p (vr0, vr0)) + (max (plus @0 @0) @1))))) +#endif + /* X * 1, X / 1 -> X. */ (for op (mult trunc_div ceil_div floor_div round_div exact_div) (simplify diff --git a/gcc/testsuite/gcc.dg/tree-ssa/max1-plus-1.c b/gcc/testsuite/gcc.dg/tree-ssa/max1-plus-1.c new file mode 100644 index 000000000000..9fdf0a40cc48 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/max1-plus-1.c @@ -0,0 +1,22 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-optimized-raw" } */ +/* x + uMax(x, 1) -> uMax(x+x, 1) */ +/* PR tree-optimization/127103 */ + +__attribute__((always_inline)) +static inline unsigned +max(unsigned a, unsigned b) +{ + if (a < b) + return b; + return a; +} + +unsigned f1(unsigned a, unsigned t1) +{ + if (a > __INT_MAX__) + return 0; + return a + max(1, a); +} + +/* { dg-final { scan-tree-dump "gimple_assign <mult_expr, _\[0-9\], a_\[0-9\].D., 2" "optimized" } } */
