https://gcc.gnu.org/g:88b9e82a4429373468b65ccbe7fde86bec3f697b
commit r17-1755-g88b9e82a4429373468b65ccbe7fde86bec3f697b Author: Andrew Pinski <[email protected]> Date: Sun Jun 21 16:10:15 2026 -0700 phiopt: Reject instead of assert that the 2 vuse of the loads are the same [PR125923] So it turns out I thought we would always get a virtual phi when there was a store in front of the load. This is correct for all normal code except if heading into an infinite loop where there are no stores/loads. Since this is leading to an infinite loop, rejecting this case does not change performance at all. Bootstrapped and tested on x86_64-linux-gnu. PR tree-optimization/125923 gcc/ChangeLog: * tree-ssa-phiopt.cc (factor_out_conditional_load): Change assert of the vuse being the same to rejecting if they are different without a virtual phi. gcc/testsuite/ChangeLog: * gcc.dg/torture/pr125923-1.c: New test. Signed-off-by: Andrew Pinski <[email protected]> Diff: --- gcc/testsuite/gcc.dg/torture/pr125923-1.c | 12 ++++++++++++ gcc/tree-ssa-phiopt.cc | 7 +++++-- 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/gcc/testsuite/gcc.dg/torture/pr125923-1.c b/gcc/testsuite/gcc.dg/torture/pr125923-1.c new file mode 100644 index 000000000000..1edce7d388fa --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr125923-1.c @@ -0,0 +1,12 @@ +/* { dg-do compile } */ +/* { dg-additional-options "-fno-tree-dce" } */ +/* PR tree-optimization/125923 */ + +int a, b, c, d; +void e() { + d = a && d; + if (b) + b = 0; + while (!a || b) + c ^= 1; +} diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc index c73a81c41668..7a623fc4c0c2 100644 --- a/gcc/tree-ssa-phiopt.cc +++ b/gcc/tree-ssa-phiopt.cc @@ -3713,8 +3713,11 @@ factor_out_conditional_load (edge e0, edge e1, basic_block merge, gphi *phi, || gimple_vuse (load1) != gimple_phi_arg_def (vphi, e1->dest_idx)) return false; } - else - gcc_assert (gimple_vuse (load0) == gimple_vuse (load1)); + /* Sometimes due to not removing dead statements, + a virtual phi does not show up going into an infinite loop + so just reject that case. */ + else if (gimple_vuse (load0) != gimple_vuse (load1)) + return false; tree ref0 = gimple_assign_rhs1 (load0); tree ref1 = gimple_assign_rhs1 (load1);
