https://gcc.gnu.org/g:8f3242ce5c03c30f806f54ceaff2a15d6e5b5ee6
commit r16-5146-g8f3242ce5c03c30f806f54ceaff2a15d6e5b5ee6 Author: Jakub Jelinek <[email protected]> Date: Tue Nov 11 08:29:22 2025 +0100 gimplify-me: Fix regimplification of gimple-reg-type clobbers [PR122620] Since r11-2238-ge443d8213864ac337c29092d4767224f280d2062 the C++ FE emits clobbers like *_1 = {CLOBBER}; where *_1 MEM_REF has some scalar type like int for -flifetime-dse={1,2} and most of the compiler manages to cope with that. If we are very unlucky, we trigger an ICE while trying to regimplify it (at least during inlining), as happens with GCC 15.2 on firefox-145.0 built with LTO+PGO. I haven't managed to reduce that to a small testcase that would ICE though, the clobber certainly appears in code like template <typename T> struct S { T *p; union { char a; T b; }; static S foo (T *x) { S s; s.p = x; s.b.~T (); return s; } ~S (); }; void bar () { int i = 42; S <int> s = S <int>::foo (&i); } but convincing inliner that it should id->regimplify = true; on exactly that stmt has been difficult. The ICE is because we try (in two spots) to regimplify the rhs of the gimple_clobber_p stmt if gimple-reg-type type (i.e. the TREE_CLOBBER), because it doesn't satisfy the is_gimple_mem_rhs_or_call predicate returned by rhs_predicate_for for the MEM_REF lhs. And regimplify it by trying to gimplify SSA_NAME = {CLOBBER}; INIT_EXPR and in there reach a special case which stores that freshly made SSA_NAME into memory and loads it from memory, so uses a SSA_NAME without SSA_NAME_DEF_STMT. Fixed thusly by saying clobbers are ok even for the gimple-reg-types. 2025-11-11 Jakub Jelinek <[email protected]> PR lto/122620 * gimplify-me.cc (gimple_regimplify_operands): Don't try to regimplify TREE_CLOBBER on rhs of gimple_clobber_p if it has gimple_reg_type. Diff: --- gcc/gimplify-me.cc | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/gcc/gimplify-me.cc b/gcc/gimplify-me.cc index 5b4b98763731..1e5056b7e579 100644 --- a/gcc/gimplify-me.cc +++ b/gcc/gimplify-me.cc @@ -233,9 +233,13 @@ gimple_regimplify_operands (gimple *stmt, gimple_stmt_iterator *gsi_p) else if (i == 2 && gimple_assign_single_p (stmt) && num_ops == 2) - gimplify_expr (&op, &pre, NULL, - rhs_predicate_for (gimple_assign_lhs (stmt)), - fb_rvalue); + { + if (gimple_clobber_p (stmt)) + continue; + gimplify_expr (&op, &pre, NULL, + rhs_predicate_for (gimple_assign_lhs (stmt)), + fb_rvalue); + } else if (i == 2 && is_gimple_call (stmt)) { if (TREE_CODE (op) == FUNCTION_DECL) @@ -254,8 +258,9 @@ gimple_regimplify_operands (gimple *stmt, gimple_stmt_iterator *gsi_p) { bool need_temp = false; - if (gimple_assign_single_p (stmt) - && num_ops == 2) + if (gimple_clobber_p (stmt)) + ; + else if (gimple_assign_single_p (stmt) && num_ops == 2) gimplify_expr (gimple_assign_rhs1_ptr (stmt), &pre, NULL, rhs_predicate_for (gimple_assign_lhs (stmt)), fb_rvalue);
