https://gcc.gnu.org/g:7c4f8ae20cc09e8732739ac839c845ba8c2991c0
commit r16-5041-g7c4f8ae20cc09e8732739ac839c845ba8c2991c0 Author: Richard Biener <[email protected]> Date: Mon Nov 3 14:43:39 2025 +0100 Use gather_imm_use_stmts instead of FOR_EACH_IMM_USE_STMT in forwprop The following fixes forwprop using FOR_EACH_IMM_USE_STMT to iterate over stmts and then eventually removing the active stmt, releasing its defs. This can cause debug stmt insertion with a RHS referencing the SSA name we iterate over, adding to its immediate use list but also adjusting all other debug stmts refering to the released SSA name, updating those. And those can refer to the original iterated over variable. In the end the destructive behavior of update_stmt is a problem here, which unlinks all uses of a stmt and then links in the newly computed ones instead of leaving those in place that are. The solution is to not rely on FOR_EACH_IMM_USE_STMT to iterate over stmt uses without duplicates. * tree-ssa-forwprop.cc (forward_propagate_addr_expr): Use gather_imm_use_stmts instead of FOR_EACH_IMM_USE_STMT. Diff: --- gcc/tree-ssa-forwprop.cc | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc index 9a993ab04de3..67deecaf0044 100644 --- a/gcc/tree-ssa-forwprop.cc +++ b/gcc/tree-ssa-forwprop.cc @@ -925,12 +925,10 @@ forward_propagate_addr_expr_1 (tree name, tree def_rhs, static bool forward_propagate_addr_expr (tree name, tree rhs, bool parent_single_use_p) { - imm_use_iterator iter; - gimple *use_stmt; bool all = true; bool single_use_p = parent_single_use_p && has_single_use (name); - FOR_EACH_IMM_USE_STMT (use_stmt, iter, name) + for (gimple *use_stmt : gather_imm_use_stmts (name)) { bool result; tree use_rhs;
