Hi, This patch tries to fix a potential problem which is raised by the patch for PR111267. The volatile asm operand tries to be propagated to a single set insn with the patch for PR111267. The volatile asm operand might be executed for multiple times if the define insn isn't eliminated after propagation. Now set_src_cost comparison might reject such propagation. But it has the chance to be taken after replacing set_src_cost with insn cost. Actually I found the problem in testing my patch which replacing set_src_cost with insn_cost in fwprop pass.
Compared to the last version, the check volatile_insn_p is replaced with volatile_refs_p in order to check volatile memory reference also. https://gcc.gnu.org/pipermail/gcc-patches/2024-February/646482.html Bootstrapped and tested on x86 and powerpc64-linux BE and LE with no regressions. Is it OK for the trunk? Thanks Gui Haochen ChangeLog fwprop: Avoid volatile defines to be propagated The patch for PR111267 (commit id 86de9b66480b710202a2898cf513db105d8c432f) which introduces an exception for propagation on single set insn. The propagation which might not be profitable (checked by profitable_p) is still allowed to be propagated to single set insn. It has a potential problem that a volatile operand might be propagated to a single set insn. If the define insn is not eliminated after propagation, the volatile operand will be executed for multiple times. This patch fixes the problem by skipping volatile set source rtx in propagation. gcc/ * fwprop.cc (forward_propagate_into): Return false for volatile set source rtx. gcc/testsuite/ * gcc.target/powerpc/fwprop-1.c: New. patch.diff diff --git a/gcc/fwprop.cc b/gcc/fwprop.cc index 7872609b336..cb6fd6700ca 100644 --- a/gcc/fwprop.cc +++ b/gcc/fwprop.cc @@ -854,6 +854,8 @@ forward_propagate_into (use_info *use, bool reg_prop_only = false) rtx dest = SET_DEST (def_set); rtx src = SET_SRC (def_set); + if (volatile_refs_p (src)) + return false; /* Allow propagations into a loop only for reg-to-reg copies, since replacing one register by another shouldn't increase the cost. diff --git a/gcc/testsuite/gcc.target/powerpc/fwprop-1.c b/gcc/testsuite/gcc.target/powerpc/fwprop-1.c new file mode 100644 index 00000000000..07b207f980c --- /dev/null +++ b/gcc/testsuite/gcc.target/powerpc/fwprop-1.c @@ -0,0 +1,15 @@ +/* { dg-do compile } */ +/* { dg-options "-O1 -fdump-rtl-fwprop1-details" } */ +/* { dg-final { scan-rtl-dump-not "propagating insn" "fwprop1" } } */ + +/* Verify that volatile asm operands doesn't be propagated. */ +long long foo () +{ + long long res; + __asm__ __volatile__( + "" + : "=r" (res) + : + : "memory"); + return res; +}
