fwprop: Avoid volatile rtx 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 singel 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.

2 files changed, 17 insertions, 0 deletions

diff --git a/gcc/fwprop.cc b/gcc/fwprop.cc
index 7872609..cb6fd67 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 0000000..07b207f
--- /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 try to be propagated.  */
+long long foo ()
+{
+  long long res;
+  __asm__ __volatile__(
+    ""
+      : "=r" (res)
+      :
+      : "memory");
+  return res;
+}