re PR rtl-optimization/54900 (write introduction incorrect wrt the C11 memory model (2))

	PR rtl-optimization/54900
	* ifcvt.c (noce_can_store_speculate_p): Call
	memory_must_be_modified_in_insn_p.
	* alias.c (memory_must_be_modified_in_insn_p): New.
	(set_dest_equal_p): New.
	* rtl.h (memory_must_be_modified_in_p): Protoize.

From-SVN: r192548

1 files changed, 33 insertions, 0 deletions

diff --git a/gcc/alias.c b/gcc/alias.c
index 244ca52..c5e6417 100644
--- a/gcc/alias.c
+++ b/gcc/alias.c
@@ -2762,6 +2762,39 @@ memory_modified_in_insn_p (const_rtx mem, const_rtx insn)
   return memory_modified;
 }
 
+/* Return TRUE if the destination of a set is rtx identical to
+   ITEM.  */
+static inline bool
+set_dest_equal_p (const_rtx set, const_rtx item)
+{
+  rtx dest = SET_DEST (set);
+  return rtx_equal_p (dest, item);
+}
+
+/* Like memory_modified_in_insn_p, but return TRUE if INSN will
+   *DEFINITELY* modify the memory contents of MEM.  */
+bool
+memory_must_be_modified_in_insn_p (const_rtx mem, const_rtx insn)
+{
+  if (!INSN_P (insn))
+    return false;
+  insn = PATTERN (insn);
+  if (GET_CODE (insn) == SET)
+    return set_dest_equal_p (insn, mem);
+  else if (GET_CODE (insn) == PARALLEL)
+    {
+      int i;
+      for (i = 0; i < XVECLEN (insn, 0); i++)
+	{
+	  rtx sub = XVECEXP (insn, 0, i);
+	  if (GET_CODE (sub) == SET
+	      &&  set_dest_equal_p (sub, mem))
+	    return true;
+	}
+    }
+  return false;
+}
+
 /* Initialize the aliasing machinery.  Initialize the REG_KNOWN_VALUE
    array.  */