[PATCH] Fix up ix86_expand_set_or_movmem (PR target/61060)

[Jakub Jelinek]

Hi!

As discussed in the PR, ix86_expand_set_or_movmem assumes that count == 0
means !CONST_INT_P (count_exp), but that is not necessarily true with
-O0 -ftree-ter, when the middle-end doesn't immediately see the length
argument be integer_zerop, yet TER results in it being expanded as
const0_rtx.

There is nothing to set or move in that case, so this patch makes the
backend more tolerand just by returning true immediately.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2014-05-12  Jakub Jelinek  <ja...@redhat.com>

        PR target/61060
        * config/i386/i386.c (ix86_expand_set_or_movmem): If count_exp
        is const0_rtx, return immediately.  Don't test count == 0 when
        it is always true.

        * gcc.dg/pr61060.c: New test.

--- gcc/config/i386/i386.c.jj   2014-05-11 22:21:28.000000000 +0200
+++ gcc/config/i386/i386.c      2014-05-12 10:59:18.940416162 +0200
@@ -24156,8 +24156,13 @@ ix86_expand_set_or_movmem (rtx dst, rtx
     align = MEM_ALIGN (dst) / BITS_PER_UNIT;
 
   if (CONST_INT_P (count_exp))
-    min_size = max_size = probable_max_size = count = expected_size
-      = INTVAL (count_exp);
+    {
+      min_size = max_size = probable_max_size = count = expected_size
+       = INTVAL (count_exp);
+      /* When COUNT is 0, there is nothing to do.  */
+      if (!count)
+       return true;
+    }
   else
     {
       if (min_size_exp)
@@ -24166,7 +24171,7 @@ ix86_expand_set_or_movmem (rtx dst, rtx
        max_size = INTVAL (max_size_exp);
       if (probable_max_size_exp)
        probable_max_size = INTVAL (probable_max_size_exp);
-      if (CONST_INT_P (expected_size_exp) && count == 0)
+      if (CONST_INT_P (expected_size_exp))
        expected_size = INTVAL (expected_size_exp);
      }
 
--- gcc/testsuite/gcc.dg/pr61060.c.jj   2014-05-12 11:03:10.797222337 +0200
+++ gcc/testsuite/gcc.dg/pr61060.c      2014-05-12 11:03:02.882263281 +0200
@@ -0,0 +1,19 @@
+/* PR target/61060 */
+/* { dg-do compile } */
+/* { dg-options "-O0 -ftree-ter" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+extern inline __attribute__ ((gnu_inline, always_inline, artificial))
+void *memset (void *dest, int ch, size_t len)
+{
+  return __builtin_memset (dest, ch, len);
+}
+
+char buf[10];
+
+void
+foo (void)
+{
+  memset (buf, sizeof (buf), 0);
+}

        Jakub