Re: [Bug target/20126] [3.3/3.4/4.0 Regression] Inlined memcmp makes one argument null on entry

[Jakub Jelinek <jakub at redhat dot com>]

On Tue, Apr 12, 2005 at 05:54:58PM -0000, mmitchel at gcc dot gnu dot org wrote:
> 
> ------- Additional Comments From mmitchel at gcc dot gnu dot org  2005-04-12 17:54 -------
> I like the simpler approach.  If someone would test that for 4.0, I'd be ecstatic.

Here is what I have bootstrapped/regtested on
{i386,x86_64,ia64,ppc,ppc64,s390,s390x}-linux.

2005-04-13  Alexandre Oliva  <aoliva@redhat.com>
	    Roger Sayle  <roger@eyesopen.com>

	PR target/20126
	* loop.c (loop_givs_rescan): If replacement of DEST_ADDR failed,
	set the original address pseudo to the correct value before the
	original insn, if possible, and leave the insn alone, otherwise
	create a new pseudo, set it and replace it in the insn.
	* recog.c (validate_change_maybe_volatile): New.
	* recog.h (validate_change_maybe_volatile): Declare.

	* gcc.dg/pr20126.c: New.

--- gcc/loop.c.jj	2005-04-03 10:33:24.000000000 +0200
+++ gcc/loop.c	2005-04-12 23:22:06.000000000 +0200
@@ -5478,9 +5478,20 @@ loop_givs_rescan (struct loop *loop, str
 	mark_reg_pointer (v->new_reg, 0);
 
       if (v->giv_type == DEST_ADDR)
-	/* Store reduced reg as the address in the memref where we found
-	   this giv.  */
-	validate_change (v->insn, v->location, v->new_reg, 0);
+	{
+	  /* Store reduced reg as the address in the memref where we found
+	     this giv.  */
+	  if (!validate_change (v->insn, v->location, v->new_reg, 0))
+	    {
+	      if (loop_dump_stream)
+		fprintf (loop_dump_stream,
+			 "unable to reduce iv to register in insn %d\n",
+			 INSN_UID (v->insn));
+	      bl->all_reduced = 0;
+	      v->ignore = 1;
+	      continue;
+	    }
+	}
       else if (v->replaceable)
 	{
 	  reg_map[REGNO (v->dest_reg)] = v->new_reg;
--- gcc/testsuite/gcc.dg/pr20126.c	1 Jan 1970 00:00:00 -0000
+++ gcc/testsuite/gcc.dg/pr20126.c 10 Mar 2005 11:24:16 -0000
@@ -0,0 +1,50 @@
+/* dg-do run */
+/* dg-options "-O2" */
+
+/* PR target/20126 was not really target-specific, but rather a loop's
+   failure to take into account the possibility that a DEST_ADDR giv
+   replacement might fail, such as when you attempt to replace a REG
+   with a PLUS in one of the register_operands of cmpstrqi_rex_1.  */
+
+extern void abort (void);
+
+typedef struct { int a; char b[3]; } S;
+S c = { 2, "aa" }, d = { 2, "aa" };
+
+void *
+bar (const void *x, int y, int z)
+{
+  return (void *) 0;
+}
+
+int
+foo (S *x, S *y)
+{
+  const char *e, *f, *g;
+  int h;
+
+  h = y->a;
+  f = y->b;
+  e = x->b;
+
+  if (h == 1)
+    return bar (e, *f, x->a) != 0;
+
+  g = e + x->a - h;
+  while (e <= g)
+    {
+      const char *t = e + 1;
+      if (__builtin_memcmp (e, f, h) == 0)
+	return 1;
+      e = t;
+    }
+  return 0;
+}
+
+int
+main (void)
+{
+  if (foo (&c, &d) != 1)
+    abort ();
+  return 0;
+}


	Jakub