[PATCH] Fix -fcompare-debug issue in cross-jumping (PR rtl-optimization/65980)

Jakub Jelinek jakub@redhat.com
Mon Dec 14 20:15:00 GMT 2015


Hi!

rtx_renumbered_equal_p considers two LABEL_REFs equivalent if they
have the same next_real_insn, unfortunately next_real_insn doesn't ignore
debug insns.  It ignores BARRIERs/JUMP_TABLE_DATA insns too, which is IMHO
not desirable either, so this patch uses next_nonnote_nondebug_insn instead
(which stops at CODE_LABEL) and keeps iterating if CODE_LABELs are found.

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

2015-12-14  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/65980
	* jump.c (rtx_renumbered_equal_p) <case LABEL_REF>: Use
	next_nonnote_nondebug_insn instead of next_real_insn and
	skip over CODE_LABELs too.

	* gcc.dg/pr65980.c: New test.

--- gcc/jump.c.jj	2015-11-04 11:12:18.000000000 +0100
+++ gcc/jump.c	2015-12-14 17:17:08.859741360 +0100
@@ -1802,8 +1802,16 @@ rtx_renumbered_equal_p (const_rtx x, con
 
       /* Two label-refs are equivalent if they point at labels
 	 in the same position in the instruction stream.  */
-      return (next_real_insn (LABEL_REF_LABEL (x))
-	      == next_real_insn (LABEL_REF_LABEL (y)));
+      else
+	{
+	  rtx_insn *xi = next_nonnote_nondebug_insn (LABEL_REF_LABEL (x));
+	  rtx_insn *yi = next_nonnote_nondebug_insn (LABEL_REF_LABEL (y));
+	  while (xi && LABEL_P (xi))
+	    xi = next_nonnote_nondebug_insn (xi);
+	  while (yi && LABEL_P (yi))
+	    yi = next_nonnote_nondebug_insn (yi);
+	  return xi == yi;
+	}
 
     case SYMBOL_REF:
       return XSTR (x, 0) == XSTR (y, 0);
--- gcc/testsuite/gcc.dg/pr65980.c.jj	2015-12-14 17:07:54.398479666 +0100
+++ gcc/testsuite/gcc.dg/pr65980.c	2015-12-14 17:08:32.616950620 +0100
@@ -0,0 +1,30 @@
+/* PR rtl-optimization/65980 */
+/* { dg-do compile } */
+/* { dg-options "-O3 -fcompare-debug" } */
+
+typedef struct { int b; } A;
+void (*a) (int);
+int b;
+
+int
+foo (A *v)
+{
+  asm goto ("" : : "m" (v->b) : : l);
+  return 0;
+l:
+  return 1;
+}
+
+int
+bar (void)
+{
+  if (b)
+    {
+      if (foo (0) && a)
+	a (0);
+      return 0;
+    }
+  if (foo (0) && a)
+    a (0);
+  return 0;
+}

	Jakub



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