From: Richard Sandiford <rsandifo@nildram.co.uk>
Date: Thu, 22 Nov 2007 09:27:55 +0000 (+0000)
Subject: re PR rtl-optimization/33848 (reference to non-existent label at -O1 on mips/mipsel)
X-Git-Tag: prereleases/gcc-4.2.3-rc1~119
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6ec9ca44db73c08584bc54ae523f1a9b9ad86c78;p=thirdparty%2Fgcc.git

re PR rtl-optimization/33848 (reference to non-existent label at -O1 on mips/mipsel)

gcc/
	PR rtl-optimization/33848
	* reload.c (subst_reloads): When replacing a LABEL_REF with a
	register, only add a REG_LABEL note if the label is the target
	of the jump.

gcc/testsuite/
	PR rtl-optimization/33848
	* gcc.dg/torture/pr33848.c: New test.

From-SVN: r130344
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 17e62103e6da..63f136354f02 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2007-11-22  Richard Sandiford  <rsandifo@nildram.co.uk>
+
+	PR rtl-optimization/33848
+	* reload.c (subst_reloads): When replacing a LABEL_REF with a
+	register, only add a REG_LABEL note if the label is the target
+	of the jump.
+
 2007-11-16  Richard Guenther  <rguenther@suse.de>
 
 	PR middle-end/34030
diff --git a/gcc/reload.c b/gcc/reload.c
index 501fe849d4b9..5fb0f09e0f95 100644
--- a/gcc/reload.c
+++ b/gcc/reload.c
@@ -6158,17 +6158,16 @@ subst_reloads (rtx insn)
 	    }
 #endif /* ENABLE_CHECKING */
 
-	  /* If we're replacing a LABEL_REF with a register, add a
-	     REG_LABEL note to indicate to flow which label this
+	  /* If we're replacing a LABEL_REF jump target with a register,
+	     add a REG_LABEL note to indicate to flow which label this
 	     register refers to.  */
 	  if (GET_CODE (*r->where) == LABEL_REF
-	      && JUMP_P (insn))
-	    {
-	      REG_NOTES (insn) = gen_rtx_INSN_LIST (REG_LABEL,
-						    XEXP (*r->where, 0),
-						    REG_NOTES (insn));
-	      JUMP_LABEL (insn) = XEXP (*r->where, 0);
-	   }
+	      && JUMP_P (insn)
+	      && JUMP_LABEL (insn) == XEXP (*r->where, 0)
+	      && !find_reg_note (insn, REG_LABEL, XEXP (*r->where, 0)))
+	    REG_NOTES (insn) = gen_rtx_INSN_LIST (REG_LABEL,
+						  XEXP (*r->where, 0),
+						  REG_NOTES (insn));
 
 	  /* Encapsulate RELOADREG so its machine mode matches what
 	     used to be there.  Note that gen_lowpart_common will
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 71a148318fb2..1aef4f96bd53 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2007-11-22  Richard Sandiford  <rsandifo@nildram.co.uk>
+
+	PR rtl-optimization/33848
+	* gcc.dg/torture/pr33848.c: New test.
+
 2007-11-16  Richard Guenther  <rguenther@suse.de>
 
 	PR middle-end/34030
diff --git a/gcc/testsuite/gcc.dg/torture/pr33848.c b/gcc/testsuite/gcc.dg/torture/pr33848.c
new file mode 100644
index 000000000000..c3b85e9e576b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr33848.c
@@ -0,0 +1,43 @@
+/* &&foo should be hoisted, but on most targets, excess register pressure
+   forces it to be rematerialized before "data != &&foo".  On targets that
+   have a "branch if registers are equal" instruction, this leads to the
+   branch having two LABEL_REFs: one for the branch target and one for
+   &&foo.  When reloading &&foo into a register, reload would wrongly
+   say that &&foo was the target of the branch, and the real target would
+   then be removed as dead.  */
+/* { dg-do link } */
+#define NVARS 30
+#define MULTI(X) \
+  X( 0), X( 1), X( 2), X( 3), X( 4), X( 5), X( 6), X( 7), X( 8), X( 9), \
+  X(10), X(11), X(12), X(13), X(14), X(15), X(16), X(17), X(18), X(19), \
+  X(20), X(21), X(22), X(23), X(24), X(25), X(26), X(27), X(28), X(29)
+
+#define DECLARE(INDEX) i##INDEX = gv[INDEX]
+#define COPY(INDEX) gv[INDEX] = i##INDEX
+
+volatile int gv[NVARS];
+void *volatile data;
+
+int
+main (void)
+{
+  __label__ foo;
+
+  if (gv[0] == 1)
+    goto foo;
+  data = &&foo;
+  do
+    {
+      int MULTI (DECLARE);
+      MULTI (COPY);
+      MULTI (COPY);
+      MULTI (COPY);
+      if (data != &&foo)
+	gv[0] = 1;
+      else
+	gv[1] = 2;
+    }
+  while (gv[0] > 0);
+ foo:
+  return 0;
+}