[backport gcc-4.8/trunk r193453 <mikpe@it.uu.se>]

gcc/

2012-11-12  Steven Bosscher  <steven@gcc.gnu.org>
	    Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/51447
	* df-scan.c (df_get_entry_block_def_set): Add global regs to the set.
	* df-problems.c (df_lr_local_compute): Make global regs always live.
	* dce.c (deletable_insn_p): Make insns setting a global reg
	inherently necessary.

gcc/testsuite/

2012-11-12  Steven Bosscher  <steven@gcc.gnu.org>
	    Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/51447
	* gcc.c-torture/execute/pr51447.c: New test.

--- gcc-4.6.3/gcc/dce.c.~1~	2011-01-19 16:13:01.000000000 +0100
+++ gcc-4.6.3/gcc/dce.c	2012-11-16 16:52:36.000000000 +0100
@@ -94,6 +94,7 @@ deletable_insn_p (rtx insn, bool fast, b
 {
   rtx body, x;
   int i;
+  df_ref *def_rec;
 
   if (CALL_P (insn)
       /* We cannot delete calls inside of the recursive dce because
@@ -117,6 +118,12 @@ deletable_insn_p (rtx insn, bool fast, b
   if (!insn_nothrow_p (insn))
     return false;
 
+  /* If INSN sets a global_reg, leave it untouched.  */
+  for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
+    if (HARD_REGISTER_NUM_P (DF_REF_REGNO (*def_rec))
+	&& global_regs[DF_REF_REGNO (*def_rec)])
+      return false;
+
   body = PATTERN (insn);
   switch (GET_CODE (body))
     {
--- gcc-4.6.3/gcc/df-problems.c.~1~	2011-07-07 21:10:01.000000000 +0200
+++ gcc-4.6.3/gcc/df-problems.c	2012-11-16 16:52:03.000000000 +0100
@@ -893,7 +893,7 @@ df_lr_bb_local_compute (unsigned int bb_
 static void
 df_lr_local_compute (bitmap all_blocks ATTRIBUTE_UNUSED)
 {
-  unsigned int bb_index;
+  unsigned int bb_index, i;
   bitmap_iterator bi;
 
   bitmap_clear (&df->hardware_regs_used);
@@ -901,6 +901,11 @@ df_lr_local_compute (bitmap all_blocks A
   /* The all-important stack pointer must always be live.  */
   bitmap_set_bit (&df->hardware_regs_used, STACK_POINTER_REGNUM);
 
+  /* Global regs are always live, too.  */
+  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+    if (global_regs[i])
+      bitmap_set_bit (&df->hardware_regs_used, i);
+
   /* Before reload, there are a few registers that must be forced
      live everywhere -- which might not already be the case for
      blocks within infinite loops.  */
--- gcc-4.6.3/gcc/df-scan.c.~1~	2011-02-02 21:08:06.000000000 +0100
+++ gcc-4.6.3/gcc/df-scan.c	2012-11-16 16:52:03.000000000 +0100
@@ -3732,6 +3732,8 @@ df_get_entry_block_def_set (bitmap entry
 
   for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
     {
+      if (global_regs[i])
+	bitmap_set_bit (entry_block_defs, i);
       if (FUNCTION_ARG_REGNO_P (i))
 #ifdef INCOMING_REGNO
 	bitmap_set_bit (entry_block_defs, INCOMING_REGNO (i));
--- gcc-4.6.3/gcc/testsuite/gcc.c-torture/execute/pr51447.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6.3/gcc/testsuite/gcc.c-torture/execute/pr51447.c	2012-11-16 16:52:03.000000000 +0100
@@ -0,0 +1,27 @@
+/* PR rtl-optimization/51447 */
+
+extern void abort (void);
+
+#ifdef __x86_64__
+register void *ptr asm ("rbx");
+#else
+void *ptr;
+#endif
+
+int
+main (void)
+{
+  __label__ nonlocal_lab;
+  __attribute__((noinline, noclone)) void
+    bar (void *func)
+      {
+	ptr = func;
+	goto nonlocal_lab;
+      }
+  bar (&&nonlocal_lab);
+  return 1;
+nonlocal_lab:
+  if (ptr != &&nonlocal_lab)
+    abort ();
+  return 0;
+}