source: scripts/patches/gcc-4.0.0-reload_check_uninitialized_pseudos_PR20973.patch @ a7d67ca

Submitted by: Ryan Oliver <ryan.oliver@pha.com.au>
Source: http://gcc.gnu.org/ml/gcc-cvs/2005-04/msg01085.html
Initial Package Version: 4.0.0
Upstream Status: In gcc4 mainline
Description:

2005-04-20  Michael Matz  <matz@suse.de>

       PR20973
       * reload.c (push_reload, find_dummy_reload): Check for uninitialized
       pseudos.

===================================================================
RCS file: /cvs/gcc/gcc/gcc/reload.c,v
retrieving revision 1.268
retrieving revision 1.269
diff -u -r1.268 -r1.269
--- gcc/gcc/reload.c    2005/02/24 22:06:06     1.268
+++ gcc/gcc/reload.c    2005/04/20 14:30:38     1.269
@@ -1520,7 +1520,7 @@
      But if there is no spilling in this block, that is OK.
      An explicitly used hard reg cannot be a spill reg.  */
 
-  if (rld[i].reg_rtx == 0 && in != 0)
+  if (rld[i].reg_rtx == 0 && in != 0 && hard_regs_live_known)
     {
       rtx note;
       int regno;
@@ -1534,6 +1534,11 @@
            && REG_P (XEXP (note, 0))
            && (regno = REGNO (XEXP (note, 0))) < FIRST_PSEUDO_REGISTER
            && reg_mentioned_p (XEXP (note, 0), in)
+           /* Check that we don't use a hardreg for an uninitialized
+              pseudo.  See also find_dummy_reload().  */
+           && (ORIGINAL_REGNO (XEXP (note, 0)) < FIRST_PSEUDO_REGISTER
+               || ! bitmap_bit_p (ENTRY_BLOCK_PTR->global_live_at_end,
+                                  ORIGINAL_REGNO (XEXP (note, 0))))
            && ! refers_to_regno_for_reload_p (regno,
                                               (regno
                                                + hard_regno_nregs[regno]
@@ -1997,7 +2002,17 @@
                                is a subreg, and in that case, out
                                has a real mode.  */
                             (GET_MODE (out) != VOIDmode
-                             ? GET_MODE (out) : outmode)))
+                             ? GET_MODE (out) : outmode))
+        /* But only do all this if we can be sure, that this input
+           operand doesn't correspond with an uninitialized pseudoreg.
+           global can assign some hardreg to it, which is the same as
+          a different pseudo also currently live (as it can ignore the
+          conflict).  So we never must introduce writes to such hardregs,
+          as they would clobber the other live pseudo using the same.
+          See also PR20973.  */
+      && (ORIGINAL_REGNO (in) < FIRST_PSEUDO_REGISTER
+          || ! bitmap_bit_p (ENTRY_BLOCK_PTR->global_live_at_end,
+                            ORIGINAL_REGNO (in))))
     {
       unsigned int regno = REGNO (in) + in_offset;
       unsigned int nwords = hard_regno_nregs[regno][inmode];