source: scripts/patches/gcc-4.0.0-reload_check_uninitialized_pseudos_PR20973.patch@ 63b3dd5

gcc/gcc/reload.c

@@ -1520 +1520 @@
      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 +1534 @@
             && 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 +2002 @@
                                 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];