PR rtl-optimization/54300

[pf3gnuchains/gcc-fork.git] / gcc / regcprop.c

diff --git a/gcc/regcprop.c b/gcc/regcprop.c
index ceb4635..e5a7a48 100644 (file)
--- a/gcc/regcprop.c
+++ b/gcc/regcprop.c
@@ -741,6 +741,7 @@ copyprop_hardreg_forward_1 (basic_block bb, struct value_data *vd)
       int n_ops, i, alt, predicated;
       bool is_asm, any_replacements;
       rtx set;
+      rtx link;
       bool replaced[MAX_RECOG_OPERANDS];
       bool changed = false;
 
@@ -808,6 +809,23 @@ copyprop_hardreg_forward_1 (basic_block bb, struct value_data *vd)
        if (recog_op_alt[i][alt].earlyclobber)
          kill_value (recog_data.operand[i], vd);
 
+      /* If we have dead sets in the insn, then we need to note these as we
+        would clobbers.  */
+      for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
+       {
+         if (REG_NOTE_KIND (link) == REG_UNUSED)
+           {
+             kill_value (XEXP (link, 0), vd);
+             /* Furthermore, if the insn looked like a single-set,
+                but the dead store kills the source value of that
+                set, then we can no-longer use the plain move
+                special case below.  */
+             if (set
+                 && reg_overlap_mentioned_p (XEXP (link, 0), SET_SRC (set)))
+               set = NULL;
+           }
+       }
+
       /* Special-case plain move instructions, since we may well
         be able to do the move from a different register class.  */
       if (set && REG_P (SET_SRC (set)))