(instantiate_virtual_regs_1, case PLUS): If offset is

zero, make sure register replacement is still validated.

From-SVN: r8649

diff --git a/gcc/function.c b/gcc/function.c
index ba1265b3acec6cc76db6f390e913b197896156f7..6dfc17cac1df5fdb466e229c4b2ee98f38fbc067 100644 (file)
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -2675,7 +2675,7 @@ instantiate_virtual_regs_1 (loc, object, extra_insns)
       /* Handle special case of virtual register plus constant.  */
       if (CONSTANT_P (XEXP (x, 1)))
        {
-         rtx old;
+         rtx old, new_offset;
 
          /* Check for (plus (plus VIRT foo) (const_int)) first.  */
          if (GET_CODE (XEXP (x, 0)) == PLUS)
@@ -2722,18 +2722,26 @@ instantiate_virtual_regs_1 (loc, object, extra_insns)
              return 1;
            }
 
-         old = XEXP (x, 0);
-         XEXP (x, 0) = new;
-         new = plus_constant (XEXP (x, 1), offset);
+         new_offset = plus_constant (XEXP (x, 1), offset);
 
-         /* If the new constant is zero, try to replace the sum with its
-            first operand.  */
-         if (new == const0_rtx
-             && validate_change (object, loc, XEXP (x, 0), 0))
+         /* If the new constant is zero, try to replace the sum with just
+            the register.  */
+         if (new_offset == const0_rtx
+             && validate_change (object, loc, new, 0))
            return 1;
 
-         /* Next try to replace constant with new one.  */
-         if (!validate_change (object, &XEXP (x, 1), new, 0))
+         /* Next try to replace the register and new offset.
+            There are two changes to validate here and we can't assume that
+            in the case of old offset equals new just changing the register
+            will yield a valid insn.  In the interests of a little efficiency,
+            however, we only call validate change once (we don't queue up the
+            changes and then call apply_change_group). */
+
+         old = XEXP (x, 0);
+         if (offset == 0
+             ? ! validate_change (object, &XEXP (x, 0), new, 0)
+             : (XEXP (x, 0) = new,
+                ! validate_change (object, &XEXP (x, 1), new_offset, 0)))
            {
              if (! extra_insns)
                {
@@ -2744,15 +2752,16 @@ instantiate_virtual_regs_1 (loc, object, extra_insns)
              /* Otherwise copy the new constant into a register and replace
                 constant with that register.  */
              temp = gen_reg_rtx (Pmode);
+             XEXP (x, 0) = new;
              if (validate_change (object, &XEXP (x, 1), temp, 0))
-               emit_insn_before (gen_move_insn (temp, new), object);
+               emit_insn_before (gen_move_insn (temp, new_offset), object);
              else
                {
                  /* If that didn't work, replace this expression with a
                     register containing the sum.  */
 
-                 new = gen_rtx (PLUS, Pmode, XEXP (x, 0), new);
                  XEXP (x, 0) = old;
+                 new = gen_rtx (PLUS, Pmode, new, new_offset);
 
                  start_sequence ();
                  temp = force_operand (new, NULL_RTX);