combine.c (simplify_comparison): When widening modes, ignore sign extension on CONST_...

	* combine.c (simplify_comparison): When widening modes, ignore
	sign extension on CONST_INTs.

From-SVN: r51216

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e2a2102..b95a707 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2002-03-23  Alan Modra  <amodra@bigpond.net.au>
+
+       * combine.c (simplify_comparison): When widening modes, ignore
+       sign extension on CONST_INTs.
+
 2002-03-22  Bob Wilson  <bob.wilson@acm.org>
 
        * config/xtensa/xtensa.c (print_operand): Fix incorrect mode

diff --git a/gcc/combine.c b/gcc/combine.c
index 0f17559..88495a6 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -10975,14 +10975,22 @@ simplify_comparison (code, pop0, pop1)
         tmode = GET_MODE_WIDER_MODE (tmode))
       if (have_insn_for (COMPARE, tmode))
        {
+         int zero_extended;
+
          /* If the only nonzero bits in OP0 and OP1 are those in the
             narrower mode and this is an equality or unsigned comparison,
             we can use the wider mode.  Similarly for sign-extended
             values, in which case it is true for all comparisons.  */
-         if (((code == EQ || code == NE
-               || code == GEU || code == GTU || code == LEU || code == LTU)
-              && (nonzero_bits (op0, tmode) & ~GET_MODE_MASK (mode)) == 0
-              && (nonzero_bits (op1, tmode) & ~GET_MODE_MASK (mode)) == 0)
+         zero_extended = ((code == EQ || code == NE
+                           || code == GEU || code == GTU
+                           || code == LEU || code == LTU)
+                          && (nonzero_bits (op0, tmode)
+                              & ~GET_MODE_MASK (mode)) == 0
+                          && ((GET_CODE (op1) == CONST_INT
+                               || (nonzero_bits (op1, tmode)
+                                   & ~GET_MODE_MASK (mode)) == 0)));
+
+         if (zero_extended
              || ((num_sign_bit_copies (op0, tmode)
                   > GET_MODE_BITSIZE (tmode) - GET_MODE_BITSIZE (mode))
                  && (num_sign_bit_copies (op1, tmode)
@@ -10999,6 +11007,8 @@ simplify_comparison (code, pop0, pop1)
                                                           XEXP (op0, 1)));
 
              op0 = gen_lowpart_for_combine (tmode, op0);
+             if (zero_extended && GET_CODE (op1) == CONST_INT)
+               op1 = GEN_INT (INTVAL (op1) & GET_MODE_MASK (mode));
              op1 = gen_lowpart_for_combine (tmode, op1);
              break;
            }