(try_combine): Don't split a PARALLEL of a SIGN_EXTEND and the object being...

(try_combine): Don't split a PARALLEL of a SIGN_EXTEND and the object
being sign extended if we have made assumptions about the form the
I2DEST.

From-SVN: r5184

diff --git a/gcc/combine.c b/gcc/combine.c
index af83df5cf8300f9891fc7ae8eaec0146a5a31da6..4a91a3f4751eb19cdab7fd907a1f3f7f2e226a82 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -1825,7 +1825,11 @@ try_combine (i3, i2, i1)
      we have a PARALLEL with both loads from the same memory location.
      We can split this into a load from memory followed by a register-register
      copy.  This saves at least one insn, more if register allocation can
-     eliminate the copy.  */
+     eliminate the copy.
+
+     We cannot do this if the destination of the second assignment is
+     a register that we have already assumed is zero-extended.  Similarly
+     for a SUBREG of such a register.  */
 
   else if (i1 && insn_code_number < 0 && asm_noperands (newpat) < 0
           && GET_CODE (newpat) == PARALLEL
@@ -1839,6 +1843,21 @@ try_combine (i3, i2, i1)
                                   INSN_CUID (i2))
           && GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) != ZERO_EXTRACT
           && GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) != STRICT_LOW_PART
+          && ! (temp = SET_DEST (XVECEXP (newpat, 0, 1)),
+                (GET_CODE (temp) == REG
+                 && reg_nonzero_bits[REGNO (temp)] != 0
+                 && GET_MODE_BITSIZE (GET_MODE (temp)) < BITS_PER_WORD
+                 && GET_MODE_BITSIZE (GET_MODE (temp)) < HOST_BITS_PER_INT
+                 && (reg_nonzero_bits[REGNO (temp)]
+                     != GET_MODE_MASK (word_mode))))
+          && ! (GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) == SUBREG
+                && (temp = SUBREG_REG (SET_DEST (XVECEXP (newpat, 0, 1))),
+                    (GET_CODE (temp) == REG
+                     && reg_nonzero_bits[REGNO (temp)] != 0
+                     && GET_MODE_BITSIZE (GET_MODE (temp)) < BITS_PER_WORD
+                     && GET_MODE_BITSIZE (GET_MODE (temp)) < HOST_BITS_PER_INT
+                     && (reg_nonzero_bits[REGNO (temp)]
+                         != GET_MODE_MASK (word_mode)))))
           && ! reg_overlap_mentioned_p (SET_DEST (XVECEXP (newpat, 0, 1)),
                                         SET_SRC (XVECEXP (newpat, 0, 1)))
           && ! find_reg_note (i3, REG_UNUSED,