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combine.c (simplify_rtx): Do not replace TRUNCATE with a SUBREG if truncation is not a no-op.

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        * combine.c (simplify_rtx): Do not replace TRUNCATE with a SUBREG if
        truncation is not a no-op.

From-SVN: r22835
This commit is contained in:
Jeff Law 1998-10-05 03:05:58 -06:00
parent f385990fce
commit 6a99221410
1 changed files with 6 additions and 3 deletions
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9
gcc/combine.c
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@ -3773,9 +3773,12 @@ simplify_rtx (x, op0_mode, last, in_dest)
return SUBREG_REG (XEXP (x, 0));
/* If we know that the value is already truncated, we can
replace the TRUNCATE with a SUBREG. */
if (num_sign_bit_copies (XEXP (x, 0), GET_MODE (XEXP (x, 0)))
>= GET_MODE_BITSIZE (mode) + 1)
replace the TRUNCATE with a SUBREG if TRULY_NOOP_TRUNCATION is
nonzero for the corresponding modes. */
if (TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0))))
&& num_sign_bit_copies (XEXP (x, 0), GET_MODE (XEXP (x, 0)))
>= GET_MODE_BITSIZE (mode) + 1)
return gen_lowpart_for_combine (mode, XEXP (x, 0));
/* A truncate of a comparison can be replaced with a subreg if