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combine.c (combine_simplify_rtx): If nonzero_bits on op shows all bits zero in mode of a lowpart subreg, return zero.

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* combine.c (combine_simplify_rtx) <case SUBREG>: If nonzero_bits
	on op shows all bits zero in mode of a lowpart subreg, return zero.

From-SVN: r198595
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Jakub Jelinek 2013-05-04 14:41:52 +02:00 committed by Jakub Jelinek
parent 71871e37d9
commit 40de22d6f9
2 changed files with 16 additions and 0 deletions
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gcc/ChangeLog
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@ -1,3 +1,8 @@
2013-05-04 Jakub Jelinek <jakub@redhat.com>
* combine.c (combine_simplify_rtx) <case SUBREG>: If nonzero_bits
on op shows all bits zero in mode of a lowpart subreg, return zero.
2013-05-03 Michael Meissner <meissner@linux.vnet.ibm.com>
PR target/57150

11
gcc/combine.c
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@ -5417,6 +5417,17 @@ combine_simplify_rtx (rtx x, enum machine_mode op0_mode, int in_dest,
SUBREG_BYTE (x));
if (temp)
return temp;
/* If op is known to have all lower bits zero, the result is zero. */
if (!in_dest
&& SCALAR_INT_MODE_P (mode)
&& SCALAR_INT_MODE_P (op0_mode)
&& GET_MODE_PRECISION (mode) < GET_MODE_PRECISION (op0_mode)
&& subreg_lowpart_offset (mode, op0_mode) == SUBREG_BYTE (x)
&& HWI_COMPUTABLE_MODE_P (op0_mode)
&& (nonzero_bits (SUBREG_REG (x), op0_mode)
& GET_MODE_MASK (mode)) == 0)
return CONST0_RTX (mode);
}
/* Don't change the mode of the MEM if that would change the meaning