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combine: Fix for PR81423

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We here have an AND of a SUBREG of an LSHIFTRT.  If that SUBREG is
paradoxical, the extraction we form is the length of the size of the
inner mode, which includes some bits that should not be in the result.
Just give up in that case.


	PR rtl-optimization/81423
	* combine.c (make_compound_operation_int): Don't try to optimize
	the AND of a SUBREG of an LSHIFTRT if that SUBREG is paradoxical.

From-SVN: r250365
This commit is contained in:
Segher Boessenkool 2017-07-19 21:31:26 +02:00 • committed by Segher Boessenkool
parent a6722e5bf2
commit 6cdcce60ff
2 changed files with 9 additions and 12 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2018-07-19 Segher Boessenkool <segher@kernel.crashing.org>
PR rtl-optimization/81423
* combine.c (make_compound_operation_int): Don't try to optimize
the AND of a SUBREG of an LSHIFTRT if that SUBREG is paradoxical.
2017-07-19 Segher Boessenkool <segher@kernel.crashing.org>
PR rtl-optimization/81423

15
gcc/combine.c
View file

@ -7956,18 +7956,9 @@ make_compound_operation_int (machine_mode mode, rtx *x_ptr,
XEXP (inner_x0, 1),
i, 1, 0, in_code == COMPARE);
if (new_rtx)
{
/* If we narrowed the mode when dropping the subreg, then
we must zero-extend to keep the semantics of the AND. */
if (GET_MODE_SIZE (inner_mode) >= GET_MODE_SIZE (mode))
;
else if (SCALAR_INT_MODE_P (inner_mode))
new_rtx = simplify_gen_unary (ZERO_EXTEND, mode,
new_rtx, inner_mode);
else
new_rtx = NULL;
}
/* If we narrowed the mode when dropping the subreg, then we lose. */
if (GET_MODE_SIZE (inner_mode) < GET_MODE_SIZE (mode))
new_rtx = NULL;
/* If that didn't give anything, see if the AND simplifies on
its own. */