OpenE2K/gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

combine: Convert subreg-of-lshiftrt to zero_extract properly (PR78390)

Browse Source 
r242414, for PR77881, introduces some bugs (PR78390, PR78438, PR78477).
It all has the same root cause: that patch makes combine convert every
lowpart subreg of a logical shift right to a zero_extract.  This cannot
work at all if it is not a constant shift, and it has to be a bit more
careful exactly which bits it extracts.


	PR target/77881
	PR bootstrap/78390
	PR target/78438
	PR bootstrap/78477
	* combine.c (make_compound_operation_int): Do not convert a subreg of
	a non-constant logical shift right to a zero_extract.  Handle the case
	where some zero bits have been shifted into the range covered by that
	subreg.

From-SVN: r242757
This commit is contained in:
Segher Boessenkool 2016-11-23 15:33:13 +01:00 committed by Segher Boessenkool
parent 33951763a8
commit 712871dde1
2 changed files with 17 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
gcc/ChangeLog
View File

@ -1,3 +1,14 @@
2016-11-23 Segher Boessenkool <segher@kernel.crashing.org>
PR target/77881
PR bootstrap/78390
PR target/78438
PR bootstrap/78477
* combine.c (make_compound_operation_int): Do not convert a subreg of
a non-constant logical shift right to a zero_extract. Handle the case
where some zero bits have been shifted into the range covered by that
subreg.
2016-11-23 Richard Sandiford <richard.sandiford@arm.com>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>

7
gcc/combine.c
View File

@ -8089,12 +8089,17 @@ make_compound_operation_int (machine_mode mode, rtx *x_ptr,
/* If the SUBREG is masking of a logical right shift,
make an extraction. */
if (GET_CODE (inner) == LSHIFTRT
&& CONST_INT_P (XEXP (inner, 1))
&& GET_MODE_SIZE (mode) < GET_MODE_SIZE (GET_MODE (inner))
&& subreg_lowpart_p (x))
{
new_rtx = make_compound_operation (XEXP (inner, 0), next_code);
int width = GET_MODE_PRECISION (GET_MODE (inner))
- INTVAL (XEXP (inner, 1));
if (width > mode_width)
width = mode_width;
new_rtx = make_extraction (mode, new_rtx, 0, XEXP (inner, 1),
mode_width, 1, 0, in_code == COMPARE);
width, 1, 0, in_code == COMPARE);
break;
}