* [PATCH] combine: Don't create (set (reg:CC) (compare (reg:CC) (const0)))
@ 2015-05-11 13:13 Segher Boessenkool
2015-05-11 17:23 ` Jeff Law
2015-05-13 11:38 ` Segher Boessenkool
0 siblings, 2 replies; 5+ messages in thread
From: Segher Boessenkool @ 2015-05-11 13:13 UTC (permalink / raw)
To: gcc-patches; +Cc: rth, Segher Boessenkool
There already was code to just use the original reg:CC, but it was
positioned incorrectly: if the original code (that this RTL is
simplified from) did not already start with a COMPARE (or not in
the right mode), it didn't trigger. But it is valid in that case
as well.
This then allows merging the other two arms of this conditional;
do so.
Bootstrapped and regression tested on powerpc64-linux and x86_64-linux;
no regressions. Also built toolchains and Linux kernels for every
arch where that works; no new failures on that.
Any objections?
Segher
2015-05-11 Segher Boessenkool <segher@kernel.crashing.org>
* combine.c (simplify_set): When generating a CC set, if the
source already is in the correct mode, do not wrap it in a
compare. Simplify the rest of that code.
---
gcc/combine.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
diff --git a/gcc/combine.c b/gcc/combine.c
index 896d9d2..51f78a5 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -6675,20 +6675,16 @@ simplify_set (rtx x)
if (other_changed)
undobuf.other_insn = other_insn;
- /* Otherwise, if we didn't previously have a COMPARE in the
- correct mode, we need one. */
- if (GET_CODE (src) != COMPARE || GET_MODE (src) != compare_mode)
- {
- SUBST (SET_SRC (x), gen_rtx_COMPARE (compare_mode, op0, op1));
- src = SET_SRC (x);
- }
- else if (GET_MODE (op0) == compare_mode && op1 == const0_rtx)
+ /* Don't generate a compare of a CC with 0, just use that CC. */
+ if (GET_MODE (op0) == compare_mode && op1 == const0_rtx)
{
SUBST (SET_SRC (x), op0);
src = SET_SRC (x);
}
- /* Otherwise, update the COMPARE if needed. */
- else if (XEXP (src, 0) != op0 || XEXP (src, 1) != op1)
+ /* Otherwise, if we didn't previously have the same COMPARE we
+ want, create it from scratch. */
+ else if (GET_CODE (src) != COMPARE || GET_MODE (src) != compare_mode
+ || XEXP (src, 0) != op0 || XEXP (src, 1) != op1)
{
SUBST (SET_SRC (x), gen_rtx_COMPARE (compare_mode, op0, op1));
src = SET_SRC (x);
--
1.8.1.4
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] combine: Don't create (set (reg:CC) (compare (reg:CC) (const0)))
2015-05-11 13:13 [PATCH] combine: Don't create (set (reg:CC) (compare (reg:CC) (const0))) Segher Boessenkool
@ 2015-05-11 17:23 ` Jeff Law
2015-05-11 21:11 ` Segher Boessenkool
2015-05-13 11:38 ` Segher Boessenkool
1 sibling, 1 reply; 5+ messages in thread
From: Jeff Law @ 2015-05-11 17:23 UTC (permalink / raw)
To: Segher Boessenkool, gcc-patches; +Cc: rth
On 05/11/2015 07:13 AM, Segher Boessenkool wrote:
> There already was code to just use the original reg:CC, but it was
> positioned incorrectly: if the original code (that this RTL is
> simplified from) did not already start with a COMPARE (or not in
> the right mode), it didn't trigger. But it is valid in that case
> as well.
>
> This then allows merging the other two arms of this conditional;
> do so.
>
> Bootstrapped and regression tested on powerpc64-linux and x86_64-linux;
> no regressions. Also built toolchains and Linux kernels for every
> arch where that works; no new failures on that.
>
> Any objections?
>
>
> Segher
>
>
> 2015-05-11 Segher Boessenkool <segher@kernel.crashing.org>
>
> * combine.c (simplify_set): When generating a CC set, if the
> source already is in the correct mode, do not wrap it in a
> compare. Simplify the rest of that code.
Seems reasonable. Might not hurt to do a little testing on a cc0 target
though.
jeff
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] combine: Don't create (set (reg:CC) (compare (reg:CC) (const0)))
2015-05-11 17:23 ` Jeff Law
@ 2015-05-11 21:11 ` Segher Boessenkool
2015-05-11 21:16 ` Jeff Law
0 siblings, 1 reply; 5+ messages in thread
From: Segher Boessenkool @ 2015-05-11 21:11 UTC (permalink / raw)
To: Jeff Law; +Cc: gcc-patches, rth
On Mon, May 11, 2015 at 11:23:47AM -0600, Jeff Law wrote:
> > * combine.c (simplify_set): When generating a CC set, if the
> > source already is in the correct mode, do not wrap it in a
> > compare. Simplify the rest of that code.
> Seems reasonable. Might not hurt to do a little testing on a cc0 target
> though.
I tested on mn10300, cris, and m68k. On m68k it triggers while
building libgcc (for 040). I verified the transform is correct.
I don't have a setup to actually bootstrap or regression check
any cc0 target. A recurring theme :-(
Segher
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] combine: Don't create (set (reg:CC) (compare (reg:CC) (const0)))
2015-05-11 21:11 ` Segher Boessenkool
@ 2015-05-11 21:16 ` Jeff Law
0 siblings, 0 replies; 5+ messages in thread
From: Jeff Law @ 2015-05-11 21:16 UTC (permalink / raw)
To: Segher Boessenkool; +Cc: gcc-patches, rth
On 05/11/2015 03:11 PM, Segher Boessenkool wrote:
> On Mon, May 11, 2015 at 11:23:47AM -0600, Jeff Law wrote:
>>> * combine.c (simplify_set): When generating a CC set, if the
>>> source already is in the correct mode, do not wrap it in a
>>> compare. Simplify the rest of that code.
>> Seems reasonable. Might not hurt to do a little testing on a cc0 target
>> though.
>
> I tested on mn10300, cris, and m68k. On m68k it triggers while
> building libgcc (for 040). I verified the transform is correct.
Seems reasonable to me.
>
> I don't have a setup to actually bootstrap or regression check
> any cc0 target. A recurring theme :-(
Understood. As I mentioned in IRC and in another thread, it may be
useful to set up an aranym instance for m68k bootstrap testing in the
compile farm.
For other targets, building foo-elf in a single tree build with
binutils, newlib and the simulator, then running the gcc testsuite with
the simulator is often a good alternative. Probably wise to run through
this once or twice just to get familiar with it, then pull it out when
really needed ;)
jeff
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] combine: Don't create (set (reg:CC) (compare (reg:CC) (const0)))
2015-05-11 13:13 [PATCH] combine: Don't create (set (reg:CC) (compare (reg:CC) (const0))) Segher Boessenkool
2015-05-11 17:23 ` Jeff Law
@ 2015-05-13 11:38 ` Segher Boessenkool
1 sibling, 0 replies; 5+ messages in thread
From: Segher Boessenkool @ 2015-05-13 11:38 UTC (permalink / raw)
To: gcc-patches; +Cc: rth
On Mon, May 11, 2015 at 06:13:40AM -0700, Segher Boessenkool wrote:
> * combine.c (simplify_set): When generating a CC set, if the
> source already is in the correct mode, do not wrap it in a
> compare. Simplify the rest of that code.
Committed now.
Segher
^ permalink raw reply [flat|nested] 5+ messages in thread
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2015-05-11 13:13 [PATCH] combine: Don't create (set (reg:CC) (compare (reg:CC) (const0))) Segher Boessenkool
2015-05-11 17:23 ` Jeff Law
2015-05-11 21:11 ` Segher Boessenkool
2015-05-11 21:16 ` Jeff Law
2015-05-13 11:38 ` Segher Boessenkool
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