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* [Bug rtl-optimization/67462] New: [6 Regression] FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump ce1 "3 true changes made"
@ 2015-09-05 12:52 hjl.tools at gmail dot com
2015-09-08 8:46 ` [Bug rtl-optimization/67462] " ktkachov at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: hjl.tools at gmail dot com @ 2015-09-05 12:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67462
Bug ID: 67462
Summary: [6 Regression] FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump
ce1 "3 true changes made"
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
CC: ktkachov at gcc dot gnu.org
Target Milestone: ---
On Linux/x86-64, r227368 caused:
spawn -ignore SIGHUP /export/build/gnu/gcc-x32/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/
/export/gnu/import/git/sources/gcc/gcc/testsuite/gcc.dg/ifcvt-3.c -m32
-fno-diagnostics-show-caret -fdiagnostics-color=never -fdump-rtl-ce1 -O2
-ffat-lto-objects -S -o ifcvt-3.s
PASS: gcc.dg/ifcvt-3.c (test for excess errors)
FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump ce1 "3 true changes made"
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug rtl-optimization/67462] [6 Regression] FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump ce1 "3 true changes made"
2015-09-05 12:52 [Bug rtl-optimization/67462] New: [6 Regression] FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump ce1 "3 true changes made" hjl.tools at gmail dot com
@ 2015-09-08 8:46 ` ktkachov at gcc dot gnu.org
2015-09-08 9:05 ` [Bug target/67462] " ktkachov at gcc dot gnu.org
2015-09-14 11:00 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: ktkachov at gcc dot gnu.org @ 2015-09-08 8:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67462
ktkachov at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2015-09-08
Ever confirmed|0 |1
--- Comment #1 from ktkachov at gcc dot gnu.org ---
This is just a failure to if-convert with -m32 due to costs.
The costing logic deems it to not be profitable, which may well be a valid
decision to make. In this case, if-converting would actually always be
profitable
as the code:
s64 d = a - b;
if (d == 0)
return a + c;
else
return b + d + c;
can be simplified to just "a + c" but that's not something we can see in ifcvt
(shouldn't the tree-level optimizers catch this earlier?).
I propose to skip the testcase for -m32, what is the standard way of specifying
that in the testsuite?
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/67462] [6 Regression] FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump ce1 "3 true changes made"
2015-09-05 12:52 [Bug rtl-optimization/67462] New: [6 Regression] FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump ce1 "3 true changes made" hjl.tools at gmail dot com
2015-09-08 8:46 ` [Bug rtl-optimization/67462] " ktkachov at gcc dot gnu.org
@ 2015-09-08 9:05 ` ktkachov at gcc dot gnu.org
2015-09-14 11:00 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: ktkachov at gcc dot gnu.org @ 2015-09-08 9:05 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67462
ktkachov at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|rtl-optimization |target
--- Comment #2 from ktkachov at gcc dot gnu.org ---
IMO this is a target issue.
If you think if-conversion should happen for -m32 then the backend costs should
be fixed.
If not, then this test should be skipped.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/67462] [6 Regression] FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump ce1 "3 true changes made"
2015-09-05 12:52 [Bug rtl-optimization/67462] New: [6 Regression] FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump ce1 "3 true changes made" hjl.tools at gmail dot com
2015-09-08 8:46 ` [Bug rtl-optimization/67462] " ktkachov at gcc dot gnu.org
2015-09-08 9:05 ` [Bug target/67462] " ktkachov at gcc dot gnu.org
@ 2015-09-14 11:00 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2015-09-14 11:00 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67462
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |6.0
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
The tree level should indeed do a better job here but it gets "confused" by
narrowing the return expressions to int before it gets a chance to do
that optimization. It's
s64 d = a - b;
if (d == 0)
return (unsigned)a + (unsigned)c;
else
return (unsigned)b + (unsigned)d + (unsigned)c;
to them and 'd' is not handled the same way because the shortening happens
in the frontend.
You might want to file a separate PR about this missed optimization.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2015-09-14 11:00 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-09-05 12:52 [Bug rtl-optimization/67462] New: [6 Regression] FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump ce1 "3 true changes made" hjl.tools at gmail dot com
2015-09-08 8:46 ` [Bug rtl-optimization/67462] " ktkachov at gcc dot gnu.org
2015-09-08 9:05 ` [Bug target/67462] " ktkachov at gcc dot gnu.org
2015-09-14 11:00 ` rguenth at gcc dot gnu.org
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