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* [Bug other/94403] New: Missed optimization bswap
@ 2020-03-30 15:40 boris_oncev at hotmail dot com
2020-03-30 15:46 ` [Bug other/94403] " boris_oncev at hotmail dot com
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: boris_oncev at hotmail dot com @ 2020-03-30 15:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94403
Bug ID: 94403
Summary: Missed optimization bswap
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: boris_oncev at hotmail dot com
Target Milestone: ---
full code:
https://godbolt.org/z/zjNqYV
template <typename T>
auto reverse(T num) {
// misses optimization when num is int32_t OK for int64_t
auto* bytes = reinterpret_cast<char*>(&num);
// misses optimization for both 32 and 64 bit ints
//auto* bytes = reinterpret_cast<std::byte*>(&num);
constexpr auto size = sizeof(num);
for (int i = 0; i < size / 2; i++) {
std::swap(bytes[i], bytes[size-i-1]);
}
return num;
}
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug other/94403] Missed optimization bswap
2020-03-30 15:40 [Bug other/94403] New: Missed optimization bswap boris_oncev at hotmail dot com
@ 2020-03-30 15:46 ` boris_oncev at hotmail dot com
2020-03-30 16:40 ` [Bug tree-optimization/94403] " jakub at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: boris_oncev at hotmail dot com @ 2020-03-30 15:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94403
Boris <boris_oncev at hotmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #1 from Boris <boris_oncev at hotmail dot com> ---
Very similar
*** This bug has been marked as a duplicate of bug 93328 ***
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/94403] Missed optimization bswap
2020-03-30 15:40 [Bug other/94403] New: Missed optimization bswap boris_oncev at hotmail dot com
2020-03-30 15:46 ` [Bug other/94403] " boris_oncev at hotmail dot com
@ 2020-03-30 16:40 ` jakub at gcc dot gnu.org
2020-03-30 16:55 ` jakub at gcc dot gnu.org
2020-03-31 9:05 ` cvs-commit at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: jakub at gcc dot gnu.org @ 2020-03-30 16:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94403
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|other |tree-optimization
Last reconfirmed| |2020-03-30
Ever confirmed|0 |1
CC| |jakub at gcc dot gnu.org
Resolution|DUPLICATE |---
Status|RESOLVED |REOPENED
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I don't see how it is similar except that it is about bswap detection.
Your comment is weird, because bswap is detected for int32_t and not for
int64_t, while the comment suggests otherwise.
And the reason this is optimized for int32_t only is that the loop is
completely unrolled in that case, but not for int64_t, where cunrolli punts on
it even with -O2 -funroll-loops or -O3.
And, the std::byte issue is unrelated to that.
--- gcc/gimple-ssa-store-merging.c.jj 2020-03-20 09:33:03.602112329 +0100
+++ gcc/gimple-ssa-store-merging.c 2020-03-30 18:30:31.723341519 +0200
@@ -315,7 +315,8 @@ verify_symbolic_number_p (struct symboli
lhs_type = gimple_expr_type (stmt);
- if (TREE_CODE (lhs_type) != INTEGER_TYPE)
+ if (TREE_CODE (lhs_type) != INTEGER_TYPE
+ && TREE_CODE (lhs_type) != ENUMERAL_TYPE)
return false;
if (TYPE_PRECISION (lhs_type) != TYPE_PRECISION (n->type))
can fix that one.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/94403] Missed optimization bswap
2020-03-30 15:40 [Bug other/94403] New: Missed optimization bswap boris_oncev at hotmail dot com
2020-03-30 15:46 ` [Bug other/94403] " boris_oncev at hotmail dot com
2020-03-30 16:40 ` [Bug tree-optimization/94403] " jakub at gcc dot gnu.org
@ 2020-03-30 16:55 ` jakub at gcc dot gnu.org
2020-03-31 9:05 ` cvs-commit at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: jakub at gcc dot gnu.org @ 2020-03-30 16:55 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94403
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 48147
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48147&action=edit
gcc10-pr94403.patch
Untested fix for the std::byte part. Not a regression, so will have to wait
for GCC11. Also, if the testcase doesn't have the assignment of the parameter
into a separate local temporary (i.e. when the parameter itself is
addressable), then it doesn't work either, the loads stay as MEM_REFs instead
of being transformed to BIT_FIELD_REFs on the parameter.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/94403] Missed optimization bswap
2020-03-30 15:40 [Bug other/94403] New: Missed optimization bswap boris_oncev at hotmail dot com
` (2 preceding siblings ...)
2020-03-30 16:55 ` jakub at gcc dot gnu.org
@ 2020-03-31 9:05 ` cvs-commit at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2020-03-31 9:05 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94403
--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:5ea39b2412269d208bb6ebd78303815957bd4f70
commit r10-7470-g5ea39b2412269d208bb6ebd78303815957bd4f70
Author: Jakub Jelinek <jakub@redhat.com>
Date: Tue Mar 31 11:04:32 2020 +0200
store-merging: Allow enums during bswap recognition [PR94403]
The following testcase is optimized with char/unsigned char/signed char,
but not with std::byte. The following patch fixes that. Didn't use
INTEGRAL_TYPE_P because bswapping bools is just too weird.
2020-03-31 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/94403
* gimple-ssa-store-merging.c (verify_symbolic_number_p): Allow also
ENUMERAL_TYPE lhs_type.
* g++.dg/tree-ssa/pr94403.C: New test.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2020-03-31 9:05 UTC | newest]
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2020-03-30 15:40 [Bug other/94403] New: Missed optimization bswap boris_oncev at hotmail dot com
2020-03-30 15:46 ` [Bug other/94403] " boris_oncev at hotmail dot com
2020-03-30 16:40 ` [Bug tree-optimization/94403] " jakub at gcc dot gnu.org
2020-03-30 16:55 ` jakub at gcc dot gnu.org
2020-03-31 9:05 ` cvs-commit at gcc dot gnu.org
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