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* [Bug middle-end/105638] New: Redundant stores aren't removed by DSE
@ 2022-05-17 23:29 hjl.tools at gmail dot com
2022-05-18 12:42 ` [Bug middle-end/105638] " rguenth at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: hjl.tools at gmail dot com @ 2022-05-17 23:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105638
Bug ID: 105638
Summary: Redundant stores aren't removed by DSE
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
Target Milestone: ---
For
$ cat foo.cpp
#include <stdint.h>
#include <vector>
#include <tr1/array>
class FastBoard {
public:
typedef std::pair<int, int> movescore_t;
typedef std::tr1::array<movescore_t, 24> scoredlist_t;
protected:
std::vector<int> m_critical;
int m_boardsize;
};
class FastState {
public:
FastBoard board;
int movenum;
protected:
FastBoard::scoredlist_t scoredmoves;
};
class KoState : public FastState {
private:
std::vector<uint64_t> ko_hash_history;
std::vector<uint64_t> hash_history;
};
class GameState : public KoState {
public:
void foo ();
private:
std::vector<KoState> game_history;
};
void GameState::foo() {
game_history.resize(movenum);
}
$ g++ -O2 -march=skylake foo.cpp -S
generates:
...
movl $280, %edx
xorl %esi, %esi
call memset
movq %rax, %rcx
vpxor %xmm0, %xmm0, %xmm0
addq $280, %rcx
vmovdqu %xmm0, 36(%rax)
vmovdqu %xmm0, 52(%rax)
vmovdqu %xmm0, 68(%rax)
vmovdqu %xmm0, 84(%rax)
vmovdqu %xmm0, 100(%rax)
vmovdqu %xmm0, 116(%rax)
vmovdqu %xmm0, 132(%rax)
vmovdqu %xmm0, 148(%rax)
vmovdqu %xmm0, 164(%rax)
vmovdqu %xmm0, 180(%rax)
vmovdqu %xmm0, 196(%rax)
vmovdqu %xmm0, 212(%rax)
...
Here memset has cleared 280 bytes starting from RAX. There is no need to
clear these bytes again. The optimized tree dump shows:
<bb 14> [local count: 444773291]:
# __cur_154 = PHI <__cur_42(14), _6(13)>
# __n_155 = PHI <__n_41(14), __n_20(D)(13)>
*__cur_154 = {};
MEM[(int * *)__cur_154] = 0B;
MEM[(int * *)__cur_154 + 8B] = 0B;
MEM[(int * *)__cur_154 + 16B] = 0B;
MEM[(struct array *)__cur_154 + 36B]._M_instance = {};
MEM <vector(4) long unsigned int> [(long unsigned int * *)__cur_154 + 232B] =
{ 0, 0, 0, 0 };
MEM[(long unsigned int * *)__cur_154 + 264B] = 0B;
MEM[(long unsigned int * *)__cur_154 + 272B] = 0B;
Some of them are removed by RTL DSE. But vector stores aren't. Should
SSA DSE remove them?
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/105638] Redundant stores aren't removed by DSE
2022-05-17 23:29 [Bug middle-end/105638] New: Redundant stores aren't removed by DSE hjl.tools at gmail dot com
@ 2022-05-18 12:42 ` rguenth at gcc dot gnu.org
2022-06-01 21:23 ` cvs-commit at gcc dot gnu.org
2022-06-14 13:53 ` hjl.tools at gmail dot com
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-05-18 12:42 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105638
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2022-05-18
Ever confirmed|0 |1
Keywords| |missed-optimization
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
DSE doesn't remove redundant stores, in some cases it can prune an earlier
store but that's only handled in a limited set of cases. The issue with
removing redundant stores is that side-effects on the effective dynamic type
have to be preserved so removing earlier stores is much better.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/105638] Redundant stores aren't removed by DSE
2022-05-17 23:29 [Bug middle-end/105638] New: Redundant stores aren't removed by DSE hjl.tools at gmail dot com
2022-05-18 12:42 ` [Bug middle-end/105638] " rguenth at gcc dot gnu.org
@ 2022-06-01 21:23 ` cvs-commit at gcc dot gnu.org
2022-06-14 13:53 ` hjl.tools at gmail dot com
2 siblings, 0 replies; 4+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-06-01 21:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105638
--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by H.J. Lu <hjl@gcc.gnu.org>:
https://gcc.gnu.org/g:a743a72714fc4a9d7036d28d0cacdf2a3621f629
commit r13-921-ga743a72714fc4a9d7036d28d0cacdf2a3621f629
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Wed May 18 13:00:47 2022 -0700
DSE: Use the constant store source if possible
RTL DSE tracks redundant constant stores within a basic block. When RTL
loop invariant motion hoists a constant initialization out of the loop
into a separate basic block, the constant store value becomes unknown
within the original basic block. When recording store for RTL DSE, check
if the source register is set only once to a constant by a non-partial
unconditional load. If yes, record the constant as the constant store
source. It eliminates unrolled zero stores after memset 0 in a loop
where a vector register is used as the zero store source.
gcc/
PR rtl-optimization/105638
* df-core.cc (df_find_single_def_src): Moved and renamed from
find_single_def_src in loop-iv.cc. Change the argument to rtx
and use rtx_equal_p. Return null for partial or conditional
defs.
* df.h (df_find_single_def_src): New prototype.
* dse.cc (record_store): Use the constant source if the source
register is set only once.
* loop-iv.cc (find_single_def_src): Moved to df-core.cc.
(replace_single_def_regs): Replace find_single_def_src with
df_find_single_def_src.
gcc/testsuite/
PR rtl-optimization/105638
* g++.target/i386/pr105638.C: New test.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/105638] Redundant stores aren't removed by DSE
2022-05-17 23:29 [Bug middle-end/105638] New: Redundant stores aren't removed by DSE hjl.tools at gmail dot com
2022-05-18 12:42 ` [Bug middle-end/105638] " rguenth at gcc dot gnu.org
2022-06-01 21:23 ` cvs-commit at gcc dot gnu.org
@ 2022-06-14 13:53 ` hjl.tools at gmail dot com
2 siblings, 0 replies; 4+ messages in thread
From: hjl.tools at gmail dot com @ 2022-06-14 13:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105638
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|NEW |RESOLVED
Target Milestone|--- |13.0
--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> ---
Fixed.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-05-17 23:29 [Bug middle-end/105638] New: Redundant stores aren't removed by DSE hjl.tools at gmail dot com
2022-05-18 12:42 ` [Bug middle-end/105638] " rguenth at gcc dot gnu.org
2022-06-01 21:23 ` cvs-commit at gcc dot gnu.org
2022-06-14 13:53 ` hjl.tools at gmail dot com
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