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* [Bug d/110359] New: d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435
@ 2023-06-21 18:44 ibuclaw at gcc dot gnu.org
2023-06-26 1:28 ` [Bug d/110359] " cvs-commit at gcc dot gnu.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: ibuclaw at gcc dot gnu.org @ 2023-06-21 18:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110359
Bug ID: 110359
Summary: d: Suboptimal codegen for __builtin_expect(cond,
false) since PR96435
Product: gcc
Version: 11.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: d
Assignee: ibuclaw at gdcproject dot org
Reporter: ibuclaw at gcc dot gnu.org
Target Milestone: ---
Since pr96435, both boolean objects *and* expressions have been evaluated in
the following way.
(*(ubyte*)&obj_or_expr) & 1
It has been noted that sometimes this can cause the back-end to optimize in
non-obvious ways - in particular with `__builtin_expect`.
---
double pow(in double x, in ulong p)
{
import gcc.builtins : __builtin_expect;
if (__builtin_expect(p == 0, false)) // 1,2
return 1;
if (__builtin_expect(p == 1, false)) // 3,4
return x;
double s = x;
double v = 1;
for (ulong i = p; i > 1; i >>= 1) // 5
{
v = (i & 0x1) ? s * v : v;
s = s * s;
}
return v * s;
}
---
The first 5 lines of assembly for the above function (corresponding souce line
marked in comments)
---
double example.pow(in double, in ulong):
test rdi, rdi
je .L6
cmp rdi, 1
je .L1
jbe .L1
---
The jbe condition looks like it is either redundant, or suboptimal.
This @safe feature could be restricted to just when reading the value of a bool
field that comes from a union.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug d/110359] d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435
2023-06-21 18:44 [Bug d/110359] New: d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435 ibuclaw at gcc dot gnu.org
@ 2023-06-26 1:28 ` cvs-commit at gcc dot gnu.org
2023-06-26 1:40 ` cvs-commit at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2023-06-26 1:28 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110359
--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Iain Buclaw <ibuclaw@gcc.gnu.org>:
https://gcc.gnu.org/g:ab98db1e8c1b997414539f41b7fb814019497d8d
commit r14-2082-gab98db1e8c1b997414539f41b7fb814019497d8d
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date: Mon Jun 26 03:24:27 2023 +0200
d: Suboptimal codegen for __builtin_expect(cond, false)
Since PR96435, both boolean objects and expressions have been evaluated
in the following way.
(*(ubyte*)&obj_or_expr) & 1
It has been noted that sometimes this can cause the back-end to optimize
in non-obvious ways - in particular with __builtin_expect.
This @safe feature is now restricted to just when reading the value of a
bool field that comes from a union.
PR d/110359
gcc/d/ChangeLog:
* d-convert.cc (convert_for_rvalue): Only apply the @safe boolean
conversion to boolean fields of a union.
(convert_for_condition): Call convert_for_rvalue in the default
case.
gcc/testsuite/ChangeLog:
* gdc.dg/pr110359.d: New test.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug d/110359] d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435
2023-06-21 18:44 [Bug d/110359] New: d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435 ibuclaw at gcc dot gnu.org
2023-06-26 1:28 ` [Bug d/110359] " cvs-commit at gcc dot gnu.org
@ 2023-06-26 1:40 ` cvs-commit at gcc dot gnu.org
2023-06-26 2:07 ` cvs-commit at gcc dot gnu.org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2023-06-26 1:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110359
--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Iain Buclaw
<ibuclaw@gcc.gnu.org>:
https://gcc.gnu.org/g:9599da719abe4e990fb9cb7ad9d1abc19a5f0429
commit r13-7479-g9599da719abe4e990fb9cb7ad9d1abc19a5f0429
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date: Mon Jun 26 03:24:27 2023 +0200
d: Suboptimal codegen for __builtin_expect(cond, false)
Since PR96435, both boolean objects and expressions have been evaluated
in the following way.
(*(ubyte*)&obj_or_expr) & 1
It has been noted that sometimes this can cause the back-end to optimize
in non-obvious ways - in particular with __builtin_expect.
This @safe feature is now restricted to just when reading the value of a
bool field that comes from a union.
PR d/110359
gcc/d/ChangeLog:
* d-convert.cc (convert_for_rvalue): Only apply the @safe boolean
conversion to boolean fields of a union.
(convert_for_condition): Call convert_for_rvalue in the default
case.
gcc/testsuite/ChangeLog:
* gdc.dg/pr110359.d: New test.
(cherry picked from commit ab98db1e8c1b997414539f41b7fb814019497d8d)
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug d/110359] d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435
2023-06-21 18:44 [Bug d/110359] New: d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435 ibuclaw at gcc dot gnu.org
2023-06-26 1:28 ` [Bug d/110359] " cvs-commit at gcc dot gnu.org
2023-06-26 1:40 ` cvs-commit at gcc dot gnu.org
@ 2023-06-26 2:07 ` cvs-commit at gcc dot gnu.org
2023-06-26 2:09 ` cvs-commit at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2023-06-26 2:07 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110359
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Iain Buclaw
<ibuclaw@gcc.gnu.org>:
https://gcc.gnu.org/g:0f54a73b998b72f7c8452a63730ec3b16fc47854
commit r12-9730-g0f54a73b998b72f7c8452a63730ec3b16fc47854
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date: Mon Jun 26 03:24:27 2023 +0200
d: Suboptimal codegen for __builtin_expect(cond, false)
Since PR96435, both boolean objects and expressions have been evaluated
in the following way.
(*(ubyte*)&obj_or_expr) & 1
It has been noted that sometimes this can cause the back-end to optimize
in non-obvious ways - in particular with __builtin_expect.
This @safe feature is now restricted to just when reading the value of a
bool field that comes from a union.
PR d/110359
gcc/d/ChangeLog:
* d-convert.cc (convert_for_rvalue): Only apply the @safe boolean
conversion to boolean fields of a union.
(convert_for_condition): Call convert_for_rvalue in the default
case.
gcc/testsuite/ChangeLog:
* gdc.dg/pr110359.d: New test.
(cherry picked from commit ab98db1e8c1b997414539f41b7fb814019497d8d)
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug d/110359] d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435
2023-06-21 18:44 [Bug d/110359] New: d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435 ibuclaw at gcc dot gnu.org
` (2 preceding siblings ...)
2023-06-26 2:07 ` cvs-commit at gcc dot gnu.org
@ 2023-06-26 2:09 ` cvs-commit at gcc dot gnu.org
2023-06-26 2:10 ` cvs-commit at gcc dot gnu.org
2023-06-26 2:13 ` ibuclaw at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2023-06-26 2:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110359
--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Iain Buclaw
<ibuclaw@gcc.gnu.org>:
https://gcc.gnu.org/g:a0c4bd656e0fce16d62877e0eb53ac11b1924d0c
commit r11-10875-ga0c4bd656e0fce16d62877e0eb53ac11b1924d0c
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date: Mon Jun 26 03:24:27 2023 +0200
d: Suboptimal codegen for __builtin_expect(cond, false)
Since PR96435, both boolean objects and expressions have been evaluated
in the following way.
(*(ubyte*)&obj_or_expr) & 1
It has been noted that sometimes this can cause the back-end to optimize
in non-obvious ways - in particular with __builtin_expect.
This @safe feature is now restricted to just when reading the value of a
bool field that comes from a union.
PR d/110359
gcc/d/ChangeLog:
* d-convert.cc (convert_for_rvalue): Only apply the @safe boolean
conversion to boolean fields of a union.
(convert_for_condition): Call convert_for_rvalue in the default
case.
gcc/testsuite/ChangeLog:
* gdc.dg/pr110359.d: New test.
(cherry picked from commit ab98db1e8c1b997414539f41b7fb814019497d8d)
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug d/110359] d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435
2023-06-21 18:44 [Bug d/110359] New: d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435 ibuclaw at gcc dot gnu.org
` (3 preceding siblings ...)
2023-06-26 2:09 ` cvs-commit at gcc dot gnu.org
@ 2023-06-26 2:10 ` cvs-commit at gcc dot gnu.org
2023-06-26 2:13 ` ibuclaw at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2023-06-26 2:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110359
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Iain Buclaw
<ibuclaw@gcc.gnu.org>:
https://gcc.gnu.org/g:ab134ecb05c6cf1d7a0aee58e7649a93a87c9874
commit r10-11475-gab134ecb05c6cf1d7a0aee58e7649a93a87c9874
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date: Mon Jun 26 03:24:27 2023 +0200
d: Suboptimal codegen for __builtin_expect(cond, false)
Since PR96435, both boolean objects and expressions have been evaluated
in the following way.
(*(ubyte*)&obj_or_expr) & 1
It has been noted that sometimes this can cause the back-end to optimize
in non-obvious ways - in particular with __builtin_expect.
This @safe feature is now restricted to just when reading the value of a
bool field that comes from a union.
PR d/110359
gcc/d/ChangeLog:
* d-convert.cc (convert_for_rvalue): Only apply the @safe boolean
conversion to boolean fields of a union.
(convert_for_condition): Call convert_for_rvalue in the default
case.
gcc/testsuite/ChangeLog:
* gdc.dg/pr110359.d: New test.
(cherry picked from commit ab98db1e8c1b997414539f41b7fb814019497d8d)
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug d/110359] d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435
2023-06-21 18:44 [Bug d/110359] New: d: Suboptimal codegen for __builtin_expect(cond, false) since PR96435 ibuclaw at gcc dot gnu.org
` (4 preceding siblings ...)
2023-06-26 2:10 ` cvs-commit at gcc dot gnu.org
@ 2023-06-26 2:13 ` ibuclaw at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: ibuclaw at gcc dot gnu.org @ 2023-06-26 2:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110359
ibuclaw at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|UNCONFIRMED |RESOLVED
--- Comment #6 from ibuclaw at gcc dot gnu.org ---
Fix committed.
^ permalink raw reply [flat|nested] 7+ messages in thread
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