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* [Bug tree-optimization/104292] New: [missed optimization] boolean addition generates suboptimal code
@ 2022-01-30 18:34 avi at scylladb dot com
2022-01-30 18:36 ` [Bug tree-optimization/104292] " avi at scylladb dot com
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: avi at scylladb dot com @ 2022-01-30 18:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104292
Bug ID: 104292
Summary: [missed optimization] boolean addition generates
suboptimal code
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: avi at scylladb dot com
Target Milestone: ---
bool bool_or(bool b1, bool b2) {
return b1 + b2;
}
generates
bool_or(bool, bool):
movzbl %dil, %edi
movzbl %sil, %esi
addl %esi, %edi
setne %al
ret
Whereas it could generate
bool_or(bool, bool):
or %edi, %esi
mov %esi, %eax
ret
For a net gain of two instructions (and the final mov can often be elided, so
up to three).
I encountered this while using std::plus<> with boolean types. It could be
optimized as a specialization of std::plus, but I think a magic transformation
in the optimizer would make it apply in more places.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/104292] [missed optimization] boolean addition generates suboptimal code
2022-01-30 18:34 [Bug tree-optimization/104292] New: [missed optimization] boolean addition generates suboptimal code avi at scylladb dot com
@ 2022-01-30 18:36 ` avi at scylladb dot com
2022-01-30 20:02 ` pinskia at gcc dot gnu.org
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: avi at scylladb dot com @ 2022-01-30 18:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104292
--- Comment #1 from Avi Kivity <avi at scylladb dot com> ---
btw, I see that the equivalent bool_and generates optimal code.
bool_and(bool, bool):
movl %esi, %eax
andl %edi, %eax
ret
Perhaps bool is written with the expectation that any non-zero value is true?
But aren't non-zero values other than 1 undefined behavior?
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/104292] [missed optimization] boolean addition generates suboptimal code
2022-01-30 18:34 [Bug tree-optimization/104292] New: [missed optimization] boolean addition generates suboptimal code avi at scylladb dot com
2022-01-30 18:36 ` [Bug tree-optimization/104292] " avi at scylladb dot com
@ 2022-01-30 20:02 ` pinskia at gcc dot gnu.org
2022-01-30 20:05 ` pinskia at gcc dot gnu.org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-01-30 20:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104292
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
Keywords| |missed-optimization
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/104292] [missed optimization] boolean addition generates suboptimal code
2022-01-30 18:34 [Bug tree-optimization/104292] New: [missed optimization] boolean addition generates suboptimal code avi at scylladb dot com
2022-01-30 18:36 ` [Bug tree-optimization/104292] " avi at scylladb dot com
2022-01-30 20:02 ` pinskia at gcc dot gnu.org
@ 2022-01-30 20:05 ` pinskia at gcc dot gnu.org
2022-01-30 22:29 ` pinskia at gcc dot gnu.org
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-01-30 20:05 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104292
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2022-01-30
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed, I thought I saw one which was asking about bool + bool == 2 also ...
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/104292] [missed optimization] boolean addition generates suboptimal code
2022-01-30 18:34 [Bug tree-optimization/104292] New: [missed optimization] boolean addition generates suboptimal code avi at scylladb dot com
` (2 preceding siblings ...)
2022-01-30 20:05 ` pinskia at gcc dot gnu.org
@ 2022-01-30 22:29 ` pinskia at gcc dot gnu.org
2023-06-23 0:45 ` [Bug tree-optimization/104292] (bool)(bool0 + bool1) should be simplified into bool0 | bool1 pinskia at gcc dot gnu.org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-01-30 22:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104292
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=101703
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Found it, PR 101703.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/104292] (bool)(bool0 + bool1) should be simplified into bool0 | bool1
2022-01-30 18:34 [Bug tree-optimization/104292] New: [missed optimization] boolean addition generates suboptimal code avi at scylladb dot com
` (3 preceding siblings ...)
2022-01-30 22:29 ` pinskia at gcc dot gnu.org
@ 2023-06-23 0:45 ` pinskia at gcc dot gnu.org
2023-06-23 0:45 ` pinskia at gcc dot gnu.org
2024-05-09 14:56 ` pinskia at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-06-23 0:45 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104292
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This should do it I think:
(for neeq (ne eq)
(simplify
(neeq (plus zero_one_valued_p@0 zero_one_valued_p@1) INTEGER_CST@2)
(with {
tree_code newcode = ERROR_MARK;
bool notatend = false;
tree cst1 = build_one_cst (type);
wide_int cst = wi::to_wide (@2);
// a + b == 2 -> a & b
// a + b != 2 -> ~(a & b)
if (cst == 2)
newcode = BIT_AND_EXPR, notatend = neeq == NE_EXPR;
// a + b == 1 -> a ^ b
// a + b != 1 -> ~(a ^ b) -> a == b
else if (cst == 1)
newcode = BIT_XOR_EXPR, notatend = neeq == NE_EXPR;
// a + b == 0 -> ~(a | b)
// a + b != 0 -> a | b
else if (cst == 0)
newcode = BIT_IOR_EXPR, notatend = neeq == EQ_EXPR;
}
(if (notatend)
(switch
(if (newcode == BIT_IOR_EXPR)
(bit_xor (bit_ior @0 @1) { cst1; }))
(if (newcode == BIT_AND_EXPR)
(bit_xor (bit_and @0 @1) { cst1; }))
(if (newcode == BIT_XOR_EXPR)
(eq @0 @1)))
(switch
(if (newcode == BIT_IOR_EXPR)
(bit_ior @0 @1))
(if (newcode == BIT_AND_EXPR)
(bit_and @0 @1))
(if (newcode == BIT_XOR_EXPR)
(bit_xor @0 @1)))
)
)
)
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/104292] (bool)(bool0 + bool1) should be simplified into bool0 | bool1
2022-01-30 18:34 [Bug tree-optimization/104292] New: [missed optimization] boolean addition generates suboptimal code avi at scylladb dot com
` (4 preceding siblings ...)
2023-06-23 0:45 ` [Bug tree-optimization/104292] (bool)(bool0 + bool1) should be simplified into bool0 | bool1 pinskia at gcc dot gnu.org
@ 2023-06-23 0:45 ` pinskia at gcc dot gnu.org
2024-05-09 14:56 ` pinskia at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-06-23 0:45 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104292
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot gnu.org
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/104292] (bool)(bool0 + bool1) should be simplified into bool0 | bool1
2022-01-30 18:34 [Bug tree-optimization/104292] New: [missed optimization] boolean addition generates suboptimal code avi at scylladb dot com
` (5 preceding siblings ...)
2023-06-23 0:45 ` pinskia at gcc dot gnu.org
@ 2024-05-09 14:56 ` pinskia at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-05-09 14:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104292
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note LLVM started to do this "trick" in 17.1.0.
^ permalink raw reply [flat|nested] 8+ messages in thread
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2022-01-30 18:36 ` [Bug tree-optimization/104292] " avi at scylladb dot com
2022-01-30 20:02 ` pinskia at gcc dot gnu.org
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