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* [Bug tree-optimization/95799] New: Assumed conjunctions are not broken down into clauses if their pureness is checked first
@ 2020-06-21 9:26 felix.von.s at posteo dot de
2020-06-22 7:59 ` [Bug tree-optimization/95799] " felix.von.s at posteo dot de
0 siblings, 1 reply; 2+ messages in thread
From: felix.von.s at posteo dot de @ 2020-06-21 9:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95799
Bug ID: 95799
Summary: Assumed conjunctions are not broken down into clauses
if their pureness is checked first
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: felix.von.s at posteo dot de
Target Milestone: ---
In the attached sample, foo is compiled into returning a constant 1, while bar
will compare a to 0, even though bar’s assumption implies foo’s.
If I replace __builtin_pure_p() testing with a constant 1, both functions
compile to the same assembly code, returning a constant 1. If I change bar to
return (a >= 0 && b >= 0), it also compiles to returning a constant 1.
It seems as if the optimiser becomes unaware that conjunction elimination is a
valid rule of inference if the conjunction’s pureness is checked first.
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug tree-optimization/95799] Assumed conjunctions are not broken down into clauses if their pureness is checked first
2020-06-21 9:26 [Bug tree-optimization/95799] New: Assumed conjunctions are not broken down into clauses if their pureness is checked first felix.von.s at posteo dot de
@ 2020-06-22 7:59 ` felix.von.s at posteo dot de
0 siblings, 0 replies; 2+ messages in thread
From: felix.von.s at posteo dot de @ 2020-06-22 7:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95799
--- Comment #1 from felix <felix.von.s at posteo dot de> ---
Created attachment 48767
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48767&action=edit
Sample program
I was pretty sure I attached this before. Never mind, here it is.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2020-06-21 9:26 [Bug tree-optimization/95799] New: Assumed conjunctions are not broken down into clauses if their pureness is checked first felix.von.s at posteo dot de
2020-06-22 7:59 ` [Bug tree-optimization/95799] " felix.von.s at posteo dot de
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