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* [Bug tree-optimization/94818] New: GCC emits dead bodies of functions whose all calls have been eliminated by optimisations
@ 2020-04-28 12:43 felix.von.s at posteo dot de
2020-04-28 13:36 ` [Bug ipa/94818] " rguenth at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: felix.von.s at posteo dot de @ 2020-04-28 12:43 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94818
Bug ID: 94818
Summary: GCC emits dead bodies of functions whose all calls
have been eliminated by optimisations
Product: gcc
Version: 10.0
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: ---
Target: x86_64-linux-gnu
In this code:
__attribute__((__warning__("argh")))
static void foo(void) {
__asm__ (
";;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;"
";;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;"
);
}
void bar0(int x) {
if (__builtin_constant_p(x))
foo();
}
void bar1(int x) {
if (__builtin_constant_p(x))
foo();
}
No calls to foo are emitted in the final output, and GCC knows this, since no
warnings are emitted. However, GCC will still emit a function body for foo,
unless either the __asm__ statement is removed or both conditions are changed
to integer constant expressions, so that the function is eliminated by one of
the inlining passes.
(I decided to demonstrate it this way instead of using
__attribute__((__noinline__)), just to make sure this is not related to
__attribute__((__noinline__)) somehow implying __attribute__((__used__)).)
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug ipa/94818] GCC emits dead bodies of functions whose all calls have been eliminated by optimisations 2020-04-28 12:43 [Bug tree-optimization/94818] New: GCC emits dead bodies of functions whose all calls have been eliminated by optimisations felix.von.s at posteo dot de @ 2020-04-28 13:36 ` rguenth at gcc dot gnu.org 2020-04-29 6:27 ` pinskia at gcc dot gnu.org 2021-07-20 22:23 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: rguenth at gcc dot gnu.org @ 2020-04-28 13:36 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94818 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Ever confirmed|0 |1 Last reconfirmed| |2020-04-28 CC| |marxin at gcc dot gnu.org Component|tree-optimization |ipa Status|UNCONFIRMED |NEW --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- Confirmed. ___builtin_constant_p is only resolved after IPA optimization and at that point unreachable functions can no longer be removed reliably (foo is output before bar0 __builtin_constant_p is resolved). We could add another "IPA" sync point before RTL expansion but not sure if we really want to. We could also see there's no callers to bar0 and bar1 and resolve __builtin_constant_p earlier during IPA. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug ipa/94818] GCC emits dead bodies of functions whose all calls have been eliminated by optimisations 2020-04-28 12:43 [Bug tree-optimization/94818] New: GCC emits dead bodies of functions whose all calls have been eliminated by optimisations felix.von.s at posteo dot de 2020-04-28 13:36 ` [Bug ipa/94818] " rguenth at gcc dot gnu.org @ 2020-04-29 6:27 ` pinskia at gcc dot gnu.org 2021-07-20 22:23 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2020-04-29 6:27 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94818 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Depends on| |47205, 89139 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Related to PR 47205, PR 89139 Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47205 [Bug 47205] GCC emits optimized out noinline function https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89139 [Bug 89139] GCC emits code for static functions that aren't used by the optimized code ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug ipa/94818] GCC emits dead bodies of functions whose all calls have been eliminated by optimisations 2020-04-28 12:43 [Bug tree-optimization/94818] New: GCC emits dead bodies of functions whose all calls have been eliminated by optimisations felix.von.s at posteo dot de 2020-04-28 13:36 ` [Bug ipa/94818] " rguenth at gcc dot gnu.org 2020-04-29 6:27 ` pinskia at gcc dot gnu.org @ 2021-07-20 22:23 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-07-20 22:23 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94818 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Severity|normal |enhancement ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-07-20 22:23 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-04-28 12:43 [Bug tree-optimization/94818] New: GCC emits dead bodies of functions whose all calls have been eliminated by optimisations felix.von.s at posteo dot de 2020-04-28 13:36 ` [Bug ipa/94818] " rguenth at gcc dot gnu.org 2020-04-29 6:27 ` pinskia at gcc dot gnu.org 2021-07-20 22:23 ` pinskia at gcc dot gnu.org
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