https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113985
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |NEW
Keywords| |internal-improvement
Ever confirmed|0 |1
Component|rtl-optimization |middle-end
Severity|normal |enhancement
Summary|redundant copy of return |expansion of `*struct =
|values at O0 |call();` could be improved
Resolution|INVALID |---
Last reconfirmed| |2024-02-19
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Just for reference this comes from the expansion of *b = call.
What is happening is it is loading the original variable from *b and then
ioring the new value in. This should be improved but not because of the -O0
case but rather it would be better for expansion reasons and better initial
RTL.
Not we normally don't care about -O0 code size/generation but in this case, it
just that it would help improve compile time slightly.
I have not looked fully into what produces the tmp = (a&0) just yet though.
But the initial RTL (even at -O2) is:
```
(insn 28 27 29 (set (reg:SI 112)
(mem/c:SI (reg/f:DI 110) [1 g_91D.2780+8 S4 A64]))
"/app/example.cpp":27:8 -1
(nil))
(insn 29 28 30 (parallel [
(set (reg:SI 113)
(and:SI (reg:SI 112)
(const_int 0 [0])))
(clobber (reg:CC 17 flags))
]) "/app/example.cpp":27:8 -1
(nil))
(insn 30 29 31 (parallel [
(set (reg:SI 114)
(ior:SI (reg:SI 113)
(reg:SI 111)))
(clobber (reg:CC 17 flags))
]) "/app/example.cpp":27:8 -1
(nil))
```
Which seems like it definitely could be improved.
