https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82524
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target| |x86_64-*-*, i?86-*-*
Priority|P3 |P2
Status|UNCONFIRMED |NEW
Known to work| |6.4.1
Last reconfirmed| |2017-10-12
Component|middle-end |rtl-optimization
CC| |segher at gcc dot gnu.org
Ever confirmed|0 |1
Summary|expensive-optimizations |[7/8 Regression]
|produces wrong results |expensive-optimizations
| |produces wrong results
Target Milestone|--- |7.3
Known to fail| |7.2.1, 8.0
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's not bswap. Looks like a RTL optimization issue to me.
--param max-combine-insns=2 fixes it for me.
> g++-7 t.C -O2 --param max-combine-insns=2
> ./a.out
A=00FFFFFF B=FFFFFFFF alphaBlend(A,B)=00FFFFFF
> g++-7 t.C -O2 --param max-combine-insns=3
> ./a.out
A=00FFFFFF B=FFFFFFFF alphaBlend(A,B)=0000FFFF
