https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81558
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rguenth at gcc dot gnu.org
Blocks| |53947
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
The inner loop in foo2 is completely unrolled by GCC and imgY_org[y][x] is
_32 = (long unsigned int) y_103;
_33 = _32 * 8;
_34 = imgY_org.8_31 + _33;
_35 = *_34;
where *_34 aliases *orgptr. Thus it's not possible to vectorize this without
a runtime alias check. The innermost loop in foo1 is vectorized, the unrolled
loop in foo2 is not basic-block vectorized because basic-block vectorization
runs into the very same dependence issue.
Does LLVM do a runtime alias check here? For foo1 GCC adds a runtime alias
check
(BB vectorization cannot version for aliasing).
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations
