On 11/23/2021 11:34 AM, Navid Rahimi via Gcc-patches wrote:
Hi GCC community,
I wanted you take a quick look at this patch to solve this bug [1]. This is the
code example for the optimization [2] which does include a link to proof of
each different optimization.
I think it should be possible to use simpler approach than what Andrew has used
here [3].
P.S. Tested and verified on Linux x86_64.
1) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101808
2) https://compiler-explorer.com/z/Gc448eE3z
3) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101808#c1
Don't those match.pd patterns make things worse? We're taking a single
expression evaluation (the conditional) and turning it into two logicals
AFAICT.
For the !x expression, obviously if x is a constant, then we can
compute that at compile time and we're going from a single conditional
to a single logical which is probably a win, but that's not the case
with this patch AFAICT.
jeff
