https://bugs.llvm.org/show_bug.cgi?id=48816
Bug ID: 48816
Summary: Failure to simplify trunc(abs(sext(x))) -> abs(x)
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: llvm-...@redking.me.uk
CC: lebedev...@gmail.com, llvm-bugs@lists.llvm.org,
nikita....@gmail.com, nunoplo...@sapo.pt,
spatel+l...@rotateright.com
Noticed while investigating the quality of vectorization for:
https://github.com/WojciechMula/toys/blob/master/autovectorization-tests/transform_abs.cpp
(see http://0x80.pl/notesen/2021-01-18-autovectorization-gcc-clang.html for the
full list).
Due to promotions in the c code, for the "transform_abs_epi8" pattern we end up
with this:
%20 = load <32 x i8>, <32 x i8>* %19
%21 = sext <32 x i8> %20 to <32 x i32>
%22 = call <32 x i32> @llvm.abs.v32i32(<32 x i32> %21, i1 true)
%23 = trunc <32 x i32> %22 to <32 x i8>
https://gcc.godbolt.org/z/qoYv6s
AFAICT we should be able to remove the sext/trunc and use a v32i8 abs as long
as we clear the "is_int_min_poison" flag:
https://alive2.llvm.org/ce/z/Fvwhka
%23 = call <32 x i8> @llvm.abs.v32i8(<32 x i8> %20, i1 false)
What are the implications of clearing the poison flag as part of such a fold?
--
You are receiving this mail because:
You are on the CC list for the bug._______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
