https://bugs.llvm.org/show_bug.cgi?id=46249
Bug ID: 46249
Summary: [X86] VPSHUFD and VPERMQ with immediates combined into
VPERMD with variable mask
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: craig.top...@gmail.com
CC: craig.top...@gmail.com, llvm-bugs@lists.llvm.org,
llvm-...@redking.me.uk, spatel+l...@rotateright.com
As noted here https://twitter.com/damageboy/status/1270266352406802432
We combined
t45: v16i32 = vector_shuffle<3,2,1,0,7,6,5,4,11,10,9,8,15,14,13,12> t44,
undef:v16i32
t46: v16i32 = vector_shuffle<8,9,10,11,12,13,14,15,0,1,2,3,4,5,6,7> t45,
undef:v16i32
into
t258: v16i32 = vector_shuffle<11,10,9,8,15,14,13,12,3,2,1,0,7,6,5,4>
Which then required vpermd.
This happened before lowering and lowering doesn't know to recreate the two
shuffles. Simon, would hasFastVariableShuffle() also have created a VPERMD if
lowering had managed to make 2 immediate shuffles?
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