https://bugs.llvm.org/show_bug.cgi?id=51539
Bug ID: 51539
Summary: [X86] Possibly incorrect throughput for vpshufb/vpperm
on bdver2 model
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: llvm-...@redking.me.uk
CC: craig.top...@gmail.com, lebedev...@gmail.com,
llvm-bugs@lists.llvm.org, llvm-...@redking.me.uk,
pengfei.w...@intel.com, spatel+l...@rotateright.com
I noticed this while working on the D103695 cost model helper script, the
llvm-mca reported bdver2 throughput for codegen containing vpshufb/vpperm is
often higher than expected.
Instruction Info:
[1]: #uOps
[2]: Latency
[3]: RThroughput
[4]: MayLoad
[5]: MayStore
[6]: HasSideEffects (U)
[1] [2] [3] [4] [5] [6] Instructions:
1 3 1.50 vpshufb %xmm0, %xmm1, %xmm2
1 2 1.50 vpperm %xmm0, %xmm1, %xmm2,
%xmm3
https://llvm.godbolt.org/z/Tsc5P4zox
All the docs I can find (AMDFam15h SoG, Agner, instlatx64 etc) indicate these
are fastpath (tp = 1.0) but just on pipe1 (xbr):
https://www.amd.com/system/files/TechDocs/47414_15h_sw_opt_guide.pdf
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