[llvm-bugs] [Bug 43605] New: [X86][SSE] X86TTIImpl::getVectorInstrCost - improve extract/insert element costs

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43605

            Bug ID: 43605
           Summary: [X86][SSE] X86TTIImpl::getVectorInstrCost - improve
                    extract/insert element costs
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, spatel+llvm at rotateright.com

The costs for vector element extraction/insertion are underestimated:

- Non/Unknown immediate index cases should be considered high cost

- Vectors before SSE41 only <8 x i16> has PINSR/PEXTR support (+MOVD/MOVQ from
index=0) - the others must be shuffled+extracted or inserted+shuffled.

- Account for the subvector handling for immediates from vector elements above
the bottom xmm.

- GPR<->XMM can be pretty nasty, assuming throughput cost = 1 is an
underestimate in most cases

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