[PATCH] D78271: [TLI][PowerPC] Introduce TLI query to check if MULH is cheaper than MUL + SHIFT

[Amy Kwan via Phabricator via llvm-commits]

amyk created this revision.
amyk added reviewers: PowerPC, power-llvm-team, nemanjai, stefanp.
Herald added subscribers: llvm-commits, steven.zhang, shchenz, kbarton, hiraditya.
Herald added a project: LLVM.
amyk edited the summary of this revision.
Herald added a subscriber: wuzish.

This patch introduces a TargetLowering query, `isMulhCheaperThanMulShift`.

Currently in DAG Combine, it will transform mulhs/mulhu into a 
wider multiply and a shift if the wide multiply is legal.

This TLI function is implemented on 64-bit PowerPC, as it is more desirable to  
have multiply-high over multiply + shift for words and doublewords. Having
multiply-high can also aid in further transformations that can be done.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D78271

Files:
  llvm/include/llvm/CodeGen/TargetLowering.h
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/lib/Target/PowerPC/PPCISelLowering.cpp
  llvm/lib/Target/PowerPC/PPCISelLowering.h
  llvm/test/CodeGen/PowerPC/loop-instr-form-prepare.ll
  llvm/test/CodeGen/PowerPC/machine-pre.ll
  llvm/test/CodeGen/PowerPC/ppc64-P9-mod.ll
  llvm/test/CodeGen/PowerPC/srem-vector-lkk.ll
  llvm/test/CodeGen/PowerPC/urem-vector-lkk.ll

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