[all-commits] [llvm/llvm-project] 4d83ab: [DAGCombine] Adding a hook to improve the precisio...

[QingShan Zhang via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 4d83aba4228ecb7dfefaf10a36a35f7299467819
      https://github.com/llvm/llvm-project/commit/4d83aba4228ecb7dfefaf10a36a35f7299467819
  Author: QingShan Zhang <qshanz at cn.ibm.com>
  Date:   2020-11-27 (Fri, 27 Nov 2020)

  Changed paths:
    M llvm/include/llvm/CodeGen/TargetLowering.h
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/lib/Target/PowerPC/PPCISelLowering.cpp
    M llvm/lib/Target/PowerPC/PPCISelLowering.h
    M llvm/lib/Target/PowerPC/PPCInstrInfo.td
    M llvm/lib/Target/PowerPC/PPCInstrVSX.td
    M llvm/test/CodeGen/PowerPC/fma-mutate.ll
    M llvm/test/CodeGen/PowerPC/recipest.ll

  Log Message:
  -----------
  [DAGCombine] Adding a hook to improve the precision of fsqrt if the input is denormal

For now, we will hardcode the result as 0.0 if the input is denormal or 0. That will
have the impact the precision. As the fsqrt added belong to the cold path of the
cmp+branch, it won't impact the performance for normal inputs for PowerPC, but improve
the precision if the input is denormal.

Reviewed By: Spatel

Differential Revision: https://reviews.llvm.org/D80974