[PATCH] D20931: [X86] Reduce the width of multiplification when its operands are extended from i8 or i16

[Wei Mi via llvm-commits]

wmi updated this revision to Diff 59745.
wmi added a comment.

Addressed Eli and Michael's comments.

A major change is: The previous way to choose shrinking modes by only looking at sext and zext is incorrect. I should analyze and use the value ranges of mul operands to determine which shrinking mode should be chosen. Different shrinking modes and their allowed value ranges are described in the comment of reduceVMULWidth.


Repository:
  rL LLVM

http://reviews.llvm.org/D20931

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/shrink_vmul.ll

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