[PATCH] D38668: [X86] Fix for 20871

[Riyaz V Puthiyapurayil via Phabricator via llvm-commits]

RVP added a comment.

For the reduced test case in https://bugs.llvm.org/show_bug.cgi?id=20871

`opt -licm -instcombine -indvars reduce.bc | llvm-dis | grep i65

  %18 = zext i64 %17 to i65
  %19 = zext i64 %9 to i65
  %20 = mul i65 %18, %19
  %21 = lshr i65 %20, 1
  %22 = trunc i65 %21 to i64`


https://reviews.llvm.org/D38668