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archived-llvm/test/Transforms/InstCombine
David Bolvansky e35805b819 [InstCombine] Fold select (icmp sgt x, -1), lshr (X, Y), ashr (X, Y) to ashr (X, Y))
Summary:
(select (icmp sgt x, -1), lshr (X, Y), ashr (X, Y)) -> ashr (X, Y))
(select (icmp slt x, 1), ashr (X, Y), lshr (X, Y)) -> ashr (X, Y))

Fixes PR41173

Alive proof by @lebedev.ri (thanks)
Name: PR41173
  %cmp = icmp slt i32 %x, 1
  %shr = lshr i32 %x, %y
  %shr1 = ashr i32 %x, %y
  %retval.0 = select i1 %cmp, i32 %shr1, i32 %shr
  =>
  %retval.0 = ashr i32 %x, %y

Optimization: PR41173
Done: 1
Optimization is correct!

Reviewers: lebedev.ri, spatel

Reviewed By: lebedev.ri

Subscribers: nikic, craig.topper, llvm-commits, lebedev.ri

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64285

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@365893 91177308-0d34-0410-b5e6-96231b3b80d8
2019-07-12 11:31:16 +00:00
..
2019-06-21 17:51:18 +00:00

This directory contains test cases for the instcombine transformation.  The
dated tests are actual bug tests, whereas the named tests are used to test
for features that the this pass should be capable of performing.