[LSR] canonicalize Prod*(1<<C) to Prod<<C
Summary:
Because LSR happens at a late stage where mul of a power of 2 is
typically canonicalized to shl, this canonicalization emits code that
can be better CSE'ed.
Test Plan:
Transforms/LoopStrengthReduce/shl.ll shows how this change makes GVN more
powerful. Fixes some existing tests due to this change.
Reviewers: sanjoy, majnemer, atrick
Reviewed By: majnemer, atrick
Subscribers: majnemer, llvm-commits
Differential Revision: http://reviews.llvm.org/D10448
llvm-svn: 240573
diff --git a/llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll b/llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll
index 092b274..466566e 100644
--- a/llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll
+++ b/llvm/test/Transforms/LoopStrengthReduce/post-inc-icmpzero.ll
@@ -6,7 +6,7 @@
; CHECK: [[r1:%[a-z0-9]+]] = sub i64 %sub.ptr.lhs.cast, %sub.ptr.rhs.cast
; CHECK: [[r2:%[a-z0-9]+]] = lshr i64 [[r1]], 1
-; CHECK: [[r3:%[a-z0-9]+]] = mul i64 [[r2]], 2
+; CHECK: [[r3:%[a-z0-9]+]] = shl i64 [[r2]], 1
; CHECK: br label %for.body
; CHECK: for.body:
; CHECK: %lsr.iv2 = phi i64 [ %lsr.iv.next, %for.body ], [ [[r3]], %for.body.lr.ph ]