[InstCombine] canonicalize another raw IR rotate pattern to funnel shift

This is matching the equivalent of the DAG expansion, 
so it should never end up with worse perf than the 
original code even if the target doesn't have a rotate
instruction.

llvm-svn: 350672

1 files changed, 2 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index ebbe2afe3ec..faf58a08976 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -1557,8 +1557,7 @@ static Instruction *factorizeMinMaxTree(SelectPatternFlavor SPF, Value *LHS,
 /// funnel shift intrinsic. Example:
 /// rotl32(a, b) --> (b == 0 ? a : ((a >> (32 - b)) | (a << b)))
 ///              --> call llvm.fshl.i32(a, a, b)
-static Instruction *foldSelectRotate(SelectInst &Sel,
-                                     InstCombiner::BuilderTy &Builder) {
+static Instruction *foldSelectRotate(SelectInst &Sel) {
   // The false value of the select must be a rotate of the true value.
   Value *Or0, *Or1;
   if (!match(Sel.getFalseValue(), m_OneUse(m_Or(m_Value(Or0), m_Value(Or1)))))
@@ -2047,7 +2046,7 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
   if (Instruction *Select = foldSelectBinOpIdentity(SI, TLI))
     return Select;
 
-  if (Instruction *Rot = foldSelectRotate(SI, Builder))
+  if (Instruction *Rot = foldSelectRotate(SI))
     return Rot;
 
   return nullptr;