Reorder shuffle and binary operation.
This patch enables transformations:
BinOp(shuffle(v1), shuffle(v2)) -> shuffle(BinOp(v1, v2))
BinOp(shuffle(v1), const1) -> shuffle(BinOp, const2)
They allow to eliminate extra shuffles in some cases.
Differential Revision: http://reviews.llvm.org/D3525
llvm-svn: 208488
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index b072b4d..bd647d9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -839,6 +839,20 @@
llvm_unreachable("failed to reorder elements of vector instruction!");
}
+static void RecognizeIdentityMask(const SmallVectorImpl<int> &Mask,
+ bool &isLHSID, bool &isRHSID) {
+ isLHSID = isRHSID = true;
+
+ for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
+ if (Mask[i] < 0) continue; // Ignore undef values.
+ // Is this an identity shuffle of the LHS value?
+ isLHSID &= (Mask[i] == (int)i);
+
+ // Is this an identity shuffle of the RHS value?
+ isRHSID &= (Mask[i]-e == i);
+ }
+}
+
Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
Value *LHS = SVI.getOperand(0);
Value *RHS = SVI.getOperand(1);
@@ -902,16 +916,8 @@
if (VWidth == LHSWidth) {
// Analyze the shuffle, are the LHS or RHS and identity shuffles?
- bool isLHSID = true, isRHSID = true;
-
- for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
- if (Mask[i] < 0) continue; // Ignore undef values.
- // Is this an identity shuffle of the LHS value?
- isLHSID &= (Mask[i] == (int)i);
-
- // Is this an identity shuffle of the RHS value?
- isRHSID &= (Mask[i]-e == i);
- }
+ bool isLHSID, isRHSID;
+ RecognizeIdentityMask(Mask, isLHSID, isRHSID);
// Eliminate identity shuffles.
if (isLHSID) return ReplaceInstUsesWith(SVI, LHS);
@@ -1106,5 +1112,14 @@
return new ShuffleVectorInst(newLHS, newRHS, ConstantVector::get(Elts));
}
+ // If the result mask is an identity, replace uses of this instruction with
+ // corresponding argument.
+ if (VWidth == LHSWidth) {
+ bool isLHSID, isRHSID;
+ RecognizeIdentityMask(newMask, isLHSID, isRHSID);
+ if (isLHSID) return ReplaceInstUsesWith(SVI, newLHS);
+ if (isRHSID) return ReplaceInstUsesWith(SVI, newRHS);
+ }
+
return MadeChange ? &SVI : nullptr;
}