[DAGCombiner] PCMP* sets its result to all ones or zeros so we can AND with the
shifted mask rather than masking and shifting separately.
The patch adds this transformation to the DAGCombiner:
(shl (and (setcc:i8v16 ...) N01C) N1C) -> (and (setcc:i8v16 ...) N01C<<N1C)
<rdar://problem/16054492>
Patch by Adam Nemet <anemet@apple.com>
llvm-svn: 201906
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index de8fbc9..76974c2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3818,6 +3818,24 @@
if (VT.isVector()) {
SDValue FoldedVOp = SimplifyVBinOp(N);
if (FoldedVOp.getNode()) return FoldedVOp;
+
+ BuildVectorSDNode *N1CV = dyn_cast<BuildVectorSDNode>(N1);
+ // If setcc produces all-one true value then:
+ // (shl (and (setcc) N01CV) N1CV) -> (and (setcc) N01CV<<N1CV)
+ if (N1CV && N1CV->isConstant() &&
+ TLI.getBooleanContents(true) ==
+ TargetLowering::ZeroOrNegativeOneBooleanContent &&
+ N0.getOpcode() == ISD::AND) {
+ SDValue N00 = N0->getOperand(0);
+ SDValue N01 = N0->getOperand(1);
+ BuildVectorSDNode *N01CV = dyn_cast<BuildVectorSDNode>(N01);
+
+ if (N01CV && N01CV->isConstant() && N00.getOpcode() == ISD::SETCC) {
+ SDValue C = DAG.FoldConstantArithmetic(ISD::SHL, VT, N01CV, N1CV);
+ if (C.getNode())
+ return DAG.getNode(ISD::AND, SDLoc(N), VT, N00, C);
+ }
+ }
}
// fold (shl c1, c2) -> c1<<c2