Don't emit a bit test if there is only one case the test can yield false. A simple SETNE is sufficient.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135126 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 66b6024..3a04ee1 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1727,7 +1727,8 @@
SDValue ShiftOp = DAG.getCopyFromReg(getControlRoot(), getCurDebugLoc(),
Reg, VT);
SDValue Cmp;
- if (CountPopulation_64(B.Mask) == 1) {
+ unsigned PopCount = CountPopulation_64(B.Mask);
+ if (PopCount == 1) {
// Testing for a single bit; just compare the shift count with what it
// would need to be to shift a 1 bit in that position.
Cmp = DAG.getSetCC(getCurDebugLoc(),
@@ -1735,6 +1736,13 @@
ShiftOp,
DAG.getConstant(CountTrailingZeros_64(B.Mask), VT),
ISD::SETEQ);
+ } else if (PopCount == BB.Range) {
+ // There is only one zero bit in the range, test for it directly.
+ Cmp = DAG.getSetCC(getCurDebugLoc(),
+ TLI.getSetCCResultType(VT),
+ ShiftOp,
+ DAG.getConstant(CountTrailingOnes_64(B.Mask), VT),
+ ISD::SETNE);
} else {
// Make desired shift
SDValue SwitchVal = DAG.getNode(ISD::SHL, getCurDebugLoc(), VT,