Reapply "[ARM] Combine CMOV into BFI where possible"
Added fixes for stage2 failures: CMOV is not commutable; commuting the operands results in the condition being flipped! d'oh!
Original commit message:
If we have a CMOV, OR and AND combination such as:
if (x & CN)
y |= CM;
And:
* CN is a single bit;
* All bits covered by CM are known zero in y;
Then we can convert this to a sequence of BFI instructions. This will always be a win if CM is a single bit, will always be no worse than the TST & OR sequence if CM is two bits, and for thumb will be no worse if CM is three bits (due to the extra IT instruction).
llvm-svn: 252606
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.h b/llvm/lib/Target/ARM/ARMISelLowering.h
index df4b655..534f92b 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.h
+++ b/llvm/lib/Target/ARM/ARMISelLowering.h
@@ -260,6 +260,7 @@
SDNode *Node) const override;
SDValue PerformCMOVCombine(SDNode *N, SelectionDAG &DAG) const;
+ SDValue PerformCMOVToBFICombine(SDNode *N, SelectionDAG &DAG) const;
SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;
bool isDesirableToTransformToIntegerOp(unsigned Opc, EVT VT) const override;