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

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.h b/llvm/lib/Target/ARM/ARMISelLowering.h
index df4b6553ab5..534f92b941c 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.h
+++ b/llvm/lib/Target/ARM/ARMISelLowering.h
@@ -260,6 +260,7 @@ namespace llvm {
                                        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;