Implement ARMBaseInstrInfo::commuteInstruction() for MOVCCr.
A MOVCCr instruction can be commuted by inverting the condition. This
can help reduce register pressure and remove unnecessary copies in some
cases.
<rdar://problem/11182914>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154033 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index 56cd6e5..c6280f8 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -1500,6 +1500,29 @@
llvm_unreachable("Unknown unconditional branch opcode!");
}
+/// commuteInstruction - Handle commutable instructions.
+MachineInstr *
+ARMBaseInstrInfo::commuteInstruction(MachineInstr *MI, bool NewMI) const {
+ switch (MI->getOpcode()) {
+ case ARM::MOVCCr:
+ case ARM::t2MOVCCr: {
+ // MOVCC can be commuted by inverting the condition.
+ unsigned PredReg = 0;
+ ARMCC::CondCodes CC = getInstrPredicate(MI, PredReg);
+ // MOVCC AL can't be inverted. Shouldn't happen.
+ if (CC == ARMCC::AL || PredReg != ARM::CPSR)
+ return NULL;
+ MI = TargetInstrInfoImpl::commuteInstruction(MI, NewMI);
+ if (!MI)
+ return NULL;
+ // After swapping the MOVCC operands, also invert the condition.
+ MI->getOperand(MI->findFirstPredOperandIdx())
+ .setImm(ARMCC::getOppositeCondition(CC));
+ return MI;
+ }
+ }
+ return TargetInstrInfoImpl::commuteInstruction(MI, NewMI);
+}
/// Map pseudo instructions that imply an 'S' bit onto real opcodes. Whether the
/// instruction is encoded with an 'S' bit is determined by the optional CPSR