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Use xor to clear a register.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28667 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2006-06-02 21:20:34 +00:00
parent 94b1453278
commit aede9b9598
1 changed files with 4 additions and 6 deletions
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10
lib/Target/X86/X86ISelDAGToDAG.cpp
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@ -744,17 +744,17 @@ void X86DAGToDAGISel::Select(SDOperand &Result, SDOperand N) {
default: assert(0 && "Unsupported VT!"); default: assert(0 && "Unsupported VT!");
case MVT::i8: case MVT::i8:
LoReg = X86::AL; HiReg = X86::AH; LoReg = X86::AL; HiReg = X86::AH;
ClrOpcode = X86::MOV8ri; ClrOpcode = X86::MOV8r0;
SExtOpcode = X86::CBW; SExtOpcode = X86::CBW;
break; break;
case MVT::i16: case MVT::i16:
LoReg = X86::AX; HiReg = X86::DX; LoReg = X86::AX; HiReg = X86::DX;
ClrOpcode = X86::MOV16ri; ClrOpcode = X86::MOV16r0;
SExtOpcode = X86::CWD; SExtOpcode = X86::CWD;
break; break;
case MVT::i32: case MVT::i32:
LoReg = X86::EAX; HiReg = X86::EDX; LoReg = X86::EAX; HiReg = X86::EDX;
ClrOpcode = X86::MOV32ri; ClrOpcode = X86::MOV32r0;
SExtOpcode = X86::CDQ; SExtOpcode = X86::CDQ;
break; break;
} }
@ -783,9 +783,7 @@ void X86DAGToDAGISel::Select(SDOperand &Result, SDOperand N) {
SDOperand(CurDAG->getTargetNode(SExtOpcode, MVT::Flag, InFlag), 0); SDOperand(CurDAG->getTargetNode(SExtOpcode, MVT::Flag, InFlag), 0);
} else { } else {
// Zero out the high part, effectively zero extending the input. // Zero out the high part, effectively zero extending the input.
SDOperand ClrNode = SDOperand ClrNode = SDOperand(CurDAG->getTargetNode(ClrOpcode, NVT), 0);
SDOperand(CurDAG->getTargetNode(ClrOpcode, NVT,
CurDAG->getTargetConstant(0, NVT)), 0);
Chain = CurDAG->getCopyToReg(Chain, CurDAG->getRegister(HiReg, NVT), Chain = CurDAG->getCopyToReg(Chain, CurDAG->getRegister(HiReg, NVT),
ClrNode, InFlag); ClrNode, InFlag);
InFlag = Chain.getValue(1); InFlag = Chain.getValue(1);