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Generate better code by being far less clever when it comes to the select instruction. Don't create overlapping register lifetimes 

llvm-svn: 16580
This commit is contained in:
Nate Begeman 2004-09-29 05:00:31 +00:00
parent c44da15813
commit 2f1d0ae95e
1 changed files with 17 additions and 7 deletions
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24
llvm/lib/Target/PowerPC/PPC32ISelSimple.cpp
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@ -1296,7 +1296,6 @@ void PPC32ISel::emitSelectOperation(MachineBasicBlock *MBB,
BuildMI(*MBB, IP, PPC::CMPWI, 2, PPC::CR0).addReg(CondReg).addSImm(0);
Opcode = getPPCOpcodeForSetCCNumber(Instruction::SetNE);
}
unsigned TrueValue = getReg(TrueVal, BB, BB->end());
MachineBasicBlock *thisMBB = BB;
const BasicBlock *LLVM_BB = BB->getBasicBlock();
@ -1306,22 +1305,33 @@ void PPC32ISel::emitSelectOperation(MachineBasicBlock *MBB,
// thisMBB:
// ...
// cmpTY cr0, r1, r2
// %TrueValue = ...
// bCC sinkMBB
// bCC copy1MBB
// fallthrough --> copy0MBB
MachineBasicBlock *copy0MBB = new MachineBasicBlock(LLVM_BB);
MachineBasicBlock *copy1MBB = new MachineBasicBlock(LLVM_BB);
MachineBasicBlock *sinkMBB = new MachineBasicBlock(LLVM_BB);
BuildMI(BB, Opcode, 2).addReg(PPC::CR0).addMBB(sinkMBB);
BuildMI(BB, Opcode, 2).addReg(PPC::CR0).addMBB(copy1MBB);
F->getBasicBlockList().insert(It, copy0MBB);
F->getBasicBlockList().insert(It, copy1MBB);
F->getBasicBlockList().insert(It, sinkMBB);
// Update machine-CFG edges
BB->addSuccessor(copy0MBB);
BB->addSuccessor(sinkMBB);
BB->addSuccessor(copy1MBB);
// copy0MBB:
// %FalseValue = ...
// fallthrough
// b sinkMBB
BB = copy0MBB;
unsigned FalseValue = getReg(FalseVal, BB, BB->begin());
BuildMI(BB, PPC::B, 1).addMBB(sinkMBB);
// Update machine-CFG edges
BB->addSuccessor(sinkMBB);
// copy1MBB:
// %TrueValue = ...
// fallthrough
BB = copy1MBB;
unsigned TrueValue = getReg(TrueVal, BB, BB->begin());
// Update machine-CFG edges
BB->addSuccessor(sinkMBB);
@ -1330,7 +1340,7 @@ void PPC32ISel::emitSelectOperation(MachineBasicBlock *MBB,
// ...
BB = sinkMBB;
BuildMI(BB, PPC::PHI, 4, DestReg).addReg(FalseValue)
.addMBB(copy0MBB).addReg(TrueValue).addMBB(thisMBB);
.addMBB(copy0MBB).addReg(TrueValue).addMBB(copy1MBB);
// For a register pair representing a long value, define the second reg
// FIXME: Can this really be correct for selecting longs?