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Fix a FIXME: Select instructions on longs were miscompiled. 

While we're at it, improve codegen of select instructions.  For this
testcase:

int %test(bool %C, int %A, int %B) {
  %D = select bool %C, int %A, int %B
  ret int %D
}

We used to generate this code:

_test:
        cmpwi cr0, r3, 0
        bne .LBB_test_2 ;
.LBB_test_1:    ;
        b .LBB_test_3   ;
.LBB_test_2:    ;
        or r5, r4, r4
.LBB_test_3:    ;
        or r3, r5, r5
        blr

Now we emit:

_test:
        cmpwi cr0, r3, 0
        bne .LBB_test_2 ;
.LBB_test_1:    ;
        or r4, r5, r5
.LBB_test_2:    ;
        or r3, r4, r4
        blr

-Chris

llvm-svn: 19214
This commit is contained in:
Chris Lattner 2005-01-01 16:10:12 +00:00
parent 78394258ae
commit 83df5d25b7
1 changed files with 9 additions and 19 deletions
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28
llvm/lib/Target/PowerPC/PPC32ISelSimple.cpp
View File

@ -1429,34 +1429,25 @@ void PPC32ISel::emitSelectOperation(MachineBasicBlock *MBB,
// thisMBB:
// ...
// TrueVal = ...
// cmpTY cr0, r1, r2
// 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(copy1MBB);
unsigned TrueValue = getReg(TrueVal, BB, BB->begin());
BuildMI(BB, Opcode, 2).addReg(PPC::CR0).addMBB(sinkMBB);
F->getBasicBlockList().insert(It, copy0MBB);
F->getBasicBlockList().insert(It, copy1MBB);
F->getBasicBlockList().insert(It, sinkMBB);
// Update machine-CFG edges
BB->addSuccessor(copy0MBB);
BB->addSuccessor(copy1MBB);
BB->addSuccessor(sinkMBB);
// copy0MBB:
// %FalseValue = ...
// b sinkMBB
// # fallthrough to 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);
@ -1465,13 +1456,12 @@ void PPC32ISel::emitSelectOperation(MachineBasicBlock *MBB,
// ...
BB = sinkMBB;
BuildMI(BB, PPC::PHI, 4, DestReg).addReg(FalseValue)
.addMBB(copy0MBB).addReg(TrueValue).addMBB(copy1MBB);
.addMBB(copy0MBB).addReg(TrueValue).addMBB(thisMBB);
// For a register pair representing a long value, define the second reg
// FIXME: Can this really be correct for selecting longs?
// For a register pair representing a long value, define the top part.
if (getClassB(TrueVal->getType()) == cLong)
BuildMI(BB, PPC::LI, 1, DestReg+1).addImm(0);
return;
BuildMI(BB, PPC::PHI, 4, DestReg+1).addReg(FalseValue+1)
.addMBB(copy0MBB).addReg(TrueValue+1).addMBB(thisMBB);
}