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Fix a minor bug in previous checking

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Enable folding of long seteq/setne comparisons into branches and select instructions
Implement unfolded long relational comparisons against a constants a bit more efficiently

Folding comparisons changes code that looks like this:
        mov %EAX, DWORD PTR [%ESP + 4]
        mov %EDX, DWORD PTR [%ESP + 8]
        mov %ECX, %EAX
        or %ECX, %EDX
        sete %CL
        test %CL, %CL
        je .LBB2 # PC rel: F

into code that looks like this:
        mov %EAX, DWORD PTR [%ESP + 4]
        mov %EDX, DWORD PTR [%ESP + 8]
        mov %ECX, %EAX
        or %ECX, %EDX
        jne .LBB2 # PC rel: F

This speeds up 186.crafty by 6% with llc-ls.

llvm-svn: 12702
This commit is contained in:
Chris Lattner 2004-04-06 17:34:50 +00:00
parent e2d817bc26
commit 54e93df11a
1 changed files with 29 additions and 2 deletions
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31
lib/Target/X86/InstSelectSimple.cpp
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@ -756,7 +756,9 @@ static SetCondInst *canFoldSetCCIntoBranchOrSelect(Value *V) {
Instruction *User = cast<Instruction>(SCI->use_back());
if ((isa<BranchInst>(User) || isa<SelectInst>(User)) &&
SCI->getParent() == User->getParent() &&
getClassB(SCI->getOperand(0)->getType()) != cLong)
(getClassB(SCI->getOperand(0)->getType()) != cLong ||
SCI->getOpcode() == Instruction::SetEQ ||
SCI->getOpcode() == Instruction::SetNE))
return SCI;
}
return 0;
@ -846,11 +848,36 @@ unsigned ISel::EmitComparison(unsigned OpNum, Value *Op0, Value *Op1,
unsigned HiTmp = Op0r+1;
if (HiCst != 0) {
HiTmp = makeAnotherReg(Type::IntTy);
BuildMI(*MBB, IP, X86::XOR32rr, 2,HiTmp).addReg(Op0r+1).addImm(HiCst);
BuildMI(*MBB, IP, X86::XOR32ri, 2,HiTmp).addReg(Op0r+1).addImm(HiCst);
}
unsigned FinalTmp = makeAnotherReg(Type::IntTy);
BuildMI(*MBB, IP, X86::OR32rr, 2, FinalTmp).addReg(LoTmp).addReg(HiTmp);
return OpNum;
} else {
// Emit a sequence of code which compares the high and low parts once
// each, then uses a conditional move to handle the overflow case. For
// example, a setlt for long would generate code like this:
//
// AL = lo(op1) < lo(op2) // Signedness depends on operands
// BL = hi(op1) < hi(op2) // Always unsigned comparison
// dest = hi(op1) == hi(op2) ? AL : BL;
//
// FIXME: This would be much better if we had hierarchical register
// classes! Until then, hardcode registers so that we can deal with
// their aliases (because we don't have conditional byte moves).
//
BuildMI(*MBB, IP, X86::CMP32ri, 2).addReg(Op0r).addImm(LowCst);
BuildMI(*MBB, IP, SetCCOpcodeTab[0][OpNum], 0, X86::AL);
BuildMI(*MBB, IP, X86::CMP32ri, 2).addReg(Op0r+1).addImm(HiCst);
BuildMI(*MBB, IP, SetCCOpcodeTab[CompTy->isSigned()][OpNum], 0,X86::BL);
BuildMI(*MBB, IP, X86::IMPLICIT_DEF, 0, X86::BH);
BuildMI(*MBB, IP, X86::IMPLICIT_DEF, 0, X86::AH);
BuildMI(*MBB, IP, X86::CMOVE16rr, 2, X86::BX).addReg(X86::BX)
.addReg(X86::AX);
// NOTE: visitSetCondInst knows that the value is dumped into the BL
// register at this point for long values...
return OpNum;
}
}
}