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Implement negation of longs efficiently. For this testcase:

Browse Source 
long %test(long %X) {
        %Y = sub long 0, %X
        ret long %Y
}

We used to generate:

test:
        sub %ESP, 4
        mov DWORD PTR [%ESP], %ESI
        mov %ECX, DWORD PTR [%ESP + 8]
        mov %ESI, DWORD PTR [%ESP + 12]
        mov %EAX, 0
        mov %EDX, 0
        sub %EAX, %ECX
        sbb %EDX, %ESI
        mov %ESI, DWORD PTR [%ESP]
        add %ESP, 4
        ret

Now we generate:

test:
        mov %EAX, DWORD PTR [%ESP + 4]
        mov %EDX, DWORD PTR [%ESP + 8]
        neg %EAX
        adc %EDX, 0
        neg %EDX
        ret


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12681 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-04-06 01:48:06 +00:00
parent 502e36c3c9
commit edd5e4957a
2 changed files with 22 additions and 4 deletions
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13
lib/Target/X86/InstSelectSimple.cpp
View File

@ -1690,14 +1690,23 @@ void ISel::emitSimpleBinaryOperation(MachineBasicBlock *MBB,
unsigned Class = getClassB(Op0->getType());
// sub 0, X -> neg X
if (OperatorClass == 1 && Class != cLong)
if (OperatorClass == 1)
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0)) {
if (CI->isNullValue()) {
unsigned op1Reg = getReg(Op1, MBB, IP);
static unsigned const NEGTab[] = {
X86::NEG8r, X86::NEG16r, X86::NEG32r
X86::NEG8r, X86::NEG16r, X86::NEG32r, 0, X86::NEG32r
};
BuildMI(*MBB, IP, NEGTab[Class], 1, DestReg).addReg(op1Reg);
if (Class == cLong) {
// We just emitted: Dl = neg Sl
// Now emit : T = addc Sh, 0
// : Dh = neg T
unsigned T = makeAnotherReg(Type::IntTy);
BuildMI(*MBB, IP, X86::ADC32ri, 2, T).addReg(op1Reg+1).addImm(0);
BuildMI(*MBB, IP, X86::NEG32r, 1, DestReg+1).addReg(T);
}
return;
}
} else if (ConstantFP *CFP = dyn_cast<ConstantFP>(Op0))

13
lib/Target/X86/X86ISelSimple.cpp
View File

@ -1690,14 +1690,23 @@ void ISel::emitSimpleBinaryOperation(MachineBasicBlock *MBB,
unsigned Class = getClassB(Op0->getType());
// sub 0, X -> neg X
if (OperatorClass == 1 && Class != cLong)
if (OperatorClass == 1)
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0)) {
if (CI->isNullValue()) {
unsigned op1Reg = getReg(Op1, MBB, IP);
static unsigned const NEGTab[] = {
X86::NEG8r, X86::NEG16r, X86::NEG32r
X86::NEG8r, X86::NEG16r, X86::NEG32r, 0, X86::NEG32r
};
BuildMI(*MBB, IP, NEGTab[Class], 1, DestReg).addReg(op1Reg);
if (Class == cLong) {
// We just emitted: Dl = neg Sl
// Now emit : T = addc Sh, 0
// : Dh = neg T
unsigned T = makeAnotherReg(Type::IntTy);
BuildMI(*MBB, IP, X86::ADC32ri, 2, T).addReg(op1Reg+1).addImm(0);
BuildMI(*MBB, IP, X86::NEG32r, 1, DestReg+1).addReg(T);
}
return;
}
} else if (ConstantFP *CFP = dyn_cast<ConstantFP>(Op0))