[llvm-commits] CVS: llvm/lib/Target/X86/InstSelectSimple.cpp
Chris Lattner
lattner at cs.uiuc.edu
Mon Apr 5 20:49:01 PDT 2004
Changes in directory llvm/lib/Target/X86:
InstSelectSimple.cpp updated: 1.206 -> 1.207
---
Log message:
Implement negation of longs efficiently. For this testcase:
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
---
Diffs of the changes: (+11 -2)
Index: llvm/lib/Target/X86/InstSelectSimple.cpp
diff -u llvm/lib/Target/X86/InstSelectSimple.cpp:1.206 llvm/lib/Target/X86/InstSelectSimple.cpp:1.207
--- llvm/lib/Target/X86/InstSelectSimple.cpp:1.206 Mon Apr 5 20:25:33 2004
+++ llvm/lib/Target/X86/InstSelectSimple.cpp Mon Apr 5 20:48:06 2004
@@ -1690,14 +1690,23 @@
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))
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