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Improve code generated for integer multiplications by 2,3,5,9

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llvm-svn: 13342
This commit is contained in:
Chris Lattner 2004-05-04 15:47:14 +00:00
parent 7896144611
commit cb9a614ea4
1 changed files with 16 additions and 2 deletions
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18
lib/Target/X86/InstSelectSimple.cpp
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@ -2196,15 +2196,29 @@ void ISel::doMultiplyConst(MachineBasicBlock *MBB,
unsigned op0Reg, unsigned ConstRHS) {
static const unsigned MOVrrTab[] = {X86::MOV8rr, X86::MOV16rr, X86::MOV32rr};
static const unsigned MOVriTab[] = {X86::MOV8ri, X86::MOV16ri, X86::MOV32ri};
static const unsigned ADDrrTab[] = {X86::ADD8rr, X86::ADD16rr, X86::ADD32rr};
unsigned Class = getClass(DestTy);
if (ConstRHS == 0) {
// Handle special cases here.
switch (ConstRHS) {
case 0:
BuildMI(*MBB, IP, MOVriTab[Class], 1, DestReg).addImm(0);
return;
} else if (ConstRHS == 1) {
case 1:
BuildMI(*MBB, IP, MOVrrTab[Class], 1, DestReg).addReg(op0Reg);
return;
case 2:
BuildMI(*MBB, IP, ADDrrTab[Class], 1,DestReg).addReg(op0Reg).addReg(op0Reg);
return;
case 3:
case 5:
case 9:
if (Class == cInt) {
addFullAddress(BuildMI(*MBB, IP, X86::LEA32r, 5, DestReg),
op0Reg, ConstRHS-1, op0Reg, 0);
return;
}
}
// If the element size is exactly a power of 2, use a shift to get it.