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Emit more efficient 64-bit operations when the RHS is a constant, and one

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of the words of the constant is zeros.  For example:
  Y = and long X, 1234

now generates:
  Yl = and Xl, 1234
  Yh = 0

instead of:
  Yl = and Xl, 1234
  Yh = and Xh, 0

llvm-svn: 12685
This commit is contained in:
Chris Lattner 2004-04-06 03:15:53 +00:00
parent bdbedf9523
commit 2738d6d4a4
1 changed files with 41 additions and 5 deletions
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46
lib/Target/X86/InstSelectSimple.cpp
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@ -1767,18 +1767,54 @@ void ISel::emitSimpleBinaryOperation(MachineBasicBlock *MBB,
};
unsigned Opcode = OpcodeTab[OperatorClass][Class];
unsigned Op1l = cast<ConstantInt>(Op1C)->getRawValue();
uint64_t Op1v = cast<ConstantInt>(Op1C)->getRawValue();
BuildMI(*MBB, IP, Opcode, 2, DestReg).addReg(Op0r).addImm(Op1v &0xFFFFFFFF);
if (Class != cLong) {
BuildMI(*MBB, IP, Opcode, 2, DestReg).addReg(Op0r).addImm(Op1l);
return;
} else {
// If this is a long value and the high or low bits have a special
// property, emit some special cases.
unsigned Op1h = cast<ConstantInt>(Op1C)->getRawValue() >> 32LL;
if (Class == cLong) {
// If the constant is zero in the low 32-bits, just copy the low part
// across and apply the normal 32-bit operation to the high parts. There
// will be no carry or borrow into the top.
if (Op1l == 0) {
if (OperatorClass != 2) // All but and...
BuildMI(*MBB, IP, X86::MOV32rr, 1, DestReg).addReg(Op0r);
else
BuildMI(*MBB, IP, X86::MOV32ri, 1, DestReg).addImm(0);
BuildMI(*MBB, IP, OpcodeTab[OperatorClass][cLong], 2, DestReg+1)
.addReg(Op0r+1).addImm(Op1h);
return;
}
// If this is a logical operation and the top 32-bits are zero, just
// operate on the lower 32.
if (Op1h == 0 && OperatorClass > 1) {
BuildMI(*MBB, IP, OpcodeTab[OperatorClass][cLong], 2, DestReg)
.addReg(Op0r).addImm(Op1l);
if (OperatorClass != 2) // All but and
BuildMI(*MBB, IP, X86::MOV32rr, 1, DestReg+1).addReg(Op0r+1);
else
BuildMI(*MBB, IP, X86::MOV32ri, 1, DestReg+1).addImm(0);
return;
}
// TODO: We could handle lots of other special cases here, such as AND'ing
// with 0xFFFFFFFF00000000 -> noop, etc.
// Otherwise, code generate the full operation with a constant.
static const unsigned TopTab[] = {
X86::ADC32ri, X86::SBB32ri, X86::AND32ri, X86::OR32ri, X86::XOR32ri
};
BuildMI(*MBB, IP, Opcode, 2, DestReg).addReg(Op0r).addImm(Op1l);
BuildMI(*MBB, IP, TopTab[OperatorClass], 2, DestReg+1)
.addReg(Op0r+1).addImm(uint64_t(Op1v) >> 32);
.addReg(Op0r+1).addImm(Op1h);
return;
}
return;
}
// Finally, handle the general case now.