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Implement memset -> rep stos*

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19467 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-01-11 06:14:36 +00:00
parent 795069dd38
commit 989de030c4
1 changed files with 64 additions and 3 deletions
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67
lib/Target/X86/X86ISelPattern.cpp
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@ -50,7 +50,6 @@ namespace {
computeRegisterProperties();
setOperationUnsupported(ISD::MEMSET, MVT::Other);
setOperationUnsupported(ISD::MEMCPY, MVT::Other);
setOperationUnsupported(ISD::MEMMOVE, MVT::Other);
@ -1858,9 +1857,11 @@ void ISel::Select(SDOperand N) {
if (/*!N->hasOneUse() &&*/ !LoweredTokens.insert(N).second)
return; // Already selected.
switch (N.getOpcode()) {
SDNode *Node = N.Val;
switch (Node->getOpcode()) {
default:
N.Val->dump(); std::cerr << "\n";
Node->dump(); std::cerr << "\n";
assert(0 && "Node not handled yet!");
case ISD::EntryToken: return; // Noop
case ISD::CopyToReg:
@ -2027,6 +2028,66 @@ void ISel::Select(SDOperand N) {
X86::ADJCALLSTACKUP;
BuildMI(BB, Opc, 1).addImm(Tmp1);
return;
case ISD::MEMSET: {
Select(N.getOperand(0)); // Select the chain.
unsigned Align =
(unsigned)cast<ConstantSDNode>(Node->getOperand(4))->getValue();
if (Align == 0) Align = 1;
// Turn the byte code into # iterations
unsigned CountReg;
unsigned Opcode;
if (ConstantSDNode *ValC = dyn_cast<ConstantSDNode>(Node->getOperand(2))) {
unsigned Val = ValC->getValue() & 255;
// If the value is a constant, then we can potentially use larger sets.
switch (Align & 3) {
case 2: // WORD aligned
CountReg = MakeReg(MVT::i32);
if (ConstantSDNode *I = dyn_cast<ConstantSDNode>(Node->getOperand(3))) {
BuildMI(BB, X86::MOV32ri, 1, CountReg).addImm(I->getValue()/2);
} else {
unsigned ByteReg = SelectExpr(Node->getOperand(3));
BuildMI(BB, X86::SHR32ri, 2, CountReg).addReg(ByteReg).addImm(1);
}
BuildMI(BB, X86::MOV16ri, 1, X86::AX).addImm((Val << 8) | Val);
Opcode = X86::REP_STOSW;
break;
case 0: // DWORD aligned
CountReg = MakeReg(MVT::i32);
if (ConstantSDNode *I = dyn_cast<ConstantSDNode>(Node->getOperand(3))) {
BuildMI(BB, X86::MOV32ri, 1, CountReg).addImm(I->getValue()/4);
} else {
unsigned ByteReg = SelectExpr(Node->getOperand(3));
BuildMI(BB, X86::SHR32ri, 2, CountReg).addReg(ByteReg).addImm(2);
}
Val = (Val << 8) | Val;
BuildMI(BB, X86::MOV32ri, 1, X86::EAX).addImm((Val << 16) | Val);
Opcode = X86::REP_STOSD;
break;
default: // BYTE aligned
CountReg = SelectExpr(Node->getOperand(3));
BuildMI(BB, X86::MOV8ri, 1, X86::AL).addImm(Val);
Opcode = X86::REP_STOSB;
break;
}
} else {
// If it's not a constant value we are storing, just fall back. We could
// try to be clever to form 16 bit and 32 bit values, but we don't yet.
unsigned ValReg = SelectExpr(Node->getOperand(2));
BuildMI(BB, X86::MOV8rr, 1, X86::AL).addReg(ValReg);
CountReg = SelectExpr(Node->getOperand(3));
Opcode = X86::REP_STOSB;
}
// No matter what the alignment is, we put the source in ESI, the
// destination in EDI, and the count in ECX.
unsigned TmpReg1 = SelectExpr(Node->getOperand(1));
BuildMI(BB, X86::MOV32rr, 1, X86::ECX).addReg(CountReg);
BuildMI(BB, X86::MOV32rr, 1, X86::EDI).addReg(TmpReg1);
BuildMI(BB, Opcode, 0);
return;
}
}
assert(0 && "Should not be reached!");
}