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Fold setcc instructions into selects.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19438 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-01-10 22:10:13 +00:00
parent 57fbfb5879
commit 24aad1b0c1
1 changed files with 116 additions and 18 deletions
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134
lib/Target/X86/X86ISelPattern.cpp
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@ -1,5 +1,5 @@
//===-- X86ISelPattern.cpp - A pattern matching inst selector for X86 -----===//
//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
@ -348,6 +348,8 @@ namespace {
void EmitCMP(SDOperand LHS, SDOperand RHS);
bool EmitBranchCC(MachineBasicBlock *Dest, SDOperand Cond);
void EmitSelectCC(SDOperand Cond, MVT::ValueType SVT,
unsigned RTrue, unsigned RFalse, unsigned RDest);
unsigned SelectExpr(SDOperand N);
bool SelectAddress(SDOperand N, X86AddressMode &AM);
void Select(SDOperand N);
@ -622,6 +624,116 @@ bool ISel::EmitBranchCC(MachineBasicBlock *Dest, SDOperand Cond) {
return false;
}
/// EmitSelectCC - Emit code into BB that performs a select operation between
/// the two registers RTrue and RFalse, generating a result into RDest. Return
/// true if the fold cannot be performed.
///
void ISel::EmitSelectCC(SDOperand Cond, MVT::ValueType SVT,
unsigned RTrue, unsigned RFalse, unsigned RDest) {
enum Condition {
EQ, NE, LT, LE, GT, GE, B, BE, A, AE, P, NP,
NOT_SET
} CondCode = NOT_SET;
static const unsigned CMOVTAB16[] = {
X86::CMOVE16rr, X86::CMOVNE16rr, X86::CMOVL16rr, X86::CMOVLE16rr,
X86::CMOVG16rr, X86::CMOVGE16rr, X86::CMOVB16rr, X86::CMOVBE16rr,
X86::CMOVA16rr, X86::CMOVAE16rr, X86::CMOVP16rr, X86::CMOVNP16rr,
};
static const unsigned CMOVTAB32[] = {
X86::CMOVE32rr, X86::CMOVNE32rr, X86::CMOVL32rr, X86::CMOVLE32rr,
X86::CMOVG32rr, X86::CMOVGE32rr, X86::CMOVB32rr, X86::CMOVBE32rr,
X86::CMOVA32rr, X86::CMOVAE32rr, X86::CMOVP32rr, X86::CMOVNP32rr,
};
static const unsigned CMOVTABFP[] = {
X86::FCMOVE , X86::FCMOVNE, /*missing*/0, /*missing*/0,
/*missing*/0, /*missing*/0, X86::FCMOVB , X86::FCMOVBE,
X86::FCMOVA , X86::FCMOVAE, X86::FCMOVP , X86::FCMOVNP
};
if (SetCCSDNode *SetCC = dyn_cast<SetCCSDNode>(Cond)) {
if (MVT::isInteger(SetCC->getOperand(0).getValueType())) {
switch (SetCC->getCondition()) {
default: assert(0 && "Unknown integer comparison!");
case ISD::SETEQ: CondCode = EQ; break;
case ISD::SETGT: CondCode = GT; break;
case ISD::SETGE: CondCode = GE; break;
case ISD::SETLT: CondCode = LT; break;
case ISD::SETLE: CondCode = LE; break;
case ISD::SETNE: CondCode = NE; break;
case ISD::SETULT: CondCode = B; break;
case ISD::SETUGT: CondCode = A; break;
case ISD::SETULE: CondCode = BE; break;
case ISD::SETUGE: CondCode = AE; break;
}
} else {
// On a floating point condition, the flags are set as follows:
// ZF PF CF op
// 0 | 0 | 0 | X > Y
// 0 | 0 | 1 | X < Y
// 1 | 0 | 0 | X == Y
// 1 | 1 | 1 | unordered
//
switch (SetCC->getCondition()) {
default: assert(0 && "Unknown FP comparison!");
case ISD::SETUEQ:
case ISD::SETEQ: CondCode = EQ; break; // True if ZF = 1
case ISD::SETOGT:
case ISD::SETGT: CondCode = A; break; // True if CF = 0 and ZF = 0
case ISD::SETOGE:
case ISD::SETGE: CondCode = AE; break; // True if CF = 0
case ISD::SETULT:
case ISD::SETLT: CondCode = B; break; // True if CF = 1
case ISD::SETULE:
case ISD::SETLE: CondCode = BE; break; // True if CF = 1 or ZF = 1
case ISD::SETONE:
case ISD::SETNE: CondCode = NE; break; // True if ZF = 0
case ISD::SETUO: CondCode = P; break; // True if PF = 1
case ISD::SETO: CondCode = NP; break; // True if PF = 0
case ISD::SETUGT: // PF = 1 | (ZF = 0 & CF = 0)
case ISD::SETUGE: // PF = 1 | CF = 0
case ISD::SETUNE: // PF = 1 | ZF = 0
case ISD::SETOEQ: // PF = 0 & ZF = 1
case ISD::SETOLT: // PF = 0 & CF = 1
case ISD::SETOLE: // PF = 0 & (CF = 1 || ZF = 1)
// We cannot emit this comparison as a single cmov.
break;
}
}
}
unsigned Opc = 0;
if (CondCode != NOT_SET) {
switch (SVT) {
default: assert(0 && "Cannot select this type!");
case MVT::i16: Opc = CMOVTAB16[CondCode]; break;
case MVT::i32: Opc = CMOVTAB32[CondCode]; break;
case MVT::f32:
case MVT::f64: Opc = CMOVTABFP[CondCode]; ContainsFPCode = true; break;
}
}
// Finally, if we weren't able to fold this, just emit the condition and test
// it.
if (CondCode == NOT_SET || Opc == 0) {
// Get the condition into the zero flag.
unsigned CondReg = SelectExpr(Cond);
BuildMI(BB, X86::TEST8rr, 2).addReg(CondReg).addReg(CondReg);
switch (SVT) {
default: assert(0 && "Cannot select this type!");
case MVT::i16: Opc = X86::CMOVE16rr; break;
case MVT::i32: Opc = X86::CMOVE32rr; break;
case MVT::f32:
case MVT::f64: Opc = X86::FCMOVE; ContainsFPCode = true; break;
}
} else {
// FIXME: CMP R, 0 -> TEST R, R
EmitCMP(Cond.getOperand(0), Cond.getOperand(1));
}
BuildMI(BB, Opc, 2, RDest).addReg(RTrue).addReg(RFalse);
}
void ISel::EmitCMP(SDOperand LHS, SDOperand RHS) {
unsigned Tmp1 = SelectExpr(LHS), Opc;
if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(RHS)) {
@ -1232,19 +1344,7 @@ unsigned ISel::SelectExpr(SDOperand N) {
if (N.getValueType() != MVT::i1 && N.getValueType() != MVT::i8) {
Tmp2 = SelectExpr(N.getOperand(1));
Tmp3 = SelectExpr(N.getOperand(2));
Tmp1 = SelectExpr(N.getOperand(0));
switch (N.getValueType()) {
default: assert(0 && "Cannot select this type!");
case MVT::i16: Opc = X86::CMOVE16rr; break;
case MVT::i32: Opc = X86::CMOVE32rr; break;
case MVT::f32:
case MVT::f64: Opc = X86::FCMOVE; ContainsFPCode = true; break;
}
// Get the condition into the zero flag.
BuildMI(BB, X86::TEST8rr, 2).addReg(Tmp1).addReg(Tmp1);
BuildMI(BB, Opc, 2, Result).addReg(Tmp2).addReg(Tmp3);
EmitSelectCC(N.getOperand(0), N.getValueType(), Tmp2, Tmp3, Result);
return Result;
} else {
// FIXME: This should not be implemented here, it should be in the generic
@ -1253,11 +1353,9 @@ unsigned ISel::SelectExpr(SDOperand N) {
N.getOperand(1)));
Tmp3 = SelectExpr(CurDAG->getNode(ISD::ZERO_EXTEND, MVT::i16,
N.getOperand(2)));
Tmp1 = SelectExpr(N.getOperand(0));
BuildMI(BB, X86::TEST8rr, 2).addReg(Tmp1).addReg(Tmp1);
// FIXME: need subregs to do better than this!
unsigned TmpReg = MakeReg(MVT::i16);
BuildMI(BB, X86::CMOVE16rr, 2, TmpReg).addReg(Tmp2).addReg(Tmp3);
EmitSelectCC(N.getOperand(0), MVT::i16, Tmp2, Tmp3, TmpReg);
// FIXME: need subregs to do better than this!
BuildMI(BB, X86::MOV16rr, 1, X86::AX).addReg(TmpReg);
BuildMI(BB, X86::MOV8rr, 1, Result).addReg(X86::AL);
return Result;