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Necessary changes to codegen cttz efficiently on PowerPC

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1. Teach LegalizeDAG how to better legalize CTTZ if the target doesn't have
   CTPOP, but does have CTLZ
2. Teach PPC32 how to do sub x, const -> add x, -const for valid consts
3. Teach PPC32 how to do and (xor a, -1) b -> andc b, a
4. Teach PPC32 that ISD::CTLZ -> PPC::CNTLZW

llvm-svn: 21880
This commit is contained in:
Nate Begeman 2005-05-11 23:43:56 +00:00
parent 55937aba69
commit e84f776b5d
2 changed files with 41 additions and 9 deletions
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16
lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
View File

@ -1156,15 +1156,25 @@ SDOperand SelectionDAGLegalize::LegalizeOp(SDOperand Op) {
break;
}
case ISD::CTTZ: {
// for now, we use: { return popcount(~x & (x - 1)); }
// but see also http://www.hackersdelight.org/HDcode/ntz.cc
// for now, we use: { return popcount(~x & (x - 1)); }
// unless the target has ctlz but not ctpop, in which case we use:
// { return 32 - nlz(~x & (x-1)); }
// see also http://www.hackersdelight.org/HDcode/ntz.cc
MVT::ValueType VT = Tmp1.getValueType();
Tmp2 = DAG.getConstant(~0ULL, VT);
Tmp3 = DAG.getNode(ISD::AND, VT,
DAG.getNode(ISD::XOR, VT, Tmp1, Tmp2),
DAG.getNode(ISD::SUB, VT, Tmp1,
DAG.getConstant(1, VT)));
Result = LegalizeOp(DAG.getNode(ISD::CTPOP, VT, Tmp3));
// If ISD::CTLZ is legal and CTPOP isn't, then do that instead
if (TLI.getOperationAction(ISD::CTPOP, VT) != TargetLowering::Legal &&
TLI.getOperationAction(ISD::CTLZ, VT) == TargetLowering::Legal) {
Result = LegalizeOp(DAG.getNode(ISD::SUB, VT,
DAG.getConstant(getSizeInBits(VT), VT),
DAG.getNode(ISD::CTLZ, VT, Tmp3)));
} else {
Result = LegalizeOp(DAG.getNode(ISD::CTPOP, VT, Tmp3));
}
break;
}
default:

34
lib/Target/PowerPC/PPC32ISelPattern.cpp
View File

@ -69,10 +69,9 @@ namespace {
setOperationAction(ISD::FCOS , MVT::f32, Expand);
setOperationAction(ISD::FSQRT, MVT::f32, Expand);
//PowerPC has these, but they are not implemented
//PowerPC does not have CTPOP or CTTZ
setOperationAction(ISD::CTPOP, MVT::i32 , Expand);
setOperationAction(ISD::CTTZ , MVT::i32 , Expand);
setOperationAction(ISD::CTLZ , MVT::i32 , Expand);
setSetCCResultContents(ZeroOrOneSetCCResult);
addLegalFPImmediate(+0.0); // Necessary for FSEL
@ -654,9 +653,13 @@ static unsigned getImmediateForOpcode(SDOperand N, unsigned Opcode,
if ((v & 0x0000FFFF) == 0) { Imm = v >> 16; return 2; }
break;
case ISD::MUL:
case ISD::SUB:
if (v <= 32767 && v >= -32768) { Imm = v & 0xFFFF; return 1; }
break;
case ISD::SUB:
// handle subtract-from separately from subtract, since subi is really addi
if (U && v <= 32767 && v >= -32768) { Imm = v & 0xFFFF; return 1; }
if (!U && v <= 32768 && v >= -32767) { Imm = (-v) & 0xFFFF; return 1; }
break;
case ISD::SETCC:
if (U && (v >= 0 && v <= 65535)) { Imm = v & 0xFFFF; return 1; }
if (!U && (v <= 32767 && v >= -32768)) { Imm = v & 0xFFFF; return 1; }
@ -1817,6 +1820,11 @@ unsigned ISel::SelectExpr(SDOperand N, bool Recording) {
}
return Result;
case ISD::CTLZ:
Tmp1 = SelectExpr(N.getOperand(0));
BuildMI(BB, PPC::CNTLZW, 1, Result).addReg(Tmp1);
return Result;
case ISD::ADD:
assert (DestType == MVT::i32 && "Only do arithmetic on i32s!");
Tmp1 = SelectExpr(N.getOperand(0));
@ -1851,6 +1859,16 @@ unsigned ISel::SelectExpr(SDOperand N, bool Recording) {
switch(getImmediateForOpcode(N.getOperand(1), opcode, Tmp2)) {
default: assert(0 && "unhandled result code");
case 0: // No immediate
// Check for andc: and, (xor a, -1), b
if (N.getOperand(0).getOpcode() == ISD::XOR &&
N.getOperand(0).getOperand(1).getOpcode() == ISD::Constant &&
cast<ConstantSDNode>(N.getOperand(0).getOperand(1))->isAllOnesValue()) {
Tmp1 = SelectExpr(N.getOperand(0).getOperand(0));
Tmp2 = SelectExpr(N.getOperand(1));
BuildMI(BB, PPC::ANDC, 2, Result).addReg(Tmp2).addReg(Tmp1);
return Result;
}
// It wasn't and-with-complement, emit a regular and
Tmp1 = SelectExpr(N.getOperand(0));
Tmp2 = SelectExpr(N.getOperand(1));
Opc = Recording ? PPC::ANDo : PPC::AND;
@ -1976,11 +1994,15 @@ unsigned ISel::SelectExpr(SDOperand N, bool Recording) {
}
case ISD::SUB:
Tmp2 = SelectExpr(N.getOperand(1));
if (1 == getImmediateForOpcode(N.getOperand(0), opcode, Tmp1))
if (1 == getImmediateForOpcode(N.getOperand(0), opcode, Tmp1, true)) {
Tmp2 = SelectExpr(N.getOperand(1));
BuildMI(BB, PPC::SUBFIC, 2, Result).addReg(Tmp2).addSImm(Tmp1);
else {
} else if (1 == getImmediateForOpcode(N.getOperand(1), opcode, Tmp2)) {
Tmp1 = SelectExpr(N.getOperand(0));
BuildMI(BB, PPC::ADDI, 2, Result).addReg(Tmp1).addSImm(Tmp2);
} else {
Tmp1 = SelectExpr(N.getOperand(0));
Tmp2 = SelectExpr(N.getOperand(1));
BuildMI(BB, PPC::SUBF, 2, Result).addReg(Tmp2).addReg(Tmp1);
}
return Result;