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Next limited float precision expansion (log2 12 bits)

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55866 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen 2008-09-05 23:49:37 +00:00
parent 6e6074508c
commit 853244f8a6
1 changed files with 43 additions and 3 deletions
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46
lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
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@ -2785,10 +2785,50 @@ SelectionDAGLowering::visitLog(CallInst &I) {
void
SelectionDAGLowering::visitLog2(CallInst &I) {
SDValue result;
if (getValue(I.getOperand(1)).getValueType() == MVT::f32 &&
LimitFloatPrecision>0 && LimitFloatPrecision<=12) {
SDValue operand = getValue(I.getOperand(1));
SDValue operand1 = DAG.getNode(ISD::BIT_CONVERT, MVT::i32, operand);
SDValue t0 = DAG.getNode(ISD::SRL, MVT::i32, operand1,
DAG.getConstant(23, MVT::i32));
SDValue t1 = DAG.getNode(ISD::AND, MVT::i32, t0,
DAG.getConstant(255, MVT::i32));
SDValue t2 = DAG.getNode(ISD::SUB, MVT::i32, t1,
DAG.getConstant(127, MVT::i32));
SDValue t3 = DAG.getNode(ISD::UINT_TO_FP, MVT::f32, t2);
SDValue t4 = DAG.getNode(ISD::OR, MVT::i32, operand1,
DAG.getConstant(1065353216, MVT::i32));
SDValue t5 = DAG.getNode(ISD::AND, MVT::i32, t4,
DAG.getConstant(1073741823, MVT::i32));
SDValue t6 = DAG.getNode(ISD::BIT_CONVERT, MVT::f32, t5);
SDValue t7 = DAG.getNode(ISD::FP_EXTEND, MVT::f64, t6);
SDValue t8 = DAG.getNode(ISD::FMUL, MVT::f64, t7,
DAG.getConstantFP(APFloat(
APInt(64, 0xbfb4e4c5b6dfced3ULL)), MVT::f64));
SDValue t9 = DAG.getNode(ISD::FADD, MVT::f64, t8,
DAG.getConstantFP(APFloat(
APInt(64, 0x3fe4a5015b0db188ULL)), MVT::f64));
SDValue t10 = DAG.getNode(ISD::FMUL, MVT::f64, t9, t7);
SDValue t11 = DAG.getNode(ISD::FSUB, MVT::f64, t10,
DAG.getConstantFP(APFloat(
APInt(64, 0x4000f724658ffcb8ULL)), MVT::f64));
SDValue t12 = DAG.getNode(ISD::FMUL, MVT::f64, t11, t7);
SDValue t13 = DAG.getNode(ISD::FADD, MVT::f64, t12,
DAG.getConstantFP(APFloat(
APInt(64, 0x401047c5d1dbd553ULL)), MVT::f64));
SDValue t14 = DAG.getNode(ISD::FMUL, MVT::f64, t13, t7);
SDValue t15 = DAG.getNode(ISD::FSUB, MVT::f64, t14,
DAG.getConstantFP(APFloat(
APInt(64, 0x40041a537b273db2ULL)), MVT::f64));
SDValue t16 = DAG.getNode(ISD::FP_ROUND, MVT::f32, t15,
DAG.getConstant(0, MVT::i32));
result = DAG.getNode(ISD::FADD, MVT::f32, t3, t16);
} else {
// No special expansion.
result = DAG.getNode(ISD::FLOG2,
getValue(I.getOperand(1)).getValueType(),
getValue(I.getOperand(1)));
result = DAG.getNode(ISD::FLOG2,
getValue(I.getOperand(1)).getValueType(),
getValue(I.getOperand(1)));
}
setValue(&I, result);
}