[llvm-commits] [llvm] r56023 - /llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
Bill Wendling
isanbard at gmail.com
Tue Sep 9 15:13:54 PDT 2008
Author: void
Date: Tue Sep 9 17:13:54 2008
New Revision: 56023
URL: http://llvm.org/viewvc/llvm-project?rev=56023&view=rev
Log:
Add support for 6-, 12-, and 18-bit limited precision calculations of exp for
floating-point numbers.
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp?rev=56023&r1=56022&r2=56023&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp Tue Sep 9 17:13:54 2008
@@ -2761,7 +2761,7 @@
static SDValue
GetExponent(SelectionDAG &DAG, SDValue Op) {
SDValue t1 = DAG.getNode(ISD::AND, MVT::i32, Op,
- DAG.getConstant(0x7f800000, MVT::i32));
+ DAG.getConstant(0x7f800000, MVT::i32));
SDValue t2 = DAG.getNode(ISD::SRL, MVT::i32, t1,
DAG.getConstant(23, MVT::i32));
SDValue t3 = DAG.getNode(ISD::SUB, MVT::i32, t2,
@@ -2784,15 +2784,142 @@
return 0;
}
-/// visitExp - lower an exp intrinsic. Handles the special sequences
-/// for limited-precision mode.
+/// visitExp - Lower an exp intrinsic. Handles the special sequences for
+/// limited-precision mode.
void
SelectionDAGLowering::visitExp(CallInst &I) {
SDValue result;
- // No special expansion.
- result = DAG.getNode(ISD::FEXP,
- getValue(I.getOperand(1)).getValueType(),
- getValue(I.getOperand(1)));
+
+ if (getValue(I.getOperand(1)).getValueType() == MVT::f32 &&
+ LimitFloatPrecision > 0 && LimitFloatPrecision <= 18) {
+ SDValue Op = getValue(I.getOperand(1));
+
+ // Put the exponent in the right bit position for later addition to the
+ // final result:
+ //
+ // #define LOG2OFe 1.4426950f
+ // IntegerPartOfX = ((int32_t)(X * LOG2OFe));
+ SDValue t0 = DAG.getNode(ISD::FMUL, MVT::f32, Op,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3fb8aa3b)), MVT::f32));
+ SDValue IntegerPartOfX = DAG.getNode(ISD::FP_TO_SINT, MVT::i32, t0);
+
+ // FractionalPartOfX = (X * LOG2OFe) - (float)IntegerPartOfX;
+ SDValue t1 = DAG.getNode(ISD::SINT_TO_FP, MVT::f32, IntegerPartOfX);
+ SDValue X = DAG.getNode(ISD::FSUB, MVT::f32, t0, t1);
+
+ // IntegerPartOfX <<= 23;
+ IntegerPartOfX = DAG.getNode(ISD::SHL, MVT::i32, IntegerPartOfX,
+ DAG.getConstant(23, MVT::i32));
+
+ if (LimitFloatPrecision <= 6) {
+ // For floating-point precision of 6:
+ //
+ // TwoToFractionalPartOfX =
+ // 0.997535578f +
+ // (0.735607626f + 0.252464424f * x) * x;
+ //
+ // error 0.0144103317, which is 6 bits
+ SDValue t2 = DAG.getNode(ISD::FMUL, MVT::f32, X,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3e814304)), MVT::f32));
+ SDValue t3 = DAG.getNode(ISD::FADD, MVT::f32, t2,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3f3c50c8)), MVT::f32));
+ SDValue t4 = DAG.getNode(ISD::FMUL, MVT::f32, t3, X);
+ SDValue t5 = DAG.getNode(ISD::FADD, MVT::f32, t4,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3f7f5e7e)), MVT::f32));
+ SDValue TwoToFracPartOfX = DAG.getNode(ISD::BIT_CONVERT, MVT::i32, t5);
+
+ // Add the exponent into the result in integer domain.
+ SDValue t6 = DAG.getNode(ISD::ADD, MVT::i32,
+ TwoToFracPartOfX, IntegerPartOfX);
+
+ result = DAG.getNode(ISD::BIT_CONVERT, MVT::f32, t6);
+ } else if (LimitFloatPrecision > 6 && LimitFloatPrecision <= 12) {
+ // For floating-point precision of 12:
+ //
+ // TwoToFractionalPartOfX =
+ // 0.999892986f +
+ // (0.696457318f +
+ // (0.224338339f + 0.792043434e-1f * x) * x) * x;
+ //
+ // 0.000107046256 error, which is 13 to 14 bits
+ SDValue t2 = DAG.getNode(ISD::FMUL, MVT::f32, X,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3da235e3)), MVT::f32));
+ SDValue t3 = DAG.getNode(ISD::FADD, MVT::f32, t2,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3e65b8f3)), MVT::f32));
+ SDValue t4 = DAG.getNode(ISD::FMUL, MVT::f32, t3, X);
+ SDValue t5 = DAG.getNode(ISD::FADD, MVT::f32, t4,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3f324b07)), MVT::f32));
+ SDValue t6 = DAG.getNode(ISD::FMUL, MVT::f32, t5, X);
+ SDValue t7 = DAG.getNode(ISD::FADD, MVT::f32, t6,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3f7ff8fd)), MVT::f32));
+ SDValue TwoToFracPartOfX = DAG.getNode(ISD::BIT_CONVERT, MVT::i32, t7);
+
+ // Add the exponent into the result in integer domain.
+ SDValue t8 = DAG.getNode(ISD::ADD, MVT::i32,
+ TwoToFracPartOfX, IntegerPartOfX);
+
+ result = DAG.getNode(ISD::BIT_CONVERT, MVT::f32, t8);
+ } else { // LimitFloatPrecision > 12 && LimitFloatPrecision <= 18
+ // For floating-point precision of 18:
+ //
+ // TwoToFractionalPartOfX =
+ // 0.999999982f +
+ // (0.693148872f +
+ // (0.240227044f +
+ // (0.554906021e-1f +
+ // (0.961591928e-2f +
+ // (0.136028312e-2f + 0.157059148e-3f *x)*x)*x)*x)*x)*x;
+ //
+ // error 2.47208000*10^(-7), which is better than 18 bits
+ SDValue t2 = DAG.getNode(ISD::FMUL, MVT::f32, X,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3924b03e)), MVT::f32));
+ SDValue t3 = DAG.getNode(ISD::FADD, MVT::f32, t2,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3ab24b87)), MVT::f32));
+ SDValue t4 = DAG.getNode(ISD::FMUL, MVT::f32, t3, X);
+ SDValue t5 = DAG.getNode(ISD::FADD, MVT::f32, t4,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3c1d8c17)), MVT::f32));
+ SDValue t6 = DAG.getNode(ISD::FMUL, MVT::f32, t5, X);
+ SDValue t7 = DAG.getNode(ISD::FADD, MVT::f32, t6,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3d634a1d)), MVT::f32));
+ SDValue t8 = DAG.getNode(ISD::FMUL, MVT::f32, t7, X);
+ SDValue t9 = DAG.getNode(ISD::FADD, MVT::f32, t8,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3e75fe14)), MVT::f32));
+ SDValue t10 = DAG.getNode(ISD::FMUL, MVT::f32, t9, X);
+ SDValue t11 = DAG.getNode(ISD::FADD, MVT::f32, t10,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3f317234)), MVT::f32));
+ SDValue t12 = DAG.getNode(ISD::FMUL, MVT::f32, t11, X);
+ SDValue t13 = DAG.getNode(ISD::FADD, MVT::f32, t12,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3f800000)), MVT::f32));
+ SDValue TwoToFracPartOfX = DAG.getNode(ISD::BIT_CONVERT, MVT::i32, t13);
+
+ // Add the exponent into the result in integer domain.
+ SDValue t14 = DAG.getNode(ISD::ADD, MVT::i32,
+ TwoToFracPartOfX, IntegerPartOfX);
+
+ result = DAG.getNode(ISD::BIT_CONVERT, MVT::f32, t14);
+ }
+ } else {
+ // No special expansion.
+ result = DAG.getNode(ISD::FEXP,
+ getValue(I.getOperand(1)).getValueType(),
+ getValue(I.getOperand(1)));
+ }
+
setValue(&I, result);
}
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