[llvm-commits] [llvm] r55968 - /llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
Bill Wendling
isanbard at gmail.com
Mon Sep 8 17:28:24 PDT 2008
Author: void
Date: Mon Sep 8 19:28:24 2008
New Revision: 55968
URL: http://llvm.org/viewvc/llvm-project?rev=55968&view=rev
Log:
Add support for floating-point calculations of log2 with limited precisions of 6
and 18.
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=55968&r1=55967&r2=55968&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp Mon Sep 8 19:28:24 2008
@@ -2755,7 +2755,6 @@
/// visitExp - lower an exp intrinsic. Handles the special sequences
/// for limited-precision mode.
-
void
SelectionDAGLowering::visitExp(CallInst &I) {
SDValue result;
@@ -2768,7 +2767,6 @@
/// visitLog - lower a log intrinsic. Handles the special sequences
/// for limited-precision mode.
-
void
SelectionDAGLowering::visitLog(CallInst &I) {
SDValue result;
@@ -2779,108 +2777,225 @@
setValue(&I, result);
}
-/// visitLog2 - lower a log2 intrinsic. Handles the special sequences
-/// for limited-precision mode.
-
+/// visitLog2 - Lower a log2 intrinsic. Handles the special sequences for
+/// limited-precision mode.
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));
+ LimitFloatPrecision > 0 && LimitFloatPrecision <= 18) {
+ SDValue Op = getValue(I.getOperand(1));
+ SDValue Op1 = DAG.getNode(ISD::BIT_CONVERT, MVT::i32, Op);
+
+ // Get the exponent, which is most of log and scale by log(2):
+ //
+ // LogOfExponent = (float) (((Op1 & 0x7f800000) >> 23) - 127);
+ //
+ // where Op1 is the hexidecimal representation of floating point value.
+ SDValue t0 = DAG.getNode(ISD::AND, MVT::i32, Op1,
+ DAG.getConstant(0x7f800000, MVT::i32));
+ SDValue t1 = DAG.getNode(ISD::SRL, MVT::i32, t0,
+ DAG.getConstant(23, 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::FMUL, MVT::f32, t6,
- DAG.getConstantFP(APFloat(
- APInt(32, 0xbda7262e)), MVT::f32));
- SDValue t8 = DAG.getNode(ISD::FADD, MVT::f32, t7,
- DAG.getConstantFP(APFloat(
- APInt(32, 0x3f25280b)), MVT::f32));
- SDValue t9 = DAG.getNode(ISD::FMUL, MVT::f32, t8, t6);
- SDValue t10 = DAG.getNode(ISD::FSUB, MVT::f32, t9,
- DAG.getConstantFP(APFloat(
- APInt(32, 0x4007b923)), MVT::f32));
- SDValue t11 = DAG.getNode(ISD::FMUL, MVT::f32, t10, t6);
- SDValue t12 = DAG.getNode(ISD::FADD, MVT::f32, t11,
- DAG.getConstantFP(APFloat(
- APInt(32, 0x40823e2f)), MVT::f32));
- SDValue t13 = DAG.getNode(ISD::FMUL, MVT::f32, t12, t6);
- SDValue t14 = DAG.getNode(ISD::FSUB, MVT::f32, t13,
- DAG.getConstantFP(APFloat(
- APInt(32, 0x4020d29c)), MVT::f32));
- result = DAG.getNode(ISD::FADD, MVT::f32, t3, t14);
+ DAG.getConstant(127, MVT::i32));
+ SDValue LogOfExponent = DAG.getNode(ISD::UINT_TO_FP, MVT::f32, t2);
+
+ // Get the significand and build it into a floating-point number with
+ // exponent of 1:
+ //
+ // Op1 = (Op1 & 0x007fffff) | 0x3f800000;
+ //
+ // where Op1 is the hexidecimal representation of floating point value.
+ SDValue t4 = DAG.getNode(ISD::AND, MVT::i32, Op1,
+ DAG.getConstant(0x007fffff, MVT::i32));
+ SDValue t5 = DAG.getNode(ISD::OR, MVT::i32, t4,
+ DAG.getConstant(0x3f800000, MVT::i32));
+ SDValue X = DAG.getNode(ISD::BIT_CONVERT, MVT::f32, t5);
+
+ // Different possible minimax approximations of significand in
+ // floating-point for various degrees of accuracy over [1,2].
+ if (LimitFloatPrecision <= 6) {
+ // For floating-point precision of 6:
+ //
+ // Log2ofMantissa = -1.6749035f + (2.0246817f - .34484768f * x) * x;
+ //
+ // error 0.0049451742, which is more than 7 bits
+ SDValue t8 = DAG.getNode(ISD::FMUL, MVT::f32, X,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0xbeb08fe0)), MVT::f32));
+ SDValue t9 = DAG.getNode(ISD::FADD, MVT::f32, t8,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x40019463)), MVT::f32));
+ SDValue t10 = DAG.getNode(ISD::FMUL, MVT::f32, t9, X);
+ SDValue Log2ofMantissa = DAG.getNode(ISD::FSUB, MVT::f32, t10,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3fd6633d)), MVT::f32));
+
+ result = DAG.getNode(ISD::FADD, MVT::f32, LogOfExponent, Log2ofMantissa);
+ } else if (LimitFloatPrecision > 6 && LimitFloatPrecision <= 12) {
+ // For floating-point precision of 12:
+ //
+ // Log2ofMantissa =
+ // -2.51285454f +
+ // (4.07009056f +
+ // (-2.12067489f +
+ // (.645142248f - 0.816157886e-1f * x) * x) * x) * x;
+ //
+ // error 0.0000876136000, which is better than 13 bits
+ SDValue t8 = DAG.getNode(ISD::FMUL, MVT::f32, X,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0xbda7262e)), MVT::f32));
+ SDValue t9 = DAG.getNode(ISD::FADD, MVT::f32, t8,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3f25280b)), MVT::f32));
+ SDValue t10 = DAG.getNode(ISD::FMUL, MVT::f32, t9, X);
+ SDValue t11 = DAG.getNode(ISD::FSUB, MVT::f32, t10,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x4007b923)), 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, 0x40823e2f)), MVT::f32));
+ SDValue t14 = DAG.getNode(ISD::FMUL, MVT::f32, t13, X);
+ SDValue Log2ofMantissa = DAG.getNode(ISD::FSUB, MVT::f32, t14,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x4020d29c)), MVT::f32));
+
+ result = DAG.getNode(ISD::FADD, MVT::f32, LogOfExponent, Log2ofMantissa);
+ } else { // LimitFloatPrecision > 12 && LimitFloatPrecision <= 18
+ // For floating-point precision of 18:
+ //
+ // Log2ofMantissa =
+ // -3.0400495f +
+ // (6.1129976f +
+ // (-5.3420409f +
+ // (3.2865683f +
+ // (-1.2669343f +
+ // (0.27515199f -
+ // 0.25691327e-1f * x) * x) * x) * x) * x) * x;
+ //
+ // error 0.0000018516, which is better than 18 bits
+ SDValue t8 = DAG.getNode(ISD::FMUL, MVT::f32, X,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0xbcd2769e)), MVT::f32));
+ SDValue t9 = DAG.getNode(ISD::FADD, MVT::f32, t8,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3e8ce0b9)), MVT::f32));
+ SDValue t10 = DAG.getNode(ISD::FMUL, MVT::f32, t9, X);
+ SDValue t11 = DAG.getNode(ISD::FSUB, MVT::f32, t10,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3fa22ae7)), 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, 0x40525723)), MVT::f32));
+ SDValue t14 = DAG.getNode(ISD::FMUL, MVT::f32, t13, X);
+ SDValue t15 = DAG.getNode(ISD::FSUB, MVT::f32, t14,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x40aaf200)), MVT::f32));
+ SDValue t16 = DAG.getNode(ISD::FMUL, MVT::f32, t15, X);
+ SDValue t17 = DAG.getNode(ISD::FADD, MVT::f32, t16,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x40c39dad)), MVT::f32));
+ SDValue t18 = DAG.getNode(ISD::FMUL, MVT::f32, t17, X);
+ SDValue Log2ofMantissa = DAG.getNode(ISD::FSUB, MVT::f32, t18,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x4042902c)), MVT::f32));
+
+ result = DAG.getNode(ISD::FADD, MVT::f32, LogOfExponent, Log2ofMantissa);
+ }
} else {
- // No special expansion.
+ // No special expansion.
result = DAG.getNode(ISD::FLOG2,
getValue(I.getOperand(1)).getValueType(),
getValue(I.getOperand(1)));
}
+
setValue(&I, result);
}
-/// visitLog10 - lower a log10 intrinsic. Handles the special sequences
-/// for limited-precision mode.
-
+/// visitLog10 - Lower a log10 intrinsic. Handles the special sequences for
+/// limited-precision mode.
void
SelectionDAGLowering::visitLog10(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));
+ LimitFloatPrecision > 0 && LimitFloatPrecision <= 18) {
+ SDValue Op = getValue(I.getOperand(1));
+ SDValue Op1 = DAG.getNode(ISD::BIT_CONVERT, MVT::i32, Op);
+
+ // Get the exponent, which is most of log10 and scale by log10(2).
+ //
+ // #define LOG10OF2 0.30102999f
+ // Log10ofExponent = (float)(((Op1 & 0x7f800000) >> 23) - 127) * LOG10OF2;
+ //
+ // where Op1 is the hexidecimal value of the floating-point number.
+ SDValue t0 = DAG.getNode(ISD::AND, MVT::i32, Op1,
+ DAG.getConstant(0x7f800000, MVT::i32));
+ SDValue t1 = DAG.getNode(ISD::SRL, MVT::i32, t0,
+ DAG.getConstant(23, MVT::i32));
SDValue t2 = DAG.getNode(ISD::SUB, MVT::i32, t1,
- DAG.getConstant(127, MVT::i32));
+ DAG.getConstant(127, MVT::i32));
SDValue t3 = DAG.getNode(ISD::UINT_TO_FP, MVT::f32, t2);
- SDValue t4 = DAG.getNode(ISD::FMUL, MVT::f32, t3,
- DAG.getConstantFP(APFloat(
- APInt(32, 0x3e9a209a)), MVT::f32));
- SDValue t5 = DAG.getNode(ISD::OR, MVT::i32, operand1,
- DAG.getConstant(1065353216, MVT::i32));
- SDValue t6 = DAG.getNode(ISD::AND, MVT::i32, t5,
- DAG.getConstant(1073741823, MVT::i32));
- SDValue t7 = DAG.getNode(ISD::BIT_CONVERT, MVT::f32, t6);
- SDValue t8 = DAG.getNode(ISD::FMUL, MVT::f32, t7,
- DAG.getConstantFP(APFloat(
- APInt(32, 0x3d431f31)), MVT::f32));
- SDValue t9 = DAG.getNode(ISD::FSUB, MVT::f32, t8,
- DAG.getConstantFP(APFloat(
- APInt(32, 0x3ea21fb2)), MVT::f32));
- SDValue t10 = DAG.getNode(ISD::FMUL, MVT::f32, t9, t7);
- SDValue t11 = DAG.getNode(ISD::FADD, MVT::f32, t10,
- DAG.getConstantFP(APFloat(
- APInt(32, 0x3f6ae232)), MVT::f32));
- SDValue t12 = DAG.getNode(ISD::FMUL, MVT::f32, t11, t7);
- SDValue t13 = DAG.getNode(ISD::FSUB, MVT::f32, t12,
- DAG.getConstantFP(APFloat(
- APInt(32, 0x3f25f7c3)), MVT::f32));
- result = DAG.getNode(ISD::FADD, MVT::f32, t4, t13);
+ SDValue LogOfExponent = DAG.getNode(ISD::FMUL, MVT::f32, t3,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3e9a209a)), MVT::f32));
+
+ // Get the significand and build it into a floating-point number with
+ // exponent of 1:
+ //
+ // Op1 = (Op1 & 0x007fffff) | 0x3f800000;
+ //
+ // where Op1 is the hexidecimal representation of floating point value.
+ SDValue t4 = DAG.getNode(ISD::AND, MVT::i32, Op1,
+ DAG.getConstant(0x007fffff, MVT::i32));
+ SDValue t5 = DAG.getNode(ISD::OR, MVT::i32, t4,
+ DAG.getConstant(0x3f800000, MVT::i32));
+ SDValue X = DAG.getNode(ISD::BIT_CONVERT, MVT::f32, t5);
+
+ if (LimitFloatPrecision <= 6) {
+ } else if (LimitFloatPrecision > 6 && LimitFloatPrecision <= 12) {
+ // For floating-point precision of 12:
+ //
+ // Log10ofMantissa =
+ // -0.64831180f +
+ // (0.91751397f +
+ // (-0.31664806f + 0.47637168e-1f * x) * x) * x;
+ //
+ // error 0.00019228036, which is better than 12 bits
+ SDValue t6 = DAG.getNode(ISD::FMUL, MVT::f32, X,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3d431f31)), MVT::f32));
+ SDValue t7 = DAG.getNode(ISD::FSUB, MVT::f32, t6,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3ea21fb2)), 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, 0x3f6ae232)), MVT::f32));
+ SDValue t10 = DAG.getNode(ISD::FMUL, MVT::f32, t9, X);
+ SDValue t11 = DAG.getNode(ISD::FSUB, MVT::f32, t10,
+ DAG.getConstantFP(APFloat(
+ APInt(32, 0x3f25f7c3)), MVT::f32));
+ SDValue Log10ofMantissa = DAG.getNode(ISD::FP_ROUND, MVT::f32, t11,
+ DAG.getConstant(0, MVT::i32));
+
+ result = DAG.getNode(ISD::FADD, MVT::f32, LogOfExponent, Log10ofMantissa);
+ } else { // LimitFloatPrecision > 12 && LimitFloatPrecision <= 18
+ }
} else {
- // No special expansion.
+ // No special expansion.
result = DAG.getNode(ISD::FLOG10,
getValue(I.getOperand(1)).getValueType(),
getValue(I.getOperand(1)));
}
+
setValue(&I, result);
}
/// visitExp2 - lower an exp2 intrinsic. Handles the special sequences
/// for limited-precision mode.
-
void
SelectionDAGLowering::visitExp2(CallInst &I) {
SDValue result;
@@ -2910,7 +3025,7 @@
SDValue t11 = DAG.getNode(ISD::ADD, MVT::i32, t10, t3);
result = DAG.getNode(ISD::BIT_CONVERT, MVT::f32, t11);
} else {
- // No special expansion.
+ // No special expansion.
result = DAG.getNode(ISD::FEXP2,
getValue(I.getOperand(1)).getValueType(),
getValue(I.getOperand(1)));
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