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Diffstat (limited to 'src/math/log_amd64.s')
| -rw-r--r-- | src/math/log_amd64.s | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/src/math/log_amd64.s b/src/math/log_amd64.s new file mode 100644 index 000000000..84c60ab4d --- /dev/null +++ b/src/math/log_amd64.s @@ -0,0 +1,111 @@ +// Copyright 2010 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +#include "textflag.h" + +#define HSqrt2 7.07106781186547524401e-01 // sqrt(2)/2 +#define Ln2Hi 6.93147180369123816490e-01 // 0x3fe62e42fee00000 +#define Ln2Lo 1.90821492927058770002e-10 // 0x3dea39ef35793c76 +#define L1 6.666666666666735130e-01 // 0x3FE5555555555593 +#define L2 3.999999999940941908e-01 // 0x3FD999999997FA04 +#define L3 2.857142874366239149e-01 // 0x3FD2492494229359 +#define L4 2.222219843214978396e-01 // 0x3FCC71C51D8E78AF +#define L5 1.818357216161805012e-01 // 0x3FC7466496CB03DE +#define L6 1.531383769920937332e-01 // 0x3FC39A09D078C69F +#define L7 1.479819860511658591e-01 // 0x3FC2F112DF3E5244 +#define NaN 0x7FF8000000000001 +#define NegInf 0xFFF0000000000000 +#define PosInf 0x7FF0000000000000 + +// func Log(x float64) float64 +TEXT ·Log(SB),NOSPLIT,$0 + // test bits for special cases + MOVQ x+0(FP), BX + MOVQ $~(1<<63), AX // sign bit mask + ANDQ BX, AX + JEQ isZero + MOVQ $0, AX + CMPQ AX, BX + JGT isNegative + MOVQ $PosInf, AX + CMPQ AX, BX + JLE isInfOrNaN + // f1, ki := math.Frexp(x); k := float64(ki) + MOVQ BX, X0 + MOVQ $0x000FFFFFFFFFFFFF, AX + MOVQ AX, X2 + ANDPD X0, X2 + MOVSD $0.5, X0 // 0x3FE0000000000000 + ORPD X0, X2 // X2= f1 + SHRQ $52, BX + ANDL $0x7FF, BX + SUBL $0x3FE, BX + CVTSL2SD BX, X1 // x1= k, x2= f1 + // if f1 < math.Sqrt2/2 { k -= 1; f1 *= 2 } + MOVSD $HSqrt2, X0 // x0= 0.7071, x1= k, x2= f1 + CMPSD X2, X0, 5 // cmpnlt; x0= 0 or ^0, x1= k, x2 = f1 + MOVSD $1.0, X3 // x0= 0 or ^0, x1= k, x2 = f1, x3= 1 + ANDPD X0, X3 // x0= 0 or ^0, x1= k, x2 = f1, x3= 0 or 1 + SUBSD X3, X1 // x0= 0 or ^0, x1= k, x2 = f1, x3= 0 or 1 + MOVSD $1.0, X0 // x0= 1, x1= k, x2= f1, x3= 0 or 1 + ADDSD X0, X3 // x0= 1, x1= k, x2= f1, x3= 1 or 2 + MULSD X3, X2 // x0= 1, x1= k, x2= f1 + // f := f1 - 1 + SUBSD X0, X2 // x1= k, x2= f + // s := f / (2 + f) + MOVSD $2.0, X0 + ADDSD X2, X0 + MOVAPD X2, X3 + DIVSD X0, X3 // x1=k, x2= f, x3= s + // s2 := s * s + MOVAPD X3, X4 // x1= k, x2= f, x3= s + MULSD X4, X4 // x1= k, x2= f, x3= s, x4= s2 + // s4 := s2 * s2 + MOVAPD X4, X5 // x1= k, x2= f, x3= s, x4= s2 + MULSD X5, X5 // x1= k, x2= f, x3= s, x4= s2, x5= s4 + // t1 := s2 * (L1 + s4*(L3+s4*(L5+s4*L7))) + MOVSD $L7, X6 + MULSD X5, X6 + ADDSD $L5, X6 + MULSD X5, X6 + ADDSD $L3, X6 + MULSD X5, X6 + ADDSD $L1, X6 + MULSD X6, X4 // x1= k, x2= f, x3= s, x4= t1, x5= s4 + // t2 := s4 * (L2 + s4*(L4+s4*L6)) + MOVSD $L6, X6 + MULSD X5, X6 + ADDSD $L4, X6 + MULSD X5, X6 + ADDSD $L2, X6 + MULSD X6, X5 // x1= k, x2= f, x3= s, x4= t1, x5= t2 + // R := t1 + t2 + ADDSD X5, X4 // x1= k, x2= f, x3= s, x4= R + // hfsq := 0.5 * f * f + MOVSD $0.5, X0 + MULSD X2, X0 + MULSD X2, X0 // x0= hfsq, x1= k, x2= f, x3= s, x4= R + // return k*Ln2Hi - ((hfsq - (s*(hfsq+R) + k*Ln2Lo)) - f) + ADDSD X0, X4 // x0= hfsq, x1= k, x2= f, x3= s, x4= hfsq+R + MULSD X4, X3 // x0= hfsq, x1= k, x2= f, x3= s*(hfsq+R) + MOVSD $Ln2Lo, X4 + MULSD X1, X4 // x4= k*Ln2Lo + ADDSD X4, X3 // x0= hfsq, x1= k, x2= f, x3= s*(hfsq+R)+k*Ln2Lo + SUBSD X3, X0 // x0= hfsq-(s*(hfsq+R)+k*Ln2Lo), x1= k, x2= f + SUBSD X2, X0 // x0= (hfsq-(s*(hfsq+R)+k*Ln2Lo))-f, x1= k + MULSD $Ln2Hi, X1 // x0= (hfsq-(s*(hfsq+R)+k*Ln2Lo))-f, x1= k*Ln2Hi + SUBSD X0, X1 // x1= k*Ln2Hi-((hfsq-(s*(hfsq+R)+k*Ln2Lo))-f) + MOVSD X1, ret+8(FP) + RET +isInfOrNaN: + MOVQ BX, ret+8(FP) // +Inf or NaN, return x + RET +isNegative: + MOVQ $NaN, AX + MOVQ AX, ret+8(FP) // return NaN + RET +isZero: + MOVQ $NegInf, AX + MOVQ AX, ret+8(FP) // return -Inf + RET |