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| author | Wèi Cōngruì <crvv.mail@gmail.com> | 2018-01-09 11:48:15 +0800 |
|---|---|---|
| committer | Robert Griesemer <gri@golang.org> | 2018-03-29 07:03:09 +0000 |
| commit | 7fe2f549cc10e1251bc84a5c0b99668ca73589a8 (patch) | |
| tree | 457f33798ff87d4a92d23d2b01631ba25b90335c /src/math | |
| parent | 4907c62f99fbfc8608a79a17c20d89f50956d9fc (diff) | |
| download | go-7fe2f549cc10e1251bc84a5c0b99668ca73589a8.tar.xz | |
math: handle denormals in AMD64 Exp
Fixes #23164
Change-Id: I6e8c6443f3ef91df71e117cce1cfa1faba647dd7
Reviewed-on: https://go-review.googlesource.com/87337
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Diffstat (limited to 'src/math')
| -rw-r--r-- | src/math/all_test.go | 3 | ||||
| -rw-r--r-- | src/math/exp_amd64.s | 25 |
2 files changed, 19 insertions, 9 deletions
diff --git a/src/math/all_test.go b/src/math/all_test.go index 39b5b33071..a145c5e60b 100644 --- a/src/math/all_test.go +++ b/src/math/all_test.go @@ -1014,6 +1014,8 @@ var vfexpSC = []float64{ 1, // near zero 3.725290298461915e-09, + // denormal + -740, } var expSC = []float64{ 0, @@ -1026,6 +1028,7 @@ var expSC = []float64{ Inf(1), 2.718281828459045, 1.0000000037252903, + 4.2e-322, } var vfexp2SC = []float64{ diff --git a/src/math/exp_amd64.s b/src/math/exp_amd64.s index 2f7fd76fe4..1c2ac8f676 100644 --- a/src/math/exp_amd64.s +++ b/src/math/exp_amd64.s @@ -96,14 +96,13 @@ TEXT ·Exp(SB),NOSPLIT,$0 MULSD X1, X0 ADDSD exprodata<>+8(SB), X0 // return fr * 2**exponent -lastStep: - MOVL $0x3FF, AX // bias - ADDL AX, BX - JLE underflow +ldexp: + ADDL $0x3FF, BX // add bias + JLE denormal CMPL BX, $0x7FF JGE overflow - MOVL $52, CX - SHLQ CX, BX +lastStep: + SHLQ $52, BX MOVQ BX, X1 MULSD X1, X0 MOVSD X0, ret+8(FP) @@ -115,14 +114,22 @@ notFinite: JNE notNegInf // -Inf, return 0 underflow: // return 0 - MOVQ $0, AX - MOVQ AX, ret+8(FP) + MOVQ $0, ret+8(FP) RET overflow: // return +Inf MOVQ $PosInf, BX notNegInf: // NaN or +Inf, return x MOVQ BX, ret+8(FP) RET +denormal: + CMPL BX, $-52 + JL underflow + ADDL $0x3FE, BX // add bias - 1 + SHLQ $52, BX + MOVQ BX, X1 + MULSD X1, X0 + MOVQ $1, BX + JMP lastStep avxfma: MOVSD $LN2U, X2 @@ -149,4 +156,4 @@ avxfma: MULSD X1, X0 VADDSD exprodata<>+16(SB), X0, X1 VFMADD213SD exprodata<>+8(SB), X1, X0 - JMP lastStep + JMP ldexp |