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author | rofl0r <retnyg@gmx.net> | 2014-01-07 22:43:34 +0100 |
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committer | rofl0r <retnyg@gmx.net> | 2014-02-23 11:07:18 +0100 |
commit | 323272db175204b951f119dae4bd99ef05e20f13 (patch) | |
tree | 70329156d5189294b1e9e7f9c7c326924ad62e35 /src/math/x32/expl.s | |
parent | 0f169cbb79c39a5b15f7a27d9283cdeb6e122b8f (diff) | |
download | musl-323272db175204b951f119dae4bd99ef05e20f13.tar.gz musl-323272db175204b951f119dae4bd99ef05e20f13.tar.bz2 musl-323272db175204b951f119dae4bd99ef05e20f13.tar.xz musl-323272db175204b951f119dae4bd99ef05e20f13.zip |
import vanilla x86_64 code as x32
Diffstat (limited to 'src/math/x32/expl.s')
-rw-r--r-- | src/math/x32/expl.s | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/src/math/x32/expl.s b/src/math/x32/expl.s new file mode 100644 index 00000000..3add810d --- /dev/null +++ b/src/math/x32/expl.s @@ -0,0 +1,101 @@ +# exp(x) = 2^hi + 2^hi (2^lo - 1) +# where hi+lo = log2e*x with 128bit precision +# exact log2e*x calculation depends on nearest rounding mode +# using the exact multiplication method of Dekker and Veltkamp + +.global expl +.type expl,@function +expl: + fldt 8(%rsp) + + # interesting case: 0x1p-32 <= |x| < 16384 + # check if (exponent|0x8000) is in [0xbfff-32, 0xbfff+13] + mov 16(%rsp), %ax + or $0x8000, %ax + sub $0xbfdf, %ax + cmp $45, %ax + jbe 2f + test %ax, %ax + fld1 + js 1f + # if |x|>=0x1p14 or nan return 2^trunc(x) + fscale + fstp %st(1) + ret + # if |x|<0x1p-32 return 1+x +1: faddp + ret + + # should be 0x1.71547652b82fe178p0L == 0x3fff b8aa3b29 5c17f0bc + # it will be wrong on non-nearest rounding mode +2: fldl2e + subq $48, %rsp + # hi = log2e_hi*x + # 2^hi = exp2l(hi) + fmul %st(1),%st + fld %st(0) + fstpt (%rsp) + fstpt 16(%rsp) + fstpt 32(%rsp) + call exp2l + # if 2^hi == inf return 2^hi + fld %st(0) + fstpt (%rsp) + cmpw $0x7fff, 8(%rsp) + je 1f + fldt 32(%rsp) + fldt 16(%rsp) + # fpu stack: 2^hi x hi + # exact mult: x*log2e + fld %st(1) + # c = 0x1p32+1 + movq $0x41f0000000100000,%rax + pushq %rax + fldl (%rsp) + # xh = x - c*x + c*x + # xl = x - xh + fmulp + fld %st(2) + fsub %st(1), %st + faddp + fld %st(2) + fsub %st(1), %st + # yh = log2e_hi - c*log2e_hi + c*log2e_hi + movq $0x3ff7154765200000,%rax + pushq %rax + fldl (%rsp) + # fpu stack: 2^hi x hi xh xl yh + # lo = hi - xh*yh + xl*yh + fld %st(2) + fmul %st(1), %st + fsubp %st, %st(4) + fmul %st(1), %st + faddp %st, %st(3) + # yl = log2e_hi - yh + movq $0x3de705fc2f000000,%rax + pushq %rax + fldl (%rsp) + # fpu stack: 2^hi x lo xh xl yl + # lo += xh*yl + xl*yl + fmul %st, %st(2) + fmulp %st, %st(1) + fxch %st(2) + faddp + faddp + # log2e_lo + movq $0xbfbe,%rax + pushq %rax + movq $0x82f0025f2dc582ee,%rax + pushq %rax + fldt (%rsp) + addq $40,%rsp + # fpu stack: 2^hi x lo log2e_lo + # lo += log2e_lo*x + # return 2^hi + 2^hi (2^lo - 1) + fmulp %st, %st(2) + faddp + f2xm1 + fmul %st(1), %st + faddp +1: addq $48, %rsp + ret |