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authorSzabolcs Nagy <nsz@port70.net>2013-08-15 10:54:56 +0000
committerSzabolcs Nagy <nsz@port70.net>2013-08-15 10:54:56 +0000
commit1b3973fb43fbef80dab1dfc9c788783e78ab5043 (patch)
tree5c5355c3b96ef9313343eddf2b69674ea78ba518 /src/math/x86_64
parentc599f4f4d705ba215a2672b92baa1c29d9dd0735 (diff)
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math: fix x86 expl.s to raise underflow and clean up special case handling
Diffstat (limited to 'src/math/x86_64')
-rw-r--r--src/math/x86_64/expl.s37
1 files changed, 15 insertions, 22 deletions
diff --git a/src/math/x86_64/expl.s b/src/math/x86_64/expl.s
index 6d5c1ceb..107f3f52 100644
--- a/src/math/x86_64/expl.s
+++ b/src/math/x86_64/expl.s
@@ -8,32 +8,25 @@
expl:
fldt 8(%rsp)
- # special cases: 2*x is +-inf, nan or |x| < 0x1p-32
- # check (exponent|0x8000)+2 < 0xbfff+2-32
- movw 16(%rsp), %ax
- movw %ax, %dx
- orw $0x8000, %dx
- addw $2, %dx
- cmpw $0xbfff-30, %dx
- jnb 3f
- cmpw $1, %dx
- jbe 1f
- # if |x|<0x1p-32 return 1+x
+ # 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
- jmp 2f
-1: testw %ax, %ax
- jns 1f
- # if 2*x == -inf,-nan return -0/x
- fldz
- fchs
- fdivp
+ js 1f
+ # if |x|>=0x1p14 or nan return 2^trunc(x)
+ fscale
+ fstp %st(1)
ret
- # if 2*x == inf,nan return 2*x
-1: fld %st(0)
-2: faddp
+ # if |x|<0x1p-32 return 1+x
+1: faddp
ret
- # should be 0x1.71547652b82fe178p0 == 0x3fff b8aa3b29 5c17f0bc
+ # should be 0x1.71547652b82fe178p0L == 0x3fff b8aa3b29 5c17f0bc
# it will be wrong on non-nearest rounding mode
3: fldl2e
subq $48, %rsp