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authornsz <nsz@port70.net>2012-08-08 20:18:16 +0200
committernsz <nsz@port70.net>2012-08-08 20:18:16 +0200
commit1fb01691547e85be253a4f1543be3920de651e27 (patch)
treec7957da95fa496f77fea7e118faa1440003825ce /src/math/i386/exp.s
parentae0b9da48c91087c5ab78e4918deb69665d0ccc6 (diff)
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math: fix exp.s on i386 and x86_64 so the exception flags are correct
exp(inf), exp(-inf), exp(nan) used to raise wrong flags
Diffstat (limited to 'src/math/i386/exp.s')
-rw-r--r--src/math/i386/exp.s39
1 files changed, 18 insertions, 21 deletions
diff --git a/src/math/i386/exp.s b/src/math/i386/exp.s
index ca0de1d4..c7f5ad0f 100644
--- a/src/math/i386/exp.s
+++ b/src/math/i386/exp.s
@@ -69,18 +69,18 @@ exp:
exp2:
fldl 4(%esp)
1: pushl $0x467ff000
- flds (%esp)
+ flds (%esp) # 16380
xorl %eax,%eax
pushl $0x80000000
push %eax
fld %st(1)
fabs
- fucom %st(1)
+ fucomp %st(1)
fnstsw
fstp %st(0)
- fstp %st(0)
sahf
- ja 2f
+ ja 3f # |x| > 16380
+ jp 2f # x is nan (avoid invalid except in fistp)
fld %st(0)
fistpl 8(%esp)
fildl 8(%esp)
@@ -90,30 +90,27 @@ exp2:
add %eax,8(%esp)
f2xm1
fld1
- faddp
- fldt (%esp)
+ faddp # 2^(x-rint(x))
+ fldt (%esp) # 2^rint(x)
fmulp
fstp %st(1)
- add $12,%esp
+2: add $12,%esp
ret
-2: fld %st(0)
+3: fld %st(0)
fstpt (%esp)
- mov 9(%esp),%ah
- and $0x7f,%ah
- cmp $0x7f,%ah
- jne 1f
- decb 9(%esp)
- fstp %st(0)
- fldt (%esp)
-1: fld %st(0)
+ fld1
+ mov 8(%esp),%ax
+ and $0x7fff,%ax
+ cmp $0x7fff,%ax
+ je 1f # x = +-inf
+ fld %st(1)
frndint
- fxch %st(1)
- fsub %st(1)
+ fxch %st(2)
+ fsub %st(2) # st(0)=x-rint(x), st(1)=1, st(2)=rint(x)
f2xm1
- fld1
- faddp
- fscale
+ faddp # 2^(x-rint(x))
+1: fscale
fstp %st(1)
add $12,%esp
ret