math: fix x86 asin, atan, exp, log1p to raise underflow

[musl] / src / math / i386 / atanf.s

diff --git a/src/math/i386/atanf.s b/src/math/i386/atanf.s
index 3cd4023..8caddef 100644 (file)
--- a/src/math/i386/atanf.s
+++ b/src/math/i386/atanf.s
@@ -2,6 +2,18 @@
 .type atanf,@function
 atanf:
        flds 4(%esp)
+       mov 4(%esp),%eax
+       add %eax,%eax
+       cmp $0x01000000,%eax
+       jb 1f
        fld1
        fpatan
        ret
+               # subnormal x, return x with underflow
+1:     fnstsw %ax
+       and $16,%ax
+       jnz 2f
+       fld %st(0)
+       fmul %st(1)
+       fstps 4(%esp)
+2:     ret