asm for hypot and hypotf

special care is made to avoid any inexact computations when either arg
is zero (in which case the exact absolute value of the other arg
should be returned) and to support the special condition that
hypot(±inf,nan) yields inf.

hypotl is not yet implemented since avoiding overflow is nontrivial.

src/math/i386/hypot.s

+.global hypot
+.type hypot,@function
+hypot:
+	mov 8(%esp),%eax
+	mov 16(%esp),%ecx
+	add %eax,%eax
+	add %ecx,%ecx
+	and %eax,%ecx
+	cmp $0xffe00000,%ecx
+	jae 2f
+	or 4(%esp),%eax
+	jnz 1f
+	fldl 12(%esp)
+	fabs
+	ret
+1:	mov 16(%esp),%eax
+	add %eax,%eax
+	or 12(%esp),%eax
+	jnz 1f
+	fldl 4(%esp)
+	fabs
+	ret
+1:	fldl 4(%esp)
+	fld %st(0)
+	fmulp
+	fldl 12(%esp)
+	fld %st(0)
+	fmulp
+	faddp
+	fsqrt
+	ret
+2:	sub $0xffe00000,%eax
+	or 4(%esp),%eax
+	jnz 1f
+	fldl 4(%esp)
+	fabs
+	ret
+1:	mov 16(%esp),%eax
+	add %eax,%eax
+	sub $0xffe00000,%eax
+	or 12(%esp),%eax
+	fldl 12(%esp)
+	jnz 1f
+	fabs
+1:	ret

src/math/i386/hypotf.s

+.global hypotf
+.type hypotf,@function
+hypotf:
+	mov 4(%esp),%eax
+	mov 8(%esp),%ecx
+	add %eax,%eax
+	add %ecx,%ecx
+	and %eax,%ecx
+	cmp $0xff000000,%ecx
+	jae 2f
+	test %eax,%eax
+	jnz 1f
+	flds 8(%esp)
+	fabs
+	ret
+1:	mov 8(%esp),%eax
+	add %eax,%eax
+	jnz 1f
+	flds 4(%esp)
+	fabs
+	ret
+1:	flds 4(%esp)
+	fld %st(0)
+	fmulp
+	flds 8(%esp)
+	fld %st(0)
+	fmulp
+	faddp
+	fsqrt
+	ret
+2:	cmp $0xff000000,%eax
+	jnz 1f
+	flds 4(%esp)
+	fabs
+	ret
+1:	mov 8(%esp),%eax
+	add %eax,%eax
+	cmp $0xff000000,%eax
+	flds 8(%esp)
+	jnz 1f
+	fabs
+1:	ret