atod implementation in x86 nasm compiled from C

_atod.c

// This code is taken from StackOverflow. Code taken from StackOverflow are
// licensed under CC BY-SA 3.0. See
// https://creativecommons.org/licenses/by-sa/3.0/ for more information.
//
// Source Link: https://stackoverflow.com/a/4392789/5041327

// atod converts a string to a double.
double atod(const char *s) {
  double rez = 0, fact = 1;
  if (*s == '-') {
    s++;
    fact = -1;
  };
  for (int point_seen = 0; *s; s++) {
    if (*s == '.') {
      point_seen = 1;
      continue;
    };
    int d = *s - '0';
    if (d >= 0 && d <= 9) {
      if (point_seen)
        fact /= 10.0f;
      rez = rez * 10.0f + (double)d;
    };
  };
  return rez * fact;
};

atod.asm

; This code is taken from StackOverflow. Code taken from StackOverflow are
; licensed under CC BY-SA 3.0. See
; https://creativecommons.org/licenses/by-sa/3.0/ for more information.
;  
; Source Link: https://stackoverflow.com/a/4392789/5041327

; atod converts a string to a double.
global atod

section .text

atod:

        cmp   byte [rdi], 45
        movsd xmm1, qword [rel LC1]
        jnz   ?_001
        movsd xmm1, qword [rel LC0]
        inc   rdi
?_001:
        movsd xmm2, qword [rel LC3]
        xor   edx, edx
        xorps xmm0, xmm0
?_002:
        movsx eax, byte [rdi]
        test  al, al
        jz    ?_006
        cmp   al, 46
        jz    ?_004
        sub   eax, 48
        cmp   eax, 9
        ja    ?_005
        test  edx, edx
        jz    ?_003
        divsd xmm1, xmm2
?_003:
        mulsd    xmm0, xmm2
        cvtsi2sd xmm3, eax
        addsd    xmm0, xmm3
        jmp      ?_005

?_004:
        mov edx, 1
?_005:
        inc rdi
        jmp ?_002

?_006:

        mulsd xmm0, xmm1
        ret   

section .data

section .bss

section .rodata

LC0:
 dq 0BFF0000000000000H

LC1:
 dq 3FF0000000000000H

LC3:
 dq 4024000000000000H

Makefile

atod.asm: _atod.c
	gcc -Wall -Os -s -c ./_atod.c	
	objconv -fnasm _atod.o
	# Sanitize the output.
	dos2unix _atod.asm
	sed -i \
		-e 's/;.*$$//' \
		-e 's/\.\(LC[0-9]*\)/\1/g' \
		-e 's/^default rel//g' \
		-e 's/^SECTION \(\.\w*\).*$$/section \1/g' \
		-e 's/^global \(\w*\):.*$$/global \1/g' \
		-e 's/^section \.\(note\|eh_frame\)//g' \
		-e 's/ *\(db\|dd\) .*//g' \
		-e 's/^\([^ ]*\):\(.*\)$$/\1:\n\2/g' \
		_atod.asm
	command -v nasmfmt &> /dev/null && nasmfmt _atod.asm
	# Transfer the comments over.
	cat _atod.c \
		| sed -n '/\(\/\/\|^$$\)/p' \
		| sed -e 's/\/\//;/' -e 's/^;$$/; /g' \
		> _atod.cmt
	# Merge the comments into the assembly.
	cat _atod.cmt _atod.asm > atod.asm
	# Tidy and format.
	rm _atod.cmt _atod.asm