X86_32 before:
00000000 <bitrev32>:
0: 55 push %ebp
1: 89 c1 mov %eax,%ecx
3: 89 e5 mov %esp,%ebp
5: 0f b6 cd movzbl %ch,%ecx
8: 53 push %ebx
9: 89 c3 mov %eax,%ebx
b: 0f b6 c0 movzbl %al,%eax
e: 0f b6 90 00 00 00 00 movzbl 0x0(%eax),%edx
15: c1 eb 10 shr $0x10,%ebx
18: 66 0f b6 81 00 00 00 movzbw 0x0(%ecx),%ax
1f: 00
20: c1 e2 08 shl $0x8,%edx
23: 09 d0 or %edx,%eax
25: 0f b6 d3 movzbl %bl,%edx
28: 0f b6 8a 00 00 00 00 movzbl 0x0(%edx),%ecx
2f: 0f b6 d7 movzbl %bh,%edx
32: 66 0f b6 92 00 00 00 movzbw 0x0(%edx),%dx
39: 00
3a: c1 e0 10 shl $0x10,%eax
3d: 5b pop %ebx
3e: 5d pop %ebp
3f: c1 e1 08 shl $0x8,%ecx
42: 09 ca or %ecx,%edx
44: 0f b7 d2 movzwl %dx,%edx
47: 09 d0 or %edx,%eax
49: c3 ret
X86_32 after:
00000000 <bitrev32>:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: 83 ec 08 sub $0x8,%esp
6: 89 45 f8 mov %eax,-0x8(%ebp)
9: 0f b6 45 f8 movzbl -0x8(%ebp),%eax
d: 8a 80 00 00 00 00 mov 0x0(%eax),%al
13: 88 45 ff mov %al,-0x1(%ebp)
16: 0f b6 45 f9 movzbl -0x7(%ebp),%eax
1a: 8a 80 00 00 00 00 mov 0x0(%eax),%al
20: 88 45 fe mov %al,-0x2(%ebp)
23: 0f b6 45 fa movzbl -0x6(%ebp),%eax
27: 8a 80 00 00 00 00 mov 0x0(%eax),%al
2d: 88 45 fd mov %al,-0x3(%ebp)
30: 0f b6 45 fb movzbl -0x5(%ebp),%eax
34: 8a 80 00 00 00 00 mov 0x0(%eax),%al
3a: 88 45 fc mov %al,-0x4...