void put8(cp) unsigned char *cp;
{
  int i;
  for (i = 0; i < 8; i++) {
    printf("%02x", *cp++ & 0xff);
  }
}


x86 assembly (clang, -O0):
<put8>:
push   %rbp
mov    %rsp,%rbp
sub    $0x10,%rsp
mov    %rdi,-0x8(%rbp)
movl   $0x0,-0xc(%rbp)
cmpl   $0x8,-0xc(%rbp)
jge    1161 <put8+0x51>
mov    -0x8(%rbp),%rax
mov    %rax,%rcx
add    $0x1,%rcx
mov    %rcx,-0x8(%rbp)
movzbl (%rax),%esi
and    $0xff,%esi
lea    0xeb4(%rip),%rdi
mov    $0x0,%al
call   1030 <printf@plt>
mov    -0xc(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0xc(%rbp)
jmp    1123 <put8+0x13>
add    $0x10,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<put8>:
push   %r14
push   %rbx
push   %rax
mov    %rdi,%rbx
movzbl (%rdi),%esi
lea    0xedf(%rip),%r14
mov    %r14,%rdi
xor    %eax,%eax
call   1030 <printf@plt>
movzbl 0x1(%rbx),%esi
mov    %r14,%rdi
xor    %eax,%eax
call   1030 <printf@plt>
movzbl 0x2(%rbx),%esi
mov    %r14,%rdi
xor    %eax,%eax
call   1030 <printf@plt>
movzbl 0x3(%rbx),%esi
mov    %r14,%rdi
xor    %eax,%eax
call   1030 <printf@plt>
movzbl 0x4(%rbx),%esi
mov    %r14,%rdi
xor    %eax,%eax
call   1030 <printf@plt>
movzbl 0x5(%rbx),%esi
mov    %r14,%rdi
xor    %eax,%eax
call   1030 <printf@plt>
movzbl 0x6(%rbx),%esi
mov    %r14,%rdi
xor    %eax,%eax
call   1030 <printf@plt>
movzbl 0x7(%rbx),%esi
mov    %r14,%rdi
xor    %eax,%eax
add    $0x8,%rsp
pop    %rbx
pop    %r14
jmp    1030 <printf@plt>

LLVM IR (-O0):
@.str = [5 x i8] c"%02x\00"
define void @put8(i8* %0) {
%2 = alloca i8*
%3 = alloca i32
store i8* %0, i8** %2
store i32 0, i32* %3
br label %4
4: ; preds = %14, %1
%5 = load i32, i32* %3
%6 = icmp slt i32 %5, 8
br i1 %6, label %7, label %17
7: ; preds = %4
%8 = load i8*, i8** %2
%9 = getelementptr inbounds i8, i8* %8, i32 1
store i8* %9, i8** %2
%10 = load i8, i8* %8
%11 = zext i8 %10 to i32
%12 = and i32 %11, 255
%13 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i32 %12)
br label %14
14: ; preds = %7
%15 = load i32, i32* %3
%16 = add nsw i32 %15, 1
store i32 %16, i32* %3
br label %4
17: ; preds = %4
ret void
}

LLVM IR (-O2):
@.str = [5 x i8] c"%02x\00"
define void @put8(i8* nocapture %0) {
%2 = getelementptr inbounds i8, i8* %0, i64 1
%3 = load i8, i8* %0
%4 = zext i8 %3 to i32
%5 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i32 %4)
%6 = getelementptr inbounds i8, i8* %0, i64 2
%7 = load i8, i8* %2
%8 = zext i8 %7 to i32
%9 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i32 %8)
%10 = getelementptr inbounds i8, i8* %0, i64 3
%11 = load i8, i8* %6
%12 = zext i8 %11 to i32
%13 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i32 %12)
%14 = getelementptr inbounds i8, i8* %0, i64 4
%15 = load i8, i8* %10
%16 = zext i8 %15 to i32
%17 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i32 %16)
%18 = getelementptr inbounds i8, i8* %0, i64 5
%19 = load i8, i8* %14
%20 = zext i8 %19 to i32
%21 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i32 %20)
%22 = getelementptr inbounds i8, i8* %0, i64 6
%23 = load i8, i8* %18
%24 = zext i8 %23 to i32
%25 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i32 %24)
%26 = getelementptr inbounds i8, i8* %0, i64 7
%27 = load i8, i8* %22
%28 = zext i8 %27 to i32
%29 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i32 %28)
%30 = load i8, i8* %26
%31 = zext i8 %30 to i32
%32 = tail call i32 (i8*, ...) @printf(i8* dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i32 %31)
ret void
}