user: Please show me the C implementation that matches the assembly code listed below:

```asm
<count_letters>:
  endbr64
  mov    %esi,%ecx
  test   %esi,%esi
  jle    L84
  lea    -0x1(%rsi),%eax
  cmp    $0xe,%eax
  jbe    L10
  movd   %edx,%xmm4
  shr    $0x4,%esi
  mov    %rdi,%rax
  pxor   %xmm1,%xmm1
  punpcklbw %xmm4,%xmm4
  pxor   %xmm6,%xmm6
  pxor   %xmm5,%xmm5
  sub    $0x1,%esi
  punpcklwd %xmm4,%xmm4
  shl    $0x4,%rsi
  movdqa D3(%rip),%xmm7
  pshufd $0x0,%xmm4,%xmm4
  lea    0x10(%rdi,%rsi,1),%rsi
  nopl   0x0(%rax)
L134:
  movdqu (%rax),%xmm0
  movdqa %xmm6,%xmm3
  add    $0x10,%rax
  pcmpeqb %xmm4,%xmm0
  pand   %xmm7,%xmm0
  pcmpgtb %xmm0,%xmm3
  movdqa %xmm0,%xmm2
  punpcklbw %xmm3,%xmm2
  punpckhbw %xmm3,%xmm0
  movdqa %xmm5,%xmm3
  pcmpgtw %xmm2,%xmm3
  movdqa %xmm2,%xmm8
  punpcklwd %xmm3,%xmm8
  punpckhwd %xmm3,%xmm2
  movdqa %xmm0,%xmm3
  paddd  %xmm8,%xmm1
  paddd  %xmm2,%xmm1
  movdqa %xmm5,%xmm2
  pcmpgtw %xmm0,%xmm2
  punpcklwd %xmm2,%xmm3
  punpckhwd %xmm2,%xmm0
  paddd  %xmm3,%xmm1
  paddd  %xmm0,%xmm1
  cmp    %rsi,%rax
  jne    L134
  movdqa %xmm1,%xmm0
  mov    %ecx,%esi
  psrldq $0x8,%xmm0
  and    $0xfffffff0,%esi
  paddd  %xmm0,%xmm1
  movdqa %xmm1,%xmm0
  psrldq $0x4,%xmm0
  paddd  %xmm0,%xmm1
  movd   %xmm1,%eax
  test   $0xf,%cl
  je     L83
L71:
  movslq %esi,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0x1(%rsi),%r8d
  cmp    %ecx,%r8d
  jge    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0x2(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0x3(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0x4(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0x5(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0x6(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0x7(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0x8(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0x9(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0xa(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0xb(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0xc(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  movzbl %r8b,%r8d
  add    %r8d,%eax
  lea    0xd(%rsi),%r8d
  cmp    %r8d,%ecx
  jle    L64
  movslq %r8d,%r8
  cmp    %dl,(%rdi,%r8,1)
  sete   %r8b
  add    $0xe,%esi
  movzbl %r8b,%r8d
  add    %r8d,%eax
  cmp    %esi,%ecx
  jle    L64
  movslq %esi,%rsi
  cmp    %dl,(%rdi,%rsi,1)
  sete   %dl
  movzbl %dl,%edx
  add    %edx,%eax
  ret
  nopw   0x0(%rax,%rax,1)
L84:
  xor    %eax,%eax
L64:
  ret
L10:
  xor    %esi,%esi
  xor    %eax,%eax
  jmp    L71
L83:
  ret
```

tool_calls: name: read_data
arguments: data_tag: D3
type_infered: byte[16]

tool: {"D3": [0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01]}

assistant: ```c
int count_letters(char str[], int str_len, char c) {
  int count = 0;
  for (int i = 0; i < str_len; ++i) {
    if (str[i] == c) {
      count++;
    }
  }
  return count;
}
```