user: 请从给定的汇编指令推导出C源代码:

```asm
<diagMul>:
  endbr64
  push   %r15
  push   %r14
  mov    %rdx,%r14
  push   %r13
  push   %r12
  push   %rbp
  mov    %edi,%ebp
  push   %rbx
  mov    %rsi,%rbx
  sub    $0x28,%rsp
  call   <sqrt@plt>
  mov    %ebp,%edi
  mov    %eax,%r15d
  mov    %eax,0xc(%rsp)
  call   <sqrt@plt>
  test   %r15d,%r15d
  jle    L219
  lea    -0x1(%rax),%ecx
  mov    %eax,%edi
  test   %ecx,%ecx
  jg     L92
  xor    %esi,%esi
L216:
  mov    %esi,%r8d
  movslq 0xc(%rsp),%rax
  imul   %edi,%r8d
  mov    %rax,0x10(%rsp)
  lea    -0x1(%rax),%r12d
  mov    %r8d,%r13d
  sub    %edi,%r13d
L159:
  movslq %r8d,%r10
  shl    $0x2,%r10
  test   %esi,%esi
  je     L17
  movslq %r13d,%rax
  lea    (%r14,%r10,1),%rdx
  lea    0x1(%r8),%r15d
  add    %rbx,%r10
  lea    (%rbx,%rax,4),%rbp
  xor    %eax,%eax
  jmp    L147
  nopl   (%rax)
L112:
  movss  (%rdx),%xmm0
  subss  (%r10,%rax,4),%xmm0
  add    $0x1,%rax
  movss  %xmm0,(%rdx)
L147:
  cmp    %eax,%ecx
  jle    L203
  lea    (%r8,%rax,1),%r9d
  lea    (%r15,%rax,1),%r11d
  movslq %r9d,%r9
  movslq %r11d,%r11
  lea    (%r14,%r9,4),%r9
  movss  (%r9),%xmm0
  subss  (%rbx,%r11,4),%xmm0
  movss  %xmm0,(%r9)
L203:
  movss  (%rdx),%xmm0
  subss  0x0(%rbp,%rax,4),%xmm0
  add    $0x4,%rdx
  movss  %xmm0,-0x4(%rdx)
  cmp    %rax,%r12
  jne    L112
  add    $0x1,%esi
  add    %edi,%r8d
  add    %edi,%r13d
  cmp    %esi,0xc(%rsp)
  jg     L159
L219:
  add    $0x28,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopw   0x0(%rax,%rax,1)
L17:
  lea    (%r14,%r10,1),%r9
  mov    0x10(%rsp),%rdx
  add    %rbx,%r10
  xor    %eax,%eax
  lea    0x1(%r8),%ebp
  jmp    L150
  nopl   0x0(%rax)
L22:
  movss  (%r9,%rax,4),%xmm0
  subss  -0x4(%r10,%rax,4),%xmm0
  movss  %xmm0,(%r9,%rax,4)
L150:
  cmp    %eax,%ecx
  jle    L15
  lea    (%r8,%rax,1),%r11d
  lea    0x0(%rbp,%rax,1),%r15d
  movslq %r11d,%r11
  movslq %r15d,%r15
  lea    (%r14,%r11,4),%r11
  movss  (%r11),%xmm0
  subss  (%rbx,%r15,4),%xmm0
  movss  %xmm0,(%r11)
L15:
  add    $0x1,%rax
  cmp    %rdx,%rax
  jne    L22
  add    $0x1,%esi
  add    %edi,%r8d
  add    %edi,%r13d
  cmp    %esi,0xc(%rsp)
  jg     L159
  jmp    L219
  nopl   0x0(%rax,%rax,1)
L92:
  mov    0xc(%rsp),%eax
  mov    %edi,%r15d
  cmp    %ecx,%eax
  mov    %eax,%esi
  lea    -0x1(%rax),%r11d
  cmovg  %ecx,%esi
  xor    %r9d,%r9d
  mov    %esi,0x18(%rsp)
  mov    %edi,%esi
  neg    %esi
  mov    %esi,0x10(%rsp)
  xor    %esi,%esi
  nopl   0x0(%rax,%rax,1)
L124:
  movslq %r9d,%r10
  shl    $0x2,%r10
  lea    (%r14,%r10,1),%rdx
  test   %esi,%esi
  je     L32
  movslq 0x10(%rsp),%rax
  lea    0x1(%r9),%r8d
  mov    %esi,0x1c(%rsp)
  add    %rbx,%r10
  mov    %r8d,%esi
  lea    (%rbx,%rax,4),%r13
  movslq %r15d,%rax
  lea    (%rbx,%rax,4),%r12
  xor    %eax,%eax
  jmp    L80
  nopl   (%rax)
L149:
  movss  (%rdx),%xmm0
  subss  (%r10,%rax,4),%xmm0
  add    $0x1,%rax
  movss  %xmm0,(%rdx)
L80:
  cmp    %eax,%ecx
  jle    L126
  lea    (%r9,%rax,1),%r8d
  movslq %r8d,%r8
  lea    (%r14,%r8,4),%rbp
  lea    (%rsi,%rax,1),%r8d
  movslq %r8d,%r8
  movss  0x0(%rbp),%xmm0
  subss  (%rbx,%r8,4),%xmm0
  movss  %xmm0,0x0(%rbp)
L126:
  movss  (%rdx),%xmm0
  subss  0x0(%r13,%rax,4),%xmm0
  add    $0x4,%rdx
  movss  %xmm0,-0x4(%rdx)
  subss  (%r12,%rax,4),%xmm0
  movss  %xmm0,-0x4(%rdx)
  cmp    %rax,%r11
  jne    L149
  mov    0x1c(%rsp),%esi
L101:
  add    %edi,0x10(%rsp)
  add    $0x1,%esi
  add    %edi,%r9d
  add    %edi,%r15d
  cmp    0x18(%rsp),%esi
  jl     L124
  cmp    %esi,0xc(%rsp)
  jg     L216
  add    $0x28,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax,%rax,1)
L32:
  movslq %r15d,%rax
  add    %rbx,%r10
  lea    0x1(%r9),%r13d
  lea    (%rbx,%rax,4),%r12
  xor    %eax,%eax
  jmp    L191
  nopw   0x0(%rax,%rax,1)
L158:
  movss  (%rdx),%xmm0
  subss  (%r10,%rax,4),%xmm0
  add    $0x1,%rax
  movss  %xmm0,(%rdx)
L191:
  cmp    %eax,%ecx
  jle    L133
  lea    (%r9,%rax,1),%r8d
  lea    0x0(%r13,%rax,1),%ebp
  movslq %r8d,%r8
  movslq %ebp,%rbp
  lea    (%r14,%r8,4),%r8
  movss  (%r8),%xmm0
  subss  (%rbx,%rbp,4),%xmm0
  movss  %xmm0,(%r8)
L133:
  movss  (%rdx),%xmm0
  subss  (%r12,%rax,4),%xmm0
  add    $0x4,%rdx
  movss  %xmm0,-0x4(%rdx)
  cmp    %rax,%r11
  jne    L158
  jmp    L101
```

assistant: ```c
void diagMul(int size, float *xx, float *res) {
  int dim = sqrt(size);
  int _xRes = sqrt(size);
  int y;
  int x;
  for (y = 0; y < dim; y++) {
    for (x = 0; x < dim; x++) {
      if (x > 0) {
        res[x + y * _xRes] += -xx[(x - 1) + y * _xRes];
      }
      if (x < _xRes - 1) {
        res[x + y * _xRes] += -xx[(x + 1) + y * _xRes];
      }
      if (y > 0) {
        res[x + y * _xRes] += -xx[x + (y - 1) * _xRes];
      }
      if (y < _xRes - 1) {
        res[x + y * _xRes] += -xx[x + (y + 1) * _xRes];
      }
    }
  }
}
```