void tableStartATH(double atp_value, double atpH[5][5]) {
  int i, j;
  for (i = 0; i < 5; ++i) {
    for (j = 0; j < 5; ++j) {
      atpH[i][j] = 0.0;
    }
  }
  atpH[0][3] = atpH[3][0] = atp_value;
}


x86 assembly (clang, -O0):
<tableStartATH>:
push   %rbp
mov    %rsp,%rbp
movsd  %xmm0,-0x8(%rbp)
mov    %rdi,-0x10(%rbp)
movl   $0x0,-0x14(%rbp)
cmpl   $0x5,-0x14(%rbp)
jge    116b <tableStartATH+0x6b>
movl   $0x0,-0x18(%rbp)
cmpl   $0x5,-0x18(%rbp)
jge    1158 <tableStartATH+0x58>
mov    -0x10(%rbp),%rax
movslq -0x14(%rbp),%rcx
imul   $0x28,%rcx,%rcx
add    %rcx,%rax
movslq -0x18(%rbp),%rcx
xorps  %xmm0,%xmm0
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x18(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x18(%rbp)
jmp    1125 <tableStartATH+0x25>
jmp    115d <tableStartATH+0x5d>
mov    -0x14(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x14(%rbp)
jmp    1114 <tableStartATH+0x14>
movsd  -0x8(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movsd  %xmm0,0x78(%rax)
mov    -0x10(%rbp),%rax
movsd  %xmm0,0x18(%rax)
pop    %rbp
ret

x86 assembly (clang, -O2):
<tableStartATH>:
xorps  %xmm1,%xmm1
movups %xmm1,0x70(%rdi)
movups %xmm1,0x10(%rdi)
movups %xmm1,0xb0(%rdi)
movups %xmm1,0xa0(%rdi)
movups %xmm1,0x90(%rdi)
movups %xmm1,0x80(%rdi)
movups %xmm1,0x60(%rdi)
movups %xmm1,0x50(%rdi)
movups %xmm1,0x40(%rdi)
movups %xmm1,0x30(%rdi)
movups %xmm1,0x20(%rdi)
movups %xmm1,(%rdi)
movq   $0x0,0xc0(%rdi)
movsd  %xmm0,0x78(%rdi)
movsd  %xmm0,0x18(%rdi)
ret

LLVM IR (-O0):
define void @tableStartATH(double %0, [5 x double]* %1) {
%3 = alloca double
%4 = alloca [5 x double]*
%5 = alloca i32
%6 = alloca i32
store double %0, double* %3
store [5 x double]* %1, [5 x double]** %4
store i32 0, i32* %5
br label %7
7: ; preds = %26, %2
%8 = load i32, i32* %5
%9 = icmp slt i32 %8, 5
br i1 %9, label %10, label %29
10: ; preds = %7
store i32 0, i32* %6
br label %11
11: ; preds = %22, %10
%12 = load i32, i32* %6
%13 = icmp slt i32 %12, 5
br i1 %13, label %14, label %25
14: ; preds = %11
%15 = load [5 x double]*, [5 x double]** %4
%16 = load i32, i32* %5
%17 = sext i32 %16 to i64
%18 = getelementptr inbounds [5 x double], [5 x double]* %15, i64 %17
%19 = load i32, i32* %6
%20 = sext i32 %19 to i64
%21 = getelementptr inbounds [5 x double], [5 x double]* %18, i64 0, i64 %20
store double 0.000000e+00, double* %21
br label %22
22: ; preds = %14
%23 = load i32, i32* %6
%24 = add nsw i32 %23, 1
store i32 %24, i32* %6
br label %11
25: ; preds = %11
br label %26
26: ; preds = %25
%27 = load i32, i32* %5
%28 = add nsw i32 %27, 1
store i32 %28, i32* %5
br label %7
29: ; preds = %7
%30 = load double, double* %3
%31 = load [5 x double]*, [5 x double]** %4
%32 = getelementptr inbounds [5 x double], [5 x double]* %31, i64 3
%33 = getelementptr inbounds [5 x double], [5 x double]* %32, i64 0, i64 0
store double %30, double* %33
%34 = load [5 x double]*, [5 x double]** %4
%35 = getelementptr inbounds [5 x double], [5 x double]* %34, i64 0
%36 = getelementptr inbounds [5 x double], [5 x double]* %35, i64 0, i64 3
store double %30, double* %36
ret void
}

LLVM IR (-O2):
define void @tableStartATH(double %0, [5 x double]* nocapture writeonly %1) {
%3 = bitcast [5 x double]* %1 to i8*
%4 = getelementptr inbounds [5 x double], [5 x double]* %1, i64 3, i64 0
store double %0, double* %4
%5 = getelementptr inbounds [5 x double], [5 x double]* %1, i64 0, i64 3
store double %0, double* %5
ret void
}