void m_copy(double *s, double *m) {
  int j;
  for (j = 0; j < 16; j++)
    s[j] = m[j];
}


x86 assembly (clang, -O0):
<m_copy>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
movl   $0x0,-0x14(%rbp)
cmpl   $0x10,-0x14(%rbp)
jge    1145 <m_copy+0x45>
mov    -0x10(%rbp),%rax
movslq -0x14(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x8(%rbp),%rax
movslq -0x14(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x14(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x14(%rbp)
jmp    1113 <m_copy+0x13>
pop    %rbp
ret

x86 assembly (clang, -O2):
<m_copy>:
movsd  (%rsi),%xmm0
movsd  %xmm0,(%rdi)
movsd  0x8(%rsi),%xmm0
movsd  %xmm0,0x8(%rdi)
movsd  0x10(%rsi),%xmm0
movsd  %xmm0,0x10(%rdi)
movsd  0x18(%rsi),%xmm0
movsd  %xmm0,0x18(%rdi)
movsd  0x20(%rsi),%xmm0
movsd  %xmm0,0x20(%rdi)
movsd  0x28(%rsi),%xmm0
movsd  %xmm0,0x28(%rdi)
movsd  0x30(%rsi),%xmm0
movsd  %xmm0,0x30(%rdi)
movsd  0x38(%rsi),%xmm0
movsd  %xmm0,0x38(%rdi)
movsd  0x40(%rsi),%xmm0
movsd  %xmm0,0x40(%rdi)
movsd  0x48(%rsi),%xmm0
movsd  %xmm0,0x48(%rdi)
movsd  0x50(%rsi),%xmm0
movsd  %xmm0,0x50(%rdi)
movsd  0x58(%rsi),%xmm0
movsd  %xmm0,0x58(%rdi)
movsd  0x60(%rsi),%xmm0
movsd  %xmm0,0x60(%rdi)
movsd  0x68(%rsi),%xmm0
movsd  %xmm0,0x68(%rdi)
movsd  0x70(%rsi),%xmm0
movsd  %xmm0,0x70(%rdi)
movsd  0x78(%rsi),%xmm0
movsd  %xmm0,0x78(%rdi)
ret

LLVM IR (-O0):
define void @m_copy(double* %0, double* %1) {
%3 = alloca double*
%4 = alloca double*
%5 = alloca i32
store double* %0, double** %3
store double* %1, double** %4
store i32 0, i32* %5
br label %6
6: ; preds = %19, %2
%7 = load i32, i32* %5
%8 = icmp slt i32 %7, 16
br i1 %8, label %9, label %22
9: ; preds = %6
%10 = load double*, double** %4
%11 = load i32, i32* %5
%12 = sext i32 %11 to i64
%13 = getelementptr inbounds double, double* %10, i64 %12
%14 = load double, double* %13
%15 = load double*, double** %3
%16 = load i32, i32* %5
%17 = sext i32 %16 to i64
%18 = getelementptr inbounds double, double* %15, i64 %17
store double %14, double* %18
br label %19
19: ; preds = %9
%20 = load i32, i32* %5
%21 = add nsw i32 %20, 1
store i32 %21, i32* %5
br label %6
22: ; preds = %6
ret void
}

LLVM IR (-O2):
define void @m_copy(double* nocapture writeonly %0, double* nocapture %1) {
%3 = load double, double* %1
store double %3, double* %0
%4 = getelementptr inbounds double, double* %1, i64 1
%5 = load double, double* %4
%6 = getelementptr inbounds double, double* %0, i64 1
store double %5, double* %6
%7 = getelementptr inbounds double, double* %1, i64 2
%8 = load double, double* %7
%9 = getelementptr inbounds double, double* %0, i64 2
store double %8, double* %9
%10 = getelementptr inbounds double, double* %1, i64 3
%11 = load double, double* %10
%12 = getelementptr inbounds double, double* %0, i64 3
store double %11, double* %12
%13 = getelementptr inbounds double, double* %1, i64 4
%14 = load double, double* %13
%15 = getelementptr inbounds double, double* %0, i64 4
store double %14, double* %15
%16 = getelementptr inbounds double, double* %1, i64 5
%17 = load double, double* %16
%18 = getelementptr inbounds double, double* %0, i64 5
store double %17, double* %18
%19 = getelementptr inbounds double, double* %1, i64 6
%20 = load double, double* %19
%21 = getelementptr inbounds double, double* %0, i64 6
store double %20, double* %21
%22 = getelementptr inbounds double, double* %1, i64 7
%23 = load double, double* %22
%24 = getelementptr inbounds double, double* %0, i64 7
store double %23, double* %24
%25 = getelementptr inbounds double, double* %1, i64 8
%26 = load double, double* %25
%27 = getelementptr inbounds double, double* %0, i64 8
store double %26, double* %27
%28 = getelementptr inbounds double, double* %1, i64 9
%29 = load double, double* %28
%30 = getelementptr inbounds double, double* %0, i64 9
store double %29, double* %30
%31 = getelementptr inbounds double, double* %1, i64 10
%32 = load double, double* %31
%33 = getelementptr inbounds double, double* %0, i64 10
store double %32, double* %33
%34 = getelementptr inbounds double, double* %1, i64 11
%35 = load double, double* %34
%36 = getelementptr inbounds double, double* %0, i64 11
store double %35, double* %36
%37 = getelementptr inbounds double, double* %1, i64 12
%38 = load double, double* %37
%39 = getelementptr inbounds double, double* %0, i64 12
store double %38, double* %39
%40 = getelementptr inbounds double, double* %1, i64 13
%41 = load double, double* %40
%42 = getelementptr inbounds double, double* %0, i64 13
store double %41, double* %42
%43 = getelementptr inbounds double, double* %1, i64 14
%44 = load double, double* %43
%45 = getelementptr inbounds double, double* %0, i64 14
store double %44, double* %45
%46 = getelementptr inbounds double, double* %1, i64 15
%47 = load double, double* %46
%48 = getelementptr inbounds double, double* %0, i64 15
store double %47, double* %48
ret void
}