void cftfsub(int n, double *a, double *w) {
  void cft1st(int n, double *a, double *w);
  void cftmdl(int n, int l, double *a, double *w);
  int j, j1, j2, j3, l;
  double x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;
  l = 2;
  if (n >= 16) {
    cft1st(n, a, w);
    l = 16;
    while ((l << 3) <= n) {
      cftmdl(n, l, a, w);
      l <<= 3;
    }
  }
  if ((l << 1) < n) {
    for (j = 0; j < l; j += 2) {
      j1 = j + l;
      j2 = j1 + l;
      j3 = j2 + l;
      x0r = a[j] + a[j1];
      x0i = a[j + 1] + a[j1 + 1];
      x1r = a[j] - a[j1];
      x1i = a[j + 1] - a[j1 + 1];
      x2r = a[j2] + a[j3];
      x2i = a[j2 + 1] + a[j3 + 1];
      x3r = a[j2] - a[j3];
      x3i = a[j2 + 1] - a[j3 + 1];
      a[j] = x0r + x2r;
      a[j + 1] = x0i + x2i;
      a[j2] = x0r - x2r;
      a[j2 + 1] = x0i - x2i;
      a[j1] = x1r - x3i;
      a[j1 + 1] = x1i + x3r;
      a[j3] = x1r + x3i;
      a[j3 + 1] = x1i - x3r;
    }
  } else if ((l << 1) == n) {
    for (j = 0; j < l; j += 2) {
      j1 = j + l;
      x0r = a[j] - a[j1];
      x0i = a[j + 1] - a[j1 + 1];
      a[j] += a[j1];
      a[j + 1] += a[j1 + 1];
      a[j1] = x0r;
      a[j1 + 1] = x0i;
    }
  }
}


x86 assembly (clang, -O0):
<cftfsub>:
push   %rbp
mov    %rsp,%rbp
sub    $0x70,%rsp
mov    %edi,-0x4(%rbp)
mov    %rsi,-0x10(%rbp)
mov    %rdx,-0x18(%rbp)
movl   $0x2,-0x2c(%rbp)
cmpl   $0x10,-0x4(%rbp)
jl     1190 <cftfsub+0x70>
mov    -0x4(%rbp),%edi
mov    -0x10(%rbp),%rsi
mov    -0x18(%rbp),%rdx
call   1030 <cft1st@plt>
movl   $0x10,-0x2c(%rbp)
mov    -0x2c(%rbp),%eax
shl    $0x3,%eax
cmp    -0x4(%rbp),%eax
jg     118b <cftfsub+0x6b>
mov    -0x4(%rbp),%edi
mov    -0x2c(%rbp),%esi
mov    -0x10(%rbp),%rdx
mov    -0x18(%rbp),%rcx
call   1040 <cftmdl@plt>
mov    -0x2c(%rbp),%eax
shl    $0x3,%eax
mov    %eax,-0x2c(%rbp)
jmp    115b <cftfsub+0x3b>
jmp    1190 <cftfsub+0x70>
mov    -0x2c(%rbp),%eax
shl    $0x1,%eax
cmp    -0x4(%rbp),%eax
jge    13cc <cftfsub+0x2ac>
movl   $0x0,-0x1c(%rbp)
mov    -0x1c(%rbp),%eax
cmp    -0x2c(%rbp),%eax
jge    13c7 <cftfsub+0x2a7>
mov    -0x1c(%rbp),%eax
add    -0x2c(%rbp),%eax
mov    %eax,-0x20(%rbp)
mov    -0x20(%rbp),%eax
add    -0x2c(%rbp),%eax
mov    %eax,-0x24(%rbp)
mov    -0x24(%rbp),%eax
add    -0x2c(%rbp),%eax
mov    %eax,-0x28(%rbp)
mov    -0x10(%rbp),%rax
movslq -0x1c(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x20(%rbp),%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x38(%rbp)
mov    -0x10(%rbp),%rax
mov    -0x1c(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x20(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x40(%rbp)
mov    -0x10(%rbp),%rax
movslq -0x1c(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x20(%rbp),%rcx
subsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x48(%rbp)
mov    -0x10(%rbp),%rax
mov    -0x1c(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x20(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
subsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x50(%rbp)
mov    -0x10(%rbp),%rax
movslq -0x24(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x28(%rbp),%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x58(%rbp)
mov    -0x10(%rbp),%rax
mov    -0x24(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x28(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x60(%rbp)
mov    -0x10(%rbp),%rax
movslq -0x24(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x28(%rbp),%rcx
subsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x68(%rbp)
mov    -0x10(%rbp),%rax
mov    -0x24(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x28(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
subsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x70(%rbp)
movsd  -0x38(%rbp),%xmm0
addsd  -0x58(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x1c(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x40(%rbp),%xmm0
addsd  -0x60(%rbp),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x1c(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x38(%rbp),%xmm0
subsd  -0x58(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x24(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x40(%rbp),%xmm0
subsd  -0x60(%rbp),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x24(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x48(%rbp),%xmm0
subsd  -0x70(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x20(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x50(%rbp),%xmm0
addsd  -0x68(%rbp),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x20(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x48(%rbp),%xmm0
addsd  -0x70(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x28(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x50(%rbp),%xmm0
subsd  -0x68(%rbp),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x28(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x1c(%rbp),%eax
add    $0x2,%eax
mov    %eax,-0x1c(%rbp)
jmp    11a6 <cftfsub+0x86>
jmp    14c8 <cftfsub+0x3a8>
mov    -0x2c(%rbp),%eax
shl    $0x1,%eax
cmp    -0x4(%rbp),%eax
jne    14c3 <cftfsub+0x3a3>
movl   $0x0,-0x1c(%rbp)
mov    -0x1c(%rbp),%eax
cmp    -0x2c(%rbp),%eax
jge    14be <cftfsub+0x39e>
mov    -0x1c(%rbp),%eax
add    -0x2c(%rbp),%eax
mov    %eax,-0x20(%rbp)
mov    -0x10(%rbp),%rax
movslq -0x1c(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x20(%rbp),%rcx
subsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x38(%rbp)
mov    -0x10(%rbp),%rax
mov    -0x1c(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x20(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
subsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x40(%rbp)
mov    -0x10(%rbp),%rax
movslq -0x20(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x1c(%rbp),%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x10(%rbp),%rax
mov    -0x20(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x1c(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x38(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x20(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x40(%rbp),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x20(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x1c(%rbp),%eax
add    $0x2,%eax
mov    %eax,-0x1c(%rbp)
jmp    13e2 <cftfsub+0x2c2>
jmp    14c3 <cftfsub+0x3a3>
jmp    14c8 <cftfsub+0x3a8>
add    $0x70,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<cftfsub>:
push   %rbp
push   %r15
push   %r14
push   %rbx
push   %rax
mov    %rsi,%rbx
mov    %edi,%r15d
mov    $0x2,%ebp
cmp    $0x10,%edi
jl     117e <cftfsub+0x5e>
mov    %rdx,%r14
mov    %r15d,%edi
mov    %rbx,%rsi
call   1030 <cft1st@plt>
mov    $0x10,%ebp
cmp    $0x80,%r15d
jb     117e <cftfsub+0x5e>
mov    $0x10,%esi
mov    $0x80,%eax
nopl   (%rax)
mov    %eax,%ebp
mov    %r15d,%edi
mov    %rbx,%rdx
mov    %r14,%rcx
call   1040 <cftmdl@plt>
lea    0x0(,%rbp,8),%eax
mov    %ebp,%esi
cmp    %r15d,%eax
jle    1160 <cftfsub+0x40>
lea    0x0(%rbp,%rbp,1),%r9d
cmp    %r15d,%r9d
jge    12a2 <cftfsub+0x182>
test   %ebp,%ebp
jle    131d <cftfsub+0x1fd>
movabs $0x200000000,%r8
mov    %ebp,%r10d
or     $0x1,%r9
mov    %r10,%rdi
shl    $0x20,%rdi
lea    (%rbx,%r10,8),%r11
lea    (%rdi,%rdi,2),%rcx
lea    (%r10,%r10,2),%rax
lea    (%rbx,%rax,8),%r14
mov    %r10,%r15
shl    $0x4,%r15
add    %rbx,%r15
xor    %eax,%eax
nopl   0x0(%rax,%rax,1)
movsd  (%r11,%rax,8),%xmm2
movupd (%rbx,%rax,8),%xmm0
mov    %rdi,%rsi
sar    $0x1d,%rsi
or     $0x8,%rsi
movsd  (%rbx,%rsi,1),%xmm3
movapd %xmm0,%xmm1
subsd  %xmm2,%xmm1
unpcklpd %xmm3,%xmm2
addpd  %xmm0,%xmm2
unpckhpd %xmm0,%xmm0
subsd  %xmm3,%xmm0
movsd  (%r15,%rax,8),%xmm3
movsd  (%r14,%rax,8),%xmm4
lea    (%r9,%rax,1),%ebp
movslq %ebp,%rdx
movsd  (%rbx,%rdx,8),%xmm5
mov    %rcx,%rbp
sar    $0x1d,%rbp
or     $0x8,%rbp
movsd  (%rbx,%rbp,1),%xmm6
movapd %xmm3,%xmm7
unpcklpd %xmm5,%xmm7
subsd  %xmm4,%xmm3
unpcklpd %xmm6,%xmm4
addpd  %xmm7,%xmm4
subsd  %xmm6,%xmm5
movapd %xmm2,%xmm6
addpd  %xmm4,%xmm6
movupd %xmm6,(%rbx,%rax,8)
subpd  %xmm4,%xmm2
movlpd %xmm2,(%r15,%rax,8)
movhpd %xmm2,(%rbx,%rdx,8)
movapd %xmm1,%xmm2
subsd  %xmm5,%xmm2
movsd  %xmm2,(%r11,%rax,8)
movapd %xmm0,%xmm2
addsd  %xmm3,%xmm2
movsd  %xmm2,(%rbx,%rsi,1)
addsd  %xmm1,%xmm5
movsd  %xmm5,(%r14,%rax,8)
subsd  %xmm3,%xmm0
movsd  %xmm0,(%rbx,%rbp,1)
add    $0x2,%rax
add    %r8,%rdi
add    %r8,%rcx
cmp    %r10,%rax
jb     11d0 <cftfsub+0xb0>
jmp    131d <cftfsub+0x1fd>
jne    131d <cftfsub+0x1fd>
test   %ebp,%ebp
jle    131d <cftfsub+0x1fd>
movabs $0x200000000,%rax
mov    %ebp,%ebp
mov    %rbp,%rcx
shl    $0x20,%rcx
lea    (%rbx,%rbp,8),%rsi
xor    %edi,%edi
cs nopw 0x0(%rax,%rax,1)
nopl   0x0(%rax,%rax,1)
movsd  (%rsi,%rdi,8),%xmm0
movupd (%rbx,%rdi,8),%xmm1
movapd %xmm1,%xmm2
subsd  %xmm0,%xmm2
mov    %rcx,%rdx
sar    $0x1d,%rdx
or     $0x8,%rdx
movsd  (%rbx,%rdx,1),%xmm3
unpcklpd %xmm3,%xmm0
addpd  %xmm1,%xmm0
unpckhpd %xmm1,%xmm1
subsd  %xmm3,%xmm1
movupd %xmm0,(%rbx,%rdi,8)
movsd  %xmm2,(%rsi,%rdi,8)
movsd  %xmm1,(%rbx,%rdx,1)
add    $0x2,%rdi
add    %rax,%rcx
cmp    %rbp,%rdi
jb     12d0 <cftfsub+0x1b0>
add    $0x8,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
ret

LLVM IR (-O0):
define void @cftfsub(i32 %0, double* %1, double* %2) {
%4 = alloca i32
%5 = alloca double*
%6 = alloca double*
%7 = alloca i32
%8 = alloca i32
%9 = alloca i32
%10 = alloca i32
%11 = alloca i32
%12 = alloca double
%13 = alloca double
%14 = alloca double
%15 = alloca double
%16 = alloca double
%17 = alloca double
%18 = alloca double
%19 = alloca double
store i32 %0, i32* %4
store double* %1, double** %5
store double* %2, double** %6
store i32 2, i32* %11
%20 = load i32, i32* %4
%21 = icmp sge i32 %20, 16
br i1 %21, label %22, label %39
22: ; preds = %3
%23 = load i32, i32* %4
%24 = load double*, double** %5
%25 = load double*, double** %6
store i32 16, i32* %11
br label %26
26: ; preds = %31, %22
%27 = load i32, i32* %11
%28 = shl i32 %27, 3
%29 = load i32, i32* %4
%30 = icmp sle i32 %28, %29
br i1 %30, label %31, label %38
31: ; preds = %26
%32 = load i32, i32* %4
%33 = load i32, i32* %11
%34 = load double*, double** %5
%35 = load double*, double** %6
%36 = load i32, i32* %11
%37 = shl i32 %36, 3
store i32 %37, i32* %11
br label %26
38: ; preds = %26
br label %39
39: ; preds = %38, %3
%40 = load i32, i32* %11
%41 = shl i32 %40, 1
%42 = load i32, i32* %4
%43 = icmp slt i32 %41, %42
br i1 %43, label %44, label %219
44: ; preds = %39
store i32 0, i32* %7
br label %45
45: ; preds = %215, %44
%46 = load i32, i32* %7
%47 = load i32, i32* %11
%48 = icmp slt i32 %46, %47
br i1 %48, label %49, label %218
49: ; preds = %45
%50 = load i32, i32* %7
%51 = load i32, i32* %11
%52 = add nsw i32 %50, %51
store i32 %52, i32* %8
%53 = load i32, i32* %8
%54 = load i32, i32* %11
%55 = add nsw i32 %53, %54
store i32 %55, i32* %9
%56 = load i32, i32* %9
%57 = load i32, i32* %11
%58 = add nsw i32 %56, %57
store i32 %58, i32* %10
%59 = load double*, double** %5
%60 = load i32, i32* %7
%61 = sext i32 %60 to i64
%62 = getelementptr inbounds double, double* %59, i64 %61
%63 = load double, double* %62
%64 = load double*, double** %5
%65 = load i32, i32* %8
%66 = sext i32 %65 to i64
%67 = getelementptr inbounds double, double* %64, i64 %66
%68 = load double, double* %67
%69 = fadd double %63, %68
store double %69, double* %12
%70 = load double*, double** %5
%71 = load i32, i32* %7
%72 = add nsw i32 %71, 1
%73 = sext i32 %72 to i64
%74 = getelementptr inbounds double, double* %70, i64 %73
%75 = load double, double* %74
%76 = load double*, double** %5
%77 = load i32, i32* %8
%78 = add nsw i32 %77, 1
%79 = sext i32 %78 to i64
%80 = getelementptr inbounds double, double* %76, i64 %79
%81 = load double, double* %80
%82 = fadd double %75, %81
store double %82, double* %13
%83 = load double*, double** %5
%84 = load i32, i32* %7
%85 = sext i32 %84 to i64
%86 = getelementptr inbounds double, double* %83, i64 %85
%87 = load double, double* %86
%88 = load double*, double** %5
%89 = load i32, i32* %8
%90 = sext i32 %89 to i64
%91 = getelementptr inbounds double, double* %88, i64 %90
%92 = load double, double* %91
%93 = fsub double %87, %92
store double %93, double* %14
%94 = load double*, double** %5
%95 = load i32, i32* %7
%96 = add nsw i32 %95, 1
%97 = sext i32 %96 to i64
%98 = getelementptr inbounds double, double* %94, i64 %97
%99 = load double, double* %98
%100 = load double*, double** %5
%101 = load i32, i32* %8
%102 = add nsw i32 %101, 1
%103 = sext i32 %102 to i64
%104 = getelementptr inbounds double, double* %100, i64 %103
%105 = load double, double* %104
%106 = fsub double %99, %105
store double %106, double* %15
%107 = load double*, double** %5
%108 = load i32, i32* %9
%109 = sext i32 %108 to i64
%110 = getelementptr inbounds double, double* %107, i64 %109
%111 = load double, double* %110
%112 = load double*, double** %5
%113 = load i32, i32* %10
%114 = sext i32 %113 to i64
%115 = getelementptr inbounds double, double* %112, i64 %114
%116 = load double, double* %115
%117 = fadd double %111, %116
store double %117, double* %16
%118 = load double*, double** %5
%119 = load i32, i32* %9
%120 = add nsw i32 %119, 1
%121 = sext i32 %120 to i64
%122 = getelementptr inbounds double, double* %118, i64 %121
%123 = load double, double* %122
%124 = load double*, double** %5
%125 = load i32, i32* %10
%126 = add nsw i32 %125, 1
%127 = sext i32 %126 to i64
%128 = getelementptr inbounds double, double* %124, i64 %127
%129 = load double, double* %128
%130 = fadd double %123, %129
store double %130, double* %17
%131 = load double*, double** %5
%132 = load i32, i32* %9
%133 = sext i32 %132 to i64
%134 = getelementptr inbounds double, double* %131, i64 %133
%135 = load double, double* %134
%136 = load double*, double** %5
%137 = load i32, i32* %10
%138 = sext i32 %137 to i64
%139 = getelementptr inbounds double, double* %136, i64 %138
%140 = load double, double* %139
%141 = fsub double %135, %140
store double %141, double* %18
%142 = load double*, double** %5
%143 = load i32, i32* %9
%144 = add nsw i32 %143, 1
%145 = sext i32 %144 to i64
%146 = getelementptr inbounds double, double* %142, i64 %145
%147 = load double, double* %146
%148 = load double*, double** %5
%149 = load i32, i32* %10
%150 = add nsw i32 %149, 1
%151 = sext i32 %150 to i64
%152 = getelementptr inbounds double, double* %148, i64 %151
%153 = load double, double* %152
%154 = fsub double %147, %153
store double %154, double* %19
%155 = load double, double* %12
%156 = load double, double* %16
%157 = fadd double %155, %156
%158 = load double*, double** %5
%159 = load i32, i32* %7
%160 = sext i32 %159 to i64
%161 = getelementptr inbounds double, double* %158, i64 %160
store double %157, double* %161
%162 = load double, double* %13
%163 = load double, double* %17
%164 = fadd double %162, %163
%165 = load double*, double** %5
%166 = load i32, i32* %7
%167 = add nsw i32 %166, 1
%168 = sext i32 %167 to i64
%169 = getelementptr inbounds double, double* %165, i64 %168
store double %164, double* %169
%170 = load double, double* %12
%171 = load double, double* %16
%172 = fsub double %170, %171
%173 = load double*, double** %5
%174 = load i32, i32* %9
%175 = sext i32 %174 to i64
%176 = getelementptr inbounds double, double* %173, i64 %175
store double %172, double* %176
%177 = load double, double* %13
%178 = load double, double* %17
%179 = fsub double %177, %178
%180 = load double*, double** %5
%181 = load i32, i32* %9
%182 = add nsw i32 %181, 1
%183 = sext i32 %182 to i64
%184 = getelementptr inbounds double, double* %180, i64 %183
store double %179, double* %184
%185 = load double, double* %14
%186 = load double, double* %19
%187 = fsub double %185, %186
%188 = load double*, double** %5
%189 = load i32, i32* %8
%190 = sext i32 %189 to i64
%191 = getelementptr inbounds double, double* %188, i64 %190
store double %187, double* %191
%192 = load double, double* %15
%193 = load double, double* %18
%194 = fadd double %192, %193
%195 = load double*, double** %5
%196 = load i32, i32* %8
%197 = add nsw i32 %196, 1
%198 = sext i32 %197 to i64
%199 = getelementptr inbounds double, double* %195, i64 %198
store double %194, double* %199
%200 = load double, double* %14
%201 = load double, double* %19
%202 = fadd double %200, %201
%203 = load double*, double** %5
%204 = load i32, i32* %10
%205 = sext i32 %204 to i64
%206 = getelementptr inbounds double, double* %203, i64 %205
store double %202, double* %206
%207 = load double, double* %15
%208 = load double, double* %18
%209 = fsub double %207, %208
%210 = load double*, double** %5
%211 = load i32, i32* %10
%212 = add nsw i32 %211, 1
%213 = sext i32 %212 to i64
%214 = getelementptr inbounds double, double* %210, i64 %213
store double %209, double* %214
br label %215
215: ; preds = %49
%216 = load i32, i32* %7
%217 = add nsw i32 %216, 2
store i32 %217, i32* %7
br label %45
218: ; preds = %45
br label %297
219: ; preds = %39
%220 = load i32, i32* %11
%221 = shl i32 %220, 1
%222 = load i32, i32* %4
%223 = icmp eq i32 %221, %222
br i1 %223, label %224, label %296
224: ; preds = %219
store i32 0, i32* %7
br label %225
225: ; preds = %292, %224
%226 = load i32, i32* %7
%227 = load i32, i32* %11
%228 = icmp slt i32 %226, %227
br i1 %228, label %229, label %295
229: ; preds = %225
%230 = load i32, i32* %7
%231 = load i32, i32* %11
%232 = add nsw i32 %230, %231
store i32 %232, i32* %8
%233 = load double*, double** %5
%234 = load i32, i32* %7
%235 = sext i32 %234 to i64
%236 = getelementptr inbounds double, double* %233, i64 %235
%237 = load double, double* %236
%238 = load double*, double** %5
%239 = load i32, i32* %8
%240 = sext i32 %239 to i64
%241 = getelementptr inbounds double, double* %238, i64 %240
%242 = load double, double* %241
%243 = fsub double %237, %242
store double %243, double* %12
%244 = load double*, double** %5
%245 = load i32, i32* %7
%246 = add nsw i32 %245, 1
%247 = sext i32 %246 to i64
%248 = getelementptr inbounds double, double* %244, i64 %247
%249 = load double, double* %248
%250 = load double*, double** %5
%251 = load i32, i32* %8
%252 = add nsw i32 %251, 1
%253 = sext i32 %252 to i64
%254 = getelementptr inbounds double, double* %250, i64 %253
%255 = load double, double* %254
%256 = fsub double %249, %255
store double %256, double* %13
%257 = load double*, double** %5
%258 = load i32, i32* %8
%259 = sext i32 %258 to i64
%260 = getelementptr inbounds double, double* %257, i64 %259
%261 = load double, double* %260
%262 = load double*, double** %5
%263 = load i32, i32* %7
%264 = sext i32 %263 to i64
%265 = getelementptr inbounds double, double* %262, i64 %264
%266 = load double, double* %265
%267 = fadd double %266, %261
store double %267, double* %265
%268 = load double*, double** %5
%269 = load i32, i32* %8
%270 = add nsw i32 %269, 1
%271 = sext i32 %270 to i64
%272 = getelementptr inbounds double, double* %268, i64 %271
%273 = load double, double* %272
%274 = load double*, double** %5
%275 = load i32, i32* %7
%276 = add nsw i32 %275, 1
%277 = sext i32 %276 to i64
%278 = getelementptr inbounds double, double* %274, i64 %277
%279 = load double, double* %278
%280 = fadd double %279, %273
store double %280, double* %278
%281 = load double, double* %12
%282 = load double*, double** %5
%283 = load i32, i32* %8
%284 = sext i32 %283 to i64
%285 = getelementptr inbounds double, double* %282, i64 %284
store double %281, double* %285
%286 = load double, double* %13
%287 = load double*, double** %5
%288 = load i32, i32* %8
%289 = add nsw i32 %288, 1
%290 = sext i32 %289 to i64
%291 = getelementptr inbounds double, double* %287, i64 %290
store double %286, double* %291
br label %292
292: ; preds = %229
%293 = load i32, i32* %7
%294 = add nsw i32 %293, 2
store i32 %294, i32* %7
br label %225
295: ; preds = %225
br label %296
296: ; preds = %295, %219
br label %297
297: ; preds = %296, %218
ret void
}

LLVM IR (-O2):
define void @cftfsub(i32 %0, double* %1, double* %2) {
%4 = icmp sgt i32 %0, 15
br i1 %4, label %5, label %12
5: ; preds = %3
tail call void @cft1st(i32 %0, double* %1, double* %2)
%6 = icmp ult i32 %0, 128
br i1 %6, label %12, label %7
7: ; preds = %5, %7
%8 = phi i32 [ %10, %7 ], [ 128, %5 ]
%9 = phi i32 [ %8, %7 ], [ 16, %5 ]
tail call void @cftmdl(i32 %0, i32 %9, double* %1, double* %2)
%10 = shl i32 %8, 3
%11 = icmp sgt i32 %10, %0
br i1 %11, label %12, label %7
12: ; preds = %7, %5, %3
%13 = phi i32 [ 2, %3 ], [ 16, %5 ], [ %8, %7 ]
%14 = shl i32 %13, 1
%15 = icmp slt i32 %14, %0
br i1 %15, label %16, label %77
16: ; preds = %12
%17 = icmp sgt i32 %13, 0
br i1 %17, label %18, label %106
18: ; preds = %16
%19 = zext i32 %13 to i64
%20 = shl i32 %13, 1
br label %21
21: ; preds = %18, %21
%22 = phi i64 [ 0, %18 ], [ %75, %21 ]
%23 = trunc i64 %22 to i32
%24 = add nuw nsw i64 %22, %19
%25 = add nuw nsw i64 %24, %19
%26 = add i32 %20, %23
%27 = add nuw nsw i64 %25, %19
%28 = getelementptr inbounds double, double* %1, i64 %22
%29 = getelementptr inbounds double, double* %1, i64 %24
%30 = load double, double* %29
%31 = bitcast double* %28 to <2 x double>*
%32 = load <2 x double>, <2 x double>* %31
%33 = shl i64 %24, 32
%34 = ashr exact i64 %33, 32
%35 = or i64 %34, 1
%36 = getelementptr inbounds double, double* %1, i64 %35
%37 = load double, double* %36
%38 = insertelement <2 x double> poison, double %30, i64 0
%39 = insertelement <2 x double> %38, double %37, i64 1
%40 = fadd <2 x double> %32, %39
%41 = extractelement <2 x double> %32, i64 0
%42 = fsub double %41, %30
%43 = extractelement <2 x double> %32, i64 1
%44 = fsub double %43, %37
%45 = getelementptr inbounds double, double* %1, i64 %25
%46 = load double, double* %45
%47 = getelementptr inbounds double, double* %1, i64 %27
%48 = load double, double* %47
%49 = or i32 %26, 1
%50 = sext i32 %49 to i64
%51 = getelementptr inbounds double, double* %1, i64 %50
%52 = load double, double* %51
%53 = shl i64 %27, 32
%54 = ashr exact i64 %53, 32
%55 = or i64 %54, 1
%56 = getelementptr inbounds double, double* %1, i64 %55
%57 = load double, double* %56
%58 = insertelement <2 x double> poison, double %46, i64 0
%59 = insertelement <2 x double> %58, double %52, i64 1
%60 = insertelement <2 x double> poison, double %48, i64 0
%61 = insertelement <2 x double> %60, double %57, i64 1
%62 = fadd <2 x double> %59, %61
%63 = fsub double %46, %48
%64 = fsub double %52, %57
%65 = fadd <2 x double> %40, %62
%66 = bitcast double* %28 to <2 x double>*
store <2 x double> %65, <2 x double>* %66
%67 = fsub <2 x double> %40, %62
%68 = extractelement <2 x double> %67, i64 0
store double %68, double* %45
%69 = fsub <2 x double> %40, %62
%70 = extractelement <2 x double> %69, i64 1
store double %70, double* %51
%71 = fsub double %42, %64
store double %71, double* %29
%72 = fadd double %44, %63
store double %72, double* %36
%73 = fadd double %42, %64
store double %73, double* %47
%74 = fsub double %44, %63
store double %74, double* %56
%75 = add nuw nsw i64 %22, 2
%76 = icmp ult i64 %75, %19
br i1 %76, label %21, label %106
77: ; preds = %12
%78 = icmp eq i32 %14, %0
%79 = icmp sgt i32 %13, 0
%80 = and i1 %78, %79
br i1 %80, label %81, label %106
81: ; preds = %77
%82 = zext i32 %13 to i64
br label %83
83: ; preds = %81, %83
%84 = phi i64 [ 0, %81 ], [ %104, %83 ]
%85 = add nuw nsw i64 %84, %82
%86 = getelementptr inbounds double, double* %1, i64 %84
%87 = getelementptr inbounds double, double* %1, i64 %85
%88 = load double, double* %87
%89 = bitcast double* %86 to <2 x double>*
%90 = load <2 x double>, <2 x double>* %89
%91 = extractelement <2 x double> %90, i64 0
%92 = fsub double %91, %88
%93 = shl i64 %85, 32
%94 = ashr exact i64 %93, 32
%95 = or i64 %94, 1
%96 = getelementptr inbounds double, double* %1, i64 %95
%97 = load double, double* %96
%98 = extractelement <2 x double> %90, i64 1
%99 = fsub double %98, %97
%100 = insertelement <2 x double> poison, double %88, i64 0
%101 = insertelement <2 x double> %100, double %97, i64 1
%102 = fadd <2 x double> %90, %101
%103 = bitcast double* %86 to <2 x double>*
store <2 x double> %102, <2 x double>* %103
store double %92, double* %87
store double %99, double* %96
%104 = add nuw nsw i64 %84, 2
%105 = icmp ult i64 %104, %82
br i1 %105, label %83, label %106
106: ; preds = %83, %21, %16, %77
ret void
}