void cftfsub(int n, double *a) {
  void cft1st(int n, double *a);
  void cftmdl(int n, int l, double *a);
  int j, j1, j2, j3, l;
  double x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;
  l = 2;
  if (n > 8) {
    cft1st(n, a);
    l = 8;
    while ((l << 2) < n) {
      cftmdl(n, l, a);
      l <<= 2;
    }
  }
  if ((l << 2) == 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 {
    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)
movl   $0x2,-0x24(%rbp)
cmpl   $0x8,-0x4(%rbp)
jle    1184 <cftfsub+0x64>
mov    -0x4(%rbp),%edi
mov    -0x10(%rbp),%rsi
call   1030 <cft1st@plt>
movl   $0x8,-0x24(%rbp)
mov    -0x24(%rbp),%eax
shl    $0x2,%eax
cmp    -0x4(%rbp),%eax
jge    117f <cftfsub+0x5f>
mov    -0x4(%rbp),%edi
mov    -0x24(%rbp),%esi
mov    -0x10(%rbp),%rdx
call   1040 <cftmdl@plt>
mov    -0x24(%rbp),%eax
shl    $0x2,%eax
mov    %eax,-0x24(%rbp)
jmp    1153 <cftfsub+0x33>
jmp    1184 <cftfsub+0x64>
mov    -0x24(%rbp),%eax
shl    $0x2,%eax
cmp    -0x4(%rbp),%eax
jne    13c0 <cftfsub+0x2a0>
movl   $0x0,-0x14(%rbp)
mov    -0x14(%rbp),%eax
cmp    -0x24(%rbp),%eax
jge    13bb <cftfsub+0x29b>
mov    -0x14(%rbp),%eax
add    -0x24(%rbp),%eax
mov    %eax,-0x18(%rbp)
mov    -0x18(%rbp),%eax
add    -0x24(%rbp),%eax
mov    %eax,-0x1c(%rbp)
mov    -0x1c(%rbp),%eax
add    -0x24(%rbp),%eax
mov    %eax,-0x20(%rbp)
mov    -0x10(%rbp),%rax
movslq -0x14(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x18(%rbp),%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x30(%rbp)
mov    -0x10(%rbp),%rax
mov    -0x14(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x18(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x38(%rbp)
mov    -0x10(%rbp),%rax
movslq -0x14(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x18(%rbp),%rcx
subsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x40(%rbp)
mov    -0x10(%rbp),%rax
mov    -0x14(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x18(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
subsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x48(%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,-0x50(%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,-0x58(%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,-0x60(%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,-0x68(%rbp)
movsd  -0x30(%rbp),%xmm0
addsd  -0x50(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x14(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x38(%rbp),%xmm0
addsd  -0x58(%rbp),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x14(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x30(%rbp),%xmm0
subsd  -0x50(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x1c(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x38(%rbp),%xmm0
subsd  -0x58(%rbp),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x1c(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x40(%rbp),%xmm0
subsd  -0x68(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x18(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x48(%rbp),%xmm0
addsd  -0x60(%rbp),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x18(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x40(%rbp),%xmm0
addsd  -0x68(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x20(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x48(%rbp),%xmm0
subsd  -0x60(%rbp),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x20(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x14(%rbp),%eax
add    $0x2,%eax
mov    %eax,-0x14(%rbp)
jmp    119a <cftfsub+0x7a>
jmp    14a8 <cftfsub+0x388>
movl   $0x0,-0x14(%rbp)
mov    -0x14(%rbp),%eax
cmp    -0x24(%rbp),%eax
jge    14a3 <cftfsub+0x383>
mov    -0x14(%rbp),%eax
add    -0x24(%rbp),%eax
mov    %eax,-0x18(%rbp)
mov    -0x10(%rbp),%rax
movslq -0x14(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x18(%rbp),%rcx
subsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x30(%rbp)
mov    -0x10(%rbp),%rax
mov    -0x14(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x18(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
subsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x38(%rbp)
mov    -0x10(%rbp),%rax
movslq -0x18(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x14(%rbp),%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x10(%rbp),%rax
mov    -0x18(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x14(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x30(%rbp),%xmm0
mov    -0x10(%rbp),%rax
movslq -0x18(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x38(%rbp),%xmm0
mov    -0x10(%rbp),%rax
mov    -0x18(%rbp),%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x14(%rbp),%eax
add    $0x2,%eax
mov    %eax,-0x14(%rbp)
jmp    13c7 <cftfsub+0x2a7>
jmp    14a8 <cftfsub+0x388>
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,%r14d
mov    $0x2,%r15d
cmp    $0x9,%edi
jl     117e <cftfsub+0x5e>
mov    %r14d,%edi
mov    %rbx,%rsi
call   1030 <cft1st@plt>
mov    $0x8,%r15d
cmp    $0x21,%r14d
jb     117e <cftfsub+0x5e>
mov    $0x8,%esi
mov    $0x20,%eax
nopl   0x0(%rax)
mov    %eax,%r15d
mov    %r14d,%edi
mov    %rbx,%rdx
call   1040 <cftmdl@plt>
lea    0x0(,%r15,4),%eax
mov    %r15d,%esi
cmp    %r14d,%eax
jl     1160 <cftfsub+0x40>
lea    0x0(,%r15,4),%eax
cmp    %r14d,%eax
jne    12a2 <cftfsub+0x182>
test   %r15d,%r15d
jle    131d <cftfsub+0x1fd>
movabs $0x200000000,%r8
mov    %r15d,%r9d
add    %r15d,%r15d
or     $0x1,%r15
mov    %r9,%rax
shl    $0x20,%rax
lea    (%rbx,%r9,8),%r10
lea    (%rax,%rax,2),%rcx
lea    (%r9,%r9,2),%rdx
lea    (%rbx,%rdx,8),%r11
mov    %r9,%r14
shl    $0x4,%r14
add    %rbx,%r14
xor    %esi,%esi
nop
movsd  (%r10,%rsi,8),%xmm2
movupd (%rbx,%rsi,8),%xmm0
mov    %rax,%rdx
sar    $0x1d,%rdx
or     $0x8,%rdx
movsd  (%rbx,%rdx,1),%xmm3
movapd %xmm0,%xmm1
subsd  %xmm2,%xmm1
unpcklpd %xmm3,%xmm2
addpd  %xmm0,%xmm2
unpckhpd %xmm0,%xmm0
subsd  %xmm3,%xmm0
movsd  (%r14,%rsi,8),%xmm3
movsd  (%r11,%rsi,8),%xmm4
lea    (%r15,%rsi,1),%edi
movslq %edi,%rbp
movsd  (%rbx,%rbp,8),%xmm5
mov    %rcx,%rdi
sar    $0x1d,%rdi
or     $0x8,%rdi
movsd  (%rbx,%rdi,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,%rsi,8)
subpd  %xmm4,%xmm2
movlpd %xmm2,(%r14,%rsi,8)
movhpd %xmm2,(%rbx,%rbp,8)
movapd %xmm1,%xmm2
subsd  %xmm5,%xmm2
movsd  %xmm2,(%r10,%rsi,8)
movapd %xmm0,%xmm2
addsd  %xmm3,%xmm2
movsd  %xmm2,(%rbx,%rdx,1)
addsd  %xmm1,%xmm5
movsd  %xmm5,(%r11,%rsi,8)
subsd  %xmm3,%xmm0
movsd  %xmm0,(%rbx,%rdi,1)
add    $0x2,%rsi
add    %r8,%rax
add    %r8,%rcx
cmp    %r9,%rsi
jb     11d0 <cftfsub+0xb0>
jmp    131d <cftfsub+0x1fd>
test   %r15d,%r15d
jle    131d <cftfsub+0x1fd>
movabs $0x200000000,%rax
mov    %r15d,%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) {
%3 = alloca i32
%4 = alloca double*
%5 = alloca i32
%6 = alloca i32
%7 = alloca i32
%8 = alloca i32
%9 = alloca i32
%10 = alloca double
%11 = alloca double
%12 = alloca double
%13 = alloca double
%14 = alloca double
%15 = alloca double
%16 = alloca double
%17 = alloca double
store i32 %0, i32* %3
store double* %1, double** %4
store i32 2, i32* %9
%18 = load i32, i32* %3
%19 = icmp sgt i32 %18, 8
br i1 %19, label %20, label %35
20: ; preds = %2
%21 = load i32, i32* %3
%22 = load double*, double** %4
store i32 8, i32* %9
br label %23
23: ; preds = %28, %20
%24 = load i32, i32* %9
%25 = shl i32 %24, 2
%26 = load i32, i32* %3
%27 = icmp slt i32 %25, %26
br i1 %27, label %28, label %34
28: ; preds = %23
%29 = load i32, i32* %3
%30 = load i32, i32* %9
%31 = load double*, double** %4
%32 = load i32, i32* %9
%33 = shl i32 %32, 2
store i32 %33, i32* %9
br label %23
34: ; preds = %23
br label %35
35: ; preds = %34, %2
%36 = load i32, i32* %9
%37 = shl i32 %36, 2
%38 = load i32, i32* %3
%39 = icmp eq i32 %37, %38
br i1 %39, label %40, label %215
40: ; preds = %35
store i32 0, i32* %5
br label %41
41: ; preds = %211, %40
%42 = load i32, i32* %5
%43 = load i32, i32* %9
%44 = icmp slt i32 %42, %43
br i1 %44, label %45, label %214
45: ; preds = %41
%46 = load i32, i32* %5
%47 = load i32, i32* %9
%48 = add nsw i32 %46, %47
store i32 %48, i32* %6
%49 = load i32, i32* %6
%50 = load i32, i32* %9
%51 = add nsw i32 %49, %50
store i32 %51, i32* %7
%52 = load i32, i32* %7
%53 = load i32, i32* %9
%54 = add nsw i32 %52, %53
store i32 %54, i32* %8
%55 = load double*, double** %4
%56 = load i32, i32* %5
%57 = sext i32 %56 to i64
%58 = getelementptr inbounds double, double* %55, i64 %57
%59 = load double, double* %58
%60 = load double*, double** %4
%61 = load i32, i32* %6
%62 = sext i32 %61 to i64
%63 = getelementptr inbounds double, double* %60, i64 %62
%64 = load double, double* %63
%65 = fadd double %59, %64
store double %65, double* %10
%66 = load double*, double** %4
%67 = load i32, i32* %5
%68 = add nsw i32 %67, 1
%69 = sext i32 %68 to i64
%70 = getelementptr inbounds double, double* %66, i64 %69
%71 = load double, double* %70
%72 = load double*, double** %4
%73 = load i32, i32* %6
%74 = add nsw i32 %73, 1
%75 = sext i32 %74 to i64
%76 = getelementptr inbounds double, double* %72, i64 %75
%77 = load double, double* %76
%78 = fadd double %71, %77
store double %78, double* %11
%79 = load double*, double** %4
%80 = load i32, i32* %5
%81 = sext i32 %80 to i64
%82 = getelementptr inbounds double, double* %79, i64 %81
%83 = load double, double* %82
%84 = load double*, double** %4
%85 = load i32, i32* %6
%86 = sext i32 %85 to i64
%87 = getelementptr inbounds double, double* %84, i64 %86
%88 = load double, double* %87
%89 = fsub double %83, %88
store double %89, double* %12
%90 = load double*, double** %4
%91 = load i32, i32* %5
%92 = add nsw i32 %91, 1
%93 = sext i32 %92 to i64
%94 = getelementptr inbounds double, double* %90, i64 %93
%95 = load double, double* %94
%96 = load double*, double** %4
%97 = load i32, i32* %6
%98 = add nsw i32 %97, 1
%99 = sext i32 %98 to i64
%100 = getelementptr inbounds double, double* %96, i64 %99
%101 = load double, double* %100
%102 = fsub double %95, %101
store double %102, double* %13
%103 = load double*, double** %4
%104 = load i32, i32* %7
%105 = sext i32 %104 to i64
%106 = getelementptr inbounds double, double* %103, i64 %105
%107 = load double, double* %106
%108 = load double*, double** %4
%109 = load i32, i32* %8
%110 = sext i32 %109 to i64
%111 = getelementptr inbounds double, double* %108, i64 %110
%112 = load double, double* %111
%113 = fadd double %107, %112
store double %113, double* %14
%114 = load double*, double** %4
%115 = load i32, i32* %7
%116 = add nsw i32 %115, 1
%117 = sext i32 %116 to i64
%118 = getelementptr inbounds double, double* %114, i64 %117
%119 = load double, double* %118
%120 = load double*, double** %4
%121 = load i32, i32* %8
%122 = add nsw i32 %121, 1
%123 = sext i32 %122 to i64
%124 = getelementptr inbounds double, double* %120, i64 %123
%125 = load double, double* %124
%126 = fadd double %119, %125
store double %126, double* %15
%127 = load double*, double** %4
%128 = load i32, i32* %7
%129 = sext i32 %128 to i64
%130 = getelementptr inbounds double, double* %127, i64 %129
%131 = load double, double* %130
%132 = load double*, double** %4
%133 = load i32, i32* %8
%134 = sext i32 %133 to i64
%135 = getelementptr inbounds double, double* %132, i64 %134
%136 = load double, double* %135
%137 = fsub double %131, %136
store double %137, double* %16
%138 = load double*, double** %4
%139 = load i32, i32* %7
%140 = add nsw i32 %139, 1
%141 = sext i32 %140 to i64
%142 = getelementptr inbounds double, double* %138, i64 %141
%143 = load double, double* %142
%144 = load double*, double** %4
%145 = load i32, i32* %8
%146 = add nsw i32 %145, 1
%147 = sext i32 %146 to i64
%148 = getelementptr inbounds double, double* %144, i64 %147
%149 = load double, double* %148
%150 = fsub double %143, %149
store double %150, double* %17
%151 = load double, double* %10
%152 = load double, double* %14
%153 = fadd double %151, %152
%154 = load double*, double** %4
%155 = load i32, i32* %5
%156 = sext i32 %155 to i64
%157 = getelementptr inbounds double, double* %154, i64 %156
store double %153, double* %157
%158 = load double, double* %11
%159 = load double, double* %15
%160 = fadd double %158, %159
%161 = load double*, double** %4
%162 = load i32, i32* %5
%163 = add nsw i32 %162, 1
%164 = sext i32 %163 to i64
%165 = getelementptr inbounds double, double* %161, i64 %164
store double %160, double* %165
%166 = load double, double* %10
%167 = load double, double* %14
%168 = fsub double %166, %167
%169 = load double*, double** %4
%170 = load i32, i32* %7
%171 = sext i32 %170 to i64
%172 = getelementptr inbounds double, double* %169, i64 %171
store double %168, double* %172
%173 = load double, double* %11
%174 = load double, double* %15
%175 = fsub double %173, %174
%176 = load double*, double** %4
%177 = load i32, i32* %7
%178 = add nsw i32 %177, 1
%179 = sext i32 %178 to i64
%180 = getelementptr inbounds double, double* %176, i64 %179
store double %175, double* %180
%181 = load double, double* %12
%182 = load double, double* %17
%183 = fsub double %181, %182
%184 = load double*, double** %4
%185 = load i32, i32* %6
%186 = sext i32 %185 to i64
%187 = getelementptr inbounds double, double* %184, i64 %186
store double %183, double* %187
%188 = load double, double* %13
%189 = load double, double* %16
%190 = fadd double %188, %189
%191 = load double*, double** %4
%192 = load i32, i32* %6
%193 = add nsw i32 %192, 1
%194 = sext i32 %193 to i64
%195 = getelementptr inbounds double, double* %191, i64 %194
store double %190, double* %195
%196 = load double, double* %12
%197 = load double, double* %17
%198 = fadd double %196, %197
%199 = load double*, double** %4
%200 = load i32, i32* %8
%201 = sext i32 %200 to i64
%202 = getelementptr inbounds double, double* %199, i64 %201
store double %198, double* %202
%203 = load double, double* %13
%204 = load double, double* %16
%205 = fsub double %203, %204
%206 = load double*, double** %4
%207 = load i32, i32* %8
%208 = add nsw i32 %207, 1
%209 = sext i32 %208 to i64
%210 = getelementptr inbounds double, double* %206, i64 %209
store double %205, double* %210
br label %211
211: ; preds = %45
%212 = load i32, i32* %5
%213 = add nsw i32 %212, 2
store i32 %213, i32* %5
br label %41
214: ; preds = %41
br label %287
215: ; preds = %35
store i32 0, i32* %5
br label %216
216: ; preds = %283, %215
%217 = load i32, i32* %5
%218 = load i32, i32* %9
%219 = icmp slt i32 %217, %218
br i1 %219, label %220, label %286
220: ; preds = %216
%221 = load i32, i32* %5
%222 = load i32, i32* %9
%223 = add nsw i32 %221, %222
store i32 %223, i32* %6
%224 = load double*, double** %4
%225 = load i32, i32* %5
%226 = sext i32 %225 to i64
%227 = getelementptr inbounds double, double* %224, i64 %226
%228 = load double, double* %227
%229 = load double*, double** %4
%230 = load i32, i32* %6
%231 = sext i32 %230 to i64
%232 = getelementptr inbounds double, double* %229, i64 %231
%233 = load double, double* %232
%234 = fsub double %228, %233
store double %234, double* %10
%235 = load double*, double** %4
%236 = load i32, i32* %5
%237 = add nsw i32 %236, 1
%238 = sext i32 %237 to i64
%239 = getelementptr inbounds double, double* %235, i64 %238
%240 = load double, double* %239
%241 = load double*, double** %4
%242 = load i32, i32* %6
%243 = add nsw i32 %242, 1
%244 = sext i32 %243 to i64
%245 = getelementptr inbounds double, double* %241, i64 %244
%246 = load double, double* %245
%247 = fsub double %240, %246
store double %247, double* %11
%248 = load double*, double** %4
%249 = load i32, i32* %6
%250 = sext i32 %249 to i64
%251 = getelementptr inbounds double, double* %248, i64 %250
%252 = load double, double* %251
%253 = load double*, double** %4
%254 = load i32, i32* %5
%255 = sext i32 %254 to i64
%256 = getelementptr inbounds double, double* %253, i64 %255
%257 = load double, double* %256
%258 = fadd double %257, %252
store double %258, double* %256
%259 = load double*, double** %4
%260 = load i32, i32* %6
%261 = add nsw i32 %260, 1
%262 = sext i32 %261 to i64
%263 = getelementptr inbounds double, double* %259, i64 %262
%264 = load double, double* %263
%265 = load double*, double** %4
%266 = load i32, i32* %5
%267 = add nsw i32 %266, 1
%268 = sext i32 %267 to i64
%269 = getelementptr inbounds double, double* %265, i64 %268
%270 = load double, double* %269
%271 = fadd double %270, %264
store double %271, double* %269
%272 = load double, double* %10
%273 = load double*, double** %4
%274 = load i32, i32* %6
%275 = sext i32 %274 to i64
%276 = getelementptr inbounds double, double* %273, i64 %275
store double %272, double* %276
%277 = load double, double* %11
%278 = load double*, double** %4
%279 = load i32, i32* %6
%280 = add nsw i32 %279, 1
%281 = sext i32 %280 to i64
%282 = getelementptr inbounds double, double* %278, i64 %281
store double %277, double* %282
br label %283
283: ; preds = %220
%284 = load i32, i32* %5
%285 = add nsw i32 %284, 2
store i32 %285, i32* %5
br label %216
286: ; preds = %216
br label %287
287: ; preds = %286, %214
ret void
}

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