#define NULL ((void *)0)
typedef unsigned long size_t; // Customize by platform.
typedef long intptr_t;
typedef unsigned long uintptr_t;
typedef long scalar_t__; // Either arithmetic or pointer type.
/* By default, we understand bool (as a convenience). */
typedef int bool;
#define false 0
#define true 1

/* Forward declarations */

/* Type definitions */

/* Variables and functions */
double M_PI;
int /*<<< orphan*/ four1(double *, unsigned long, int);
double sin(double);
void realft(double *data, unsigned long n, int isign) {
  unsigned long i, i1, i2, i3, i4, np3;
  double c1 = 0.5, c2, h1r, h1i, h2r, h2i;
  double wr, wi, wpr, wpi, wtemp, theta;
  theta = M_PI / (double)(n >> 1);
  if (isign == 1) {
    c2 = -0.5;
    four1(data, n >> 1, 1);
  } else {
    c2 = 0.5;
    theta = -theta;
  }
  wtemp = sin(0.5 * theta);
  wpr = -2.0 * wtemp * wtemp;
  wpi = sin(theta);
  wr = 1.0 + wpr;
  wi = wpi;
  np3 = n + 3;
  for (i = 2; i <= (n >> 2); i++) {
    i4 = 1 + (i3 = np3 - (i2 = 1 + (i1 = i + i - 1)));
    h1r = c1 * (data[i1] + data[i3]);
    h1i = c1 * (data[i2] - data[i4]);
    h2r = -c2 * (data[i2] + data[i4]);
    h2i = c2 * (data[i1] - data[i3]);
    data[i1] = h1r + wr * h2r - wi * h2i;
    data[i2] = h1i + wr * h2i + wi * h2r;
    data[i3] = h1r - wr * h2r + wi * h2i;
    data[i4] = -h1i + wr * h2i + wi * h2r;
    wr = (wtemp = wr) * wpr - wi * wpi + wr;
    wi = wi * wpr + wtemp * wpi + wi;
  }
  if (isign == 1) {
    data[1] = (h1r = data[1]) + data[2];
    data[2] = h1r - data[2];
  } else {
    data[1] = c1 * ((h1r = data[1]) + data[2]);
    data[2] = c1 * (h1r - data[2]);
    four1(data, n >> 1, -1);
  }
}


x86 assembly (clang, -O0):
<realft>:
push   %rbp
mov    %rsp,%rbp
sub    $0xb0,%rsp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    %edx,-0x14(%rbp)
movabs $0x3fe0000000000000,%rax
mov    %rax,-0x50(%rbp)
mov    0x2e9d(%rip),%rax
movsd  (%rax),%xmm0
mov    -0x10(%rbp),%rax
shr    %rax
cvtsi2sd %rax,%xmm1
divsd  %xmm1,%xmm0
movsd  %xmm0,-0xa8(%rbp)
ff
cmpl   $0x1,-0x14(%rbp)
jne    1199 <realft+0x79>
movsd  0xe8f(%rip),%xmm0
movsd  %xmm0,-0x58(%rbp)
mov    -0x8(%rbp),%rdi
mov    -0x10(%rbp),%rsi
shr    $0x1,%rsi
mov    $0x1,%edx
call   1030 <four1@plt>
jmp    11cd <realft+0xad>
movsd  0xe5f(%rip),%xmm0
movsd  %xmm0,-0x58(%rbp)
movsd  -0xa8(%rbp),%xmm0
ff
movq   %xmm0,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm0
movsd  %xmm0,-0xa8(%rbp)
ff
movsd  0xe2b(%rip),%xmm0
mulsd  -0xa8(%rbp),%xmm0
ff
call   1040 <sin@plt>
movsd  %xmm0,-0xa0(%rbp)
ff
movsd  0xe26(%rip),%xmm0
mulsd  -0xa0(%rbp),%xmm0
ff
mulsd  -0xa0(%rbp),%xmm0
ff
movsd  %xmm0,-0x90(%rbp)
ff
movsd  -0xa8(%rbp),%xmm0
ff
call   1040 <sin@plt>
movsd  %xmm0,-0x98(%rbp)
ff
movsd  0xde9(%rip),%xmm0
addsd  -0x90(%rbp),%xmm0
ff
movsd  %xmm0,-0x80(%rbp)
movsd  -0x98(%rbp),%xmm0
ff
movsd  %xmm0,-0x88(%rbp)
ff
mov    -0x10(%rbp),%rax
add    $0x3,%rax
mov    %rax,-0x48(%rbp)
movq   $0x2,-0x20(%rbp)
mov    -0x20(%rbp),%rax
mov    -0x10(%rbp),%rcx
shr    $0x2,%rcx
cmp    %rcx,%rax
ja     150f <realft+0x3ef>
mov    -0x48(%rbp),%rax
mov    -0x20(%rbp),%rcx
add    -0x20(%rbp),%rcx
sub    $0x1,%rcx
mov    %rcx,-0x28(%rbp)
add    $0x1,%rcx
mov    %rcx,-0x30(%rbp)
sub    %rcx,%rax
mov    %rax,-0x38(%rbp)
add    $0x1,%rax
mov    %rax,-0x40(%rbp)
movsd  -0x50(%rbp),%xmm0
mov    -0x8(%rbp),%rax
mov    -0x28(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm1
mov    -0x8(%rbp),%rax
mov    -0x38(%rbp),%rcx
addsd  (%rax,%rcx,8),%xmm1
mulsd  %xmm1,%xmm0
movsd  %xmm0,-0x60(%rbp)
movsd  -0x50(%rbp),%xmm0
mov    -0x8(%rbp),%rax
mov    -0x30(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm1
mov    -0x8(%rbp),%rax
mov    -0x40(%rbp),%rcx
subsd  (%rax,%rcx,8),%xmm1
mulsd  %xmm1,%xmm0
movsd  %xmm0,-0x68(%rbp)
movsd  -0x58(%rbp),%xmm0
movq   %xmm0,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm0
mov    -0x8(%rbp),%rax
mov    -0x30(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm1
mov    -0x8(%rbp),%rax
mov    -0x40(%rbp),%rcx
addsd  (%rax,%rcx,8),%xmm1
mulsd  %xmm1,%xmm0
movsd  %xmm0,-0x70(%rbp)
movsd  -0x58(%rbp),%xmm0
mov    -0x8(%rbp),%rax
mov    -0x28(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm1
mov    -0x8(%rbp),%rax
mov    -0x38(%rbp),%rcx
subsd  (%rax,%rcx,8),%xmm1
mulsd  %xmm1,%xmm0
movsd  %xmm0,-0x78(%rbp)
movsd  -0x60(%rbp),%xmm0
movsd  -0x80(%rbp),%xmm1
movsd  -0x70(%rbp),%xmm2
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
movsd  -0x88(%rbp),%xmm0
ff
movsd  -0x78(%rbp),%xmm2
movq   %xmm0,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm0
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
mov    -0x28(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x68(%rbp),%xmm0
movsd  -0x80(%rbp),%xmm1
movsd  -0x78(%rbp),%xmm2
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
movsd  -0x88(%rbp),%xmm0
ff
movsd  -0x70(%rbp),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
mov    -0x30(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x60(%rbp),%xmm0
movsd  -0x80(%rbp),%xmm1
movsd  -0x70(%rbp),%xmm2
movq   %xmm1,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm1
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
movsd  -0x88(%rbp),%xmm0
ff
movsd  -0x78(%rbp),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
mov    -0x38(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x68(%rbp),%xmm0
movq   %xmm0,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm0
movsd  -0x80(%rbp),%xmm1
movsd  -0x78(%rbp),%xmm2
mulsd  %xmm2,%xmm1
addsd  %xmm0,%xmm1
movsd  -0x88(%rbp),%xmm0
ff
movsd  -0x70(%rbp),%xmm2
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
mov    -0x40(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x80(%rbp),%xmm0
movsd  %xmm0,-0xa0(%rbp)
ff
movsd  -0x90(%rbp),%xmm2
ff
movsd  -0x88(%rbp),%xmm1
ff
mulsd  -0x98(%rbp),%xmm1
ff
movq   %xmm1,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
addsd  -0x80(%rbp),%xmm0
movsd  %xmm0,-0x80(%rbp)
movsd  -0x88(%rbp),%xmm0
ff
movsd  -0x90(%rbp),%xmm2
ff
movsd  -0xa0(%rbp),%xmm1
ff
mulsd  -0x98(%rbp),%xmm1
ff
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
addsd  -0x88(%rbp),%xmm0
ff
movsd  %xmm0,-0x88(%rbp)
ff
mov    -0x20(%rbp),%rax
add    $0x1,%rax
mov    %rax,-0x20(%rbp)
jmp    1258 <realft+0x138>
cmpl   $0x1,-0x14(%rbp)
jne    1555 <realft+0x435>
mov    -0x8(%rbp),%rax
movsd  0x8(%rax),%xmm0
movsd  %xmm0,-0x60(%rbp)
mov    -0x8(%rbp),%rax
addsd  0x10(%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,0x8(%rax)
movsd  -0x60(%rbp),%xmm0
mov    -0x8(%rbp),%rax
subsd  0x10(%rax),%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,0x10(%rax)
jmp    15b4 <realft+0x494>
movsd  -0x50(%rbp),%xmm0
mov    -0x8(%rbp),%rax
movsd  0x8(%rax),%xmm1
movsd  %xmm1,-0x60(%rbp)
mov    -0x8(%rbp),%rax
addsd  0x10(%rax),%xmm1
mulsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,0x8(%rax)
movsd  -0x50(%rbp),%xmm0
movsd  -0x60(%rbp),%xmm1
mov    -0x8(%rbp),%rax
subsd  0x10(%rax),%xmm1
mulsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
movsd  %xmm0,0x10(%rax)
mov    -0x8(%rbp),%rdi
mov    -0x10(%rbp),%rsi
shr    $0x1,%rsi
mov    $0xffffffff,%edx
call   1030 <four1@plt>
add    $0xb0,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<realft>:
push   %rbp
push   %r15
push   %r14
push   %rbx
sub    $0x38,%rsp
mov    %edx,%r15d
mov    %rsi,%rbp
mov    %rdi,%rbx
mov    0x2eae(%rip),%rax
movsd  (%rax),%xmm1
mov    %rsi,%r14
shr    %r14
cvtsi2sd %r14,%xmm0
divsd  %xmm0,%xmm1
cmp    $0x1,%edx
jne    1176 <realft+0x56>
mov    %rbx,%rdi
mov    %r14,%rsi
mov    $0x1,%edx
movapd %xmm1,(%rsp)
call   1030 <four1@plt>
movapd (%rsp),%xmm1
movsd  0xeb4(%rip),%xmm0
jmp    1186 <realft+0x66>
xorpd  0xe82(%rip),%xmm1
movsd  0xe9a(%rip),%xmm0
movaps %xmm0,0x20(%rsp)
movapd %xmm1,(%rsp)
movsd  0xe88(%rip),%xmm0
mulsd  %xmm1,%xmm0
call   1040 <sin@plt>
movsd  %xmm0,0x18(%rsp)
movapd (%rsp),%xmm0
call   1040 <sin@plt>
cmp    $0x8,%rbp
movapd 0x20(%rsp),%xmm12
jb     130e <realft+0x1ee>
movsd  0xe65(%rip),%xmm9
movsd  0x18(%rsp),%xmm1
mulsd  %xmm1,%xmm9
mulsd  %xmm1,%xmm9
lea    (%rbx,%rbp,8),%rax
add    $0xfffffffffffffff8,%rax
shr    $0x2,%rbp
movsd  0xe49(%rip),%xmm2
addsd  %xmm9,%xmm2
movapd 0xe04(%rip),%xmm1
xorpd  %xmm12,%xmm1
movapd %xmm0,%xmm11
unpcklpd %xmm2,%xmm11
unpcklpd %xmm1,%xmm12
unpcklpd %xmm9,%xmm9
unpcklpd %xmm0,%xmm0
add    $0xffffffffffffffff,%rbp
lea    0x18(%rbx),%rcx
movapd 0xde6(%rip),%xmm8
movapd 0xdcd(%rip),%xmm10
cs nopw 0x0(%rax,%rax,1)
nopl   (%rax)
movupd (%rcx),%xmm6
movupd (%rax),%xmm5
movapd %xmm6,%xmm7
addpd  %xmm5,%xmm7
subpd  %xmm5,%xmm6
movapd %xmm6,%xmm5
movsd  %xmm7,%xmm5
mulpd  %xmm8,%xmm5
shufpd $0x2,%xmm7,%xmm6
mulpd  %xmm12,%xmm6
movapd %xmm11,%xmm7
xorpd  %xmm10,%xmm7
movapd %xmm11,%xmm2
shufpd $0x1,%xmm7,%xmm2
unpcklpd %xmm11,%xmm7
mulpd  %xmm6,%xmm7
movapd %xmm11,%xmm3
unpcklpd %xmm11,%xmm3
mulpd  %xmm6,%xmm3
shufpd $0x1,%xmm6,%xmm6
movapd %xmm11,%xmm4
unpckhpd %xmm11,%xmm4
movapd %xmm4,%xmm1
mulpd  %xmm6,%xmm1
addpd  %xmm5,%xmm1
addpd  %xmm1,%xmm7
movupd %xmm7,(%rcx)
xorpd  %xmm10,%xmm4
movapd %xmm5,%xmm1
unpckhpd %xmm5,%xmm1
xorpd  %xmm10,%xmm1
shufpd $0x2,%xmm11,%xmm4
unpcklpd %xmm1,%xmm5
mulpd  %xmm6,%xmm4
addpd  %xmm5,%xmm4
addpd  %xmm4,%xmm3
movupd %xmm3,(%rax)
mulpd  %xmm0,%xmm2
movapd %xmm11,%xmm1
mulpd  %xmm9,%xmm1
addpd  %xmm2,%xmm1
addpd  %xmm1,%xmm11
add    $0xfffffffffffffff0,%rax
add    $0x10,%rcx
add    $0xffffffffffffffff,%rbp
jne    1240 <realft+0x120>
movsd  0x8(%rbx),%xmm0
movsd  0x10(%rbx),%xmm2
movapd %xmm0,%xmm1
addsd  %xmm2,%xmm1
cmp    $0x1,%r15d
jne    133f <realft+0x21f>
movsd  %xmm1,0x8(%rbx)
subsd  %xmm2,%xmm0
movsd  %xmm0,0x10(%rbx)
add    $0x38,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
ret
subsd  %xmm2,%xmm0
unpcklpd %xmm0,%xmm1
mulpd  0xcc1(%rip),%xmm1
movupd %xmm1,0x8(%rbx)
mov    %rbx,%rdi
mov    %r14,%rsi
mov    $0xffffffff,%edx
add    $0x38,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
jmp    1030 <four1@plt>

LLVM IR (-O0):
@M_PI = global double 0.000000e+00
define void @realft(double* %0, i64 %1, i32 %2) {
%4 = alloca double*
%5 = alloca i64
%6 = alloca i32
%7 = alloca i64
%8 = alloca i64
%9 = alloca i64
%10 = alloca i64
%11 = alloca i64
%12 = alloca i64
%13 = alloca double
%14 = alloca double
%15 = alloca double
%16 = alloca double
%17 = alloca double
%18 = alloca double
%19 = alloca double
%20 = alloca double
%21 = alloca double
%22 = alloca double
%23 = alloca double
%24 = alloca double
store double* %0, double** %4
store i64 %1, i64* %5
store i32 %2, i32* %6
store double 5.000000e-01, double* %13
%25 = load double, double* @M_PI
%26 = load i64, i64* %5
%27 = lshr i64 %26, 1
%28 = uitofp i64 %27 to double
%29 = fdiv double %25, %28
store double %29, double* %24
%30 = load i32, i32* %6
%31 = icmp eq i32 %30, 1
br i1 %31, label %32, label %37
32: ; preds = %3
store double -5.000000e-01, double* %14
%33 = load double*, double** %4
%34 = load i64, i64* %5
%35 = lshr i64 %34, 1
%36 = call i32 @four1(double* %33, i64 %35, i32 1)
br label %40
37: ; preds = %3
store double 5.000000e-01, double* %14
%38 = load double, double* %24
%39 = fneg double %38
store double %39, double* %24
br label %40
40: ; preds = %37, %32
%41 = load double, double* %24
%42 = fmul double 5.000000e-01, %41
%43 = call double @sin(double %42)
store double %43, double* %23
%44 = load double, double* %23
%45 = fmul double -2.000000e+00, %44
%46 = load double, double* %23
%47 = fmul double %45, %46
store double %47, double* %21
%48 = load double, double* %24
%49 = call double @sin(double %48)
store double %49, double* %22
%50 = load double, double* %21
%51 = fadd double 1.000000e+00, %50
store double %51, double* %19
%52 = load double, double* %22
store double %52, double* %20
%53 = load i64, i64* %5
%54 = add i64 %53, 3
store i64 %54, i64* %12
store i64 2, i64* %7
br label %55
55: ; preds = %174, %40
%56 = load i64, i64* %7
%57 = load i64, i64* %5
%58 = lshr i64 %57, 2
%59 = icmp ule i64 %56, %58
br i1 %59, label %60, label %177
60: ; preds = %55
%61 = load i64, i64* %12
%62 = load i64, i64* %7
%63 = load i64, i64* %7
%64 = add i64 %62, %63
%65 = sub i64 %64, 1
store i64 %65, i64* %8
%66 = add i64 1, %65
store i64 %66, i64* %9
%67 = sub i64 %61, %66
store i64 %67, i64* %10
%68 = add i64 1, %67
store i64 %68, i64* %11
%69 = load double, double* %13
%70 = load double*, double** %4
%71 = load i64, i64* %8
%72 = getelementptr inbounds double, double* %70, i64 %71
%73 = load double, double* %72
%74 = load double*, double** %4
%75 = load i64, i64* %10
%76 = getelementptr inbounds double, double* %74, i64 %75
%77 = load double, double* %76
%78 = fadd double %73, %77
%79 = fmul double %69, %78
store double %79, double* %15
%80 = load double, double* %13
%81 = load double*, double** %4
%82 = load i64, i64* %9
%83 = getelementptr inbounds double, double* %81, i64 %82
%84 = load double, double* %83
%85 = load double*, double** %4
%86 = load i64, i64* %11
%87 = getelementptr inbounds double, double* %85, i64 %86
%88 = load double, double* %87
%89 = fsub double %84, %88
%90 = fmul double %80, %89
store double %90, double* %16
%91 = load double, double* %14
%92 = fneg double %91
%93 = load double*, double** %4
%94 = load i64, i64* %9
%95 = getelementptr inbounds double, double* %93, i64 %94
%96 = load double, double* %95
%97 = load double*, double** %4
%98 = load i64, i64* %11
%99 = getelementptr inbounds double, double* %97, i64 %98
%100 = load double, double* %99
%101 = fadd double %96, %100
%102 = fmul double %92, %101
store double %102, double* %17
%103 = load double, double* %14
%104 = load double*, double** %4
%105 = load i64, i64* %8
%106 = getelementptr inbounds double, double* %104, i64 %105
%107 = load double, double* %106
%108 = load double*, double** %4
%109 = load i64, i64* %10
%110 = getelementptr inbounds double, double* %108, i64 %109
%111 = load double, double* %110
%112 = fsub double %107, %111
%113 = fmul double %103, %112
store double %113, double* %18
%114 = load double, double* %15
%115 = load double, double* %19
%116 = load double, double* %17
%117 = call double @llvm.fmuladd.f64(double %115, double %116, double %114)
%118 = load double, double* %20
%119 = load double, double* %18
%120 = fneg double %118
%121 = call double @llvm.fmuladd.f64(double %120, double %119, double %117)
%122 = load double*, double** %4
%123 = load i64, i64* %8
%124 = getelementptr inbounds double, double* %122, i64 %123
store double %121, double* %124
%125 = load double, double* %16
%126 = load double, double* %19
%127 = load double, double* %18
%128 = call double @llvm.fmuladd.f64(double %126, double %127, double %125)
%129 = load double, double* %20
%130 = load double, double* %17
%131 = call double @llvm.fmuladd.f64(double %129, double %130, double %128)
%132 = load double*, double** %4
%133 = load i64, i64* %9
%134 = getelementptr inbounds double, double* %132, i64 %133
store double %131, double* %134
%135 = load double, double* %15
%136 = load double, double* %19
%137 = load double, double* %17
%138 = fneg double %136
%139 = call double @llvm.fmuladd.f64(double %138, double %137, double %135)
%140 = load double, double* %20
%141 = load double, double* %18
%142 = call double @llvm.fmuladd.f64(double %140, double %141, double %139)
%143 = load double*, double** %4
%144 = load i64, i64* %10
%145 = getelementptr inbounds double, double* %143, i64 %144
store double %142, double* %145
%146 = load double, double* %16
%147 = fneg double %146
%148 = load double, double* %19
%149 = load double, double* %18
%150 = call double @llvm.fmuladd.f64(double %148, double %149, double %147)
%151 = load double, double* %20
%152 = load double, double* %17
%153 = call double @llvm.fmuladd.f64(double %151, double %152, double %150)
%154 = load double*, double** %4
%155 = load i64, i64* %11
%156 = getelementptr inbounds double, double* %154, i64 %155
store double %153, double* %156
%157 = load double, double* %19
store double %157, double* %23
%158 = load double, double* %21
%159 = load double, double* %20
%160 = load double, double* %22
%161 = fmul double %159, %160
%162 = fneg double %161
%163 = call double @llvm.fmuladd.f64(double %157, double %158, double %162)
%164 = load double, double* %19
%165 = fadd double %163, %164
store double %165, double* %19
%166 = load double, double* %20
%167 = load double, double* %21
%168 = load double, double* %23
%169 = load double, double* %22
%170 = fmul double %168, %169
%171 = call double @llvm.fmuladd.f64(double %166, double %167, double %170)
%172 = load double, double* %20
%173 = fadd double %171, %172
store double %173, double* %20
br label %174
174: ; preds = %60
%175 = load i64, i64* %7
%176 = add i64 %175, 1
store i64 %176, i64* %7
br label %55
177: ; preds = %55
%178 = load i32, i32* %6
%179 = icmp eq i32 %178, 1
br i1 %179, label %180, label %197
180: ; preds = %177
%181 = load double*, double** %4
%182 = getelementptr inbounds double, double* %181, i64 1
%183 = load double, double* %182
store double %183, double* %15
%184 = load double*, double** %4
%185 = getelementptr inbounds double, double* %184, i64 2
%186 = load double, double* %185
%187 = fadd double %183, %186
%188 = load double*, double** %4
%189 = getelementptr inbounds double, double* %188, i64 1
store double %187, double* %189
%190 = load double, double* %15
%191 = load double*, double** %4
%192 = getelementptr inbounds double, double* %191, i64 2
%193 = load double, double* %192
%194 = fsub double %190, %193
%195 = load double*, double** %4
%196 = getelementptr inbounds double, double* %195, i64 2
store double %194, double* %196
br label %222
197: ; preds = %177
%198 = load double, double* %13
%199 = load double*, double** %4
%200 = getelementptr inbounds double, double* %199, i64 1
%201 = load double, double* %200
store double %201, double* %15
%202 = load double*, double** %4
%203 = getelementptr inbounds double, double* %202, i64 2
%204 = load double, double* %203
%205 = fadd double %201, %204
%206 = fmul double %198, %205
%207 = load double*, double** %4
%208 = getelementptr inbounds double, double* %207, i64 1
store double %206, double* %208
%209 = load double, double* %13
%210 = load double, double* %15
%211 = load double*, double** %4
%212 = getelementptr inbounds double, double* %211, i64 2
%213 = load double, double* %212
%214 = fsub double %210, %213
%215 = fmul double %209, %214
%216 = load double*, double** %4
%217 = getelementptr inbounds double, double* %216, i64 2
store double %215, double* %217
%218 = load double*, double** %4
%219 = load i64, i64* %5
%220 = lshr i64 %219, 1
%221 = call i32 @four1(double* %218, i64 %220, i32 -1)
br label %222
222: ; preds = %197, %180
ret void
}

LLVM IR (-O2):
@M_PI = global double 0.000000e+00
define void @realft(double* %0, i64 %1, i32 %2) {
%4 = load double, double* @M_PI
%5 = lshr i64 %1, 1
%6 = uitofp i64 %5 to double
%7 = fdiv double %4, %6
%8 = icmp eq i32 %2, 1
br i1 %8, label %9, label %11
9: ; preds = %3
%10 = tail call i32 @four1(double* %0, i64 %5, i32 1)
br label %13
11: ; preds = %3
%12 = fneg double %7
br label %13
13: ; preds = %11, %9
%14 = phi double [ -5.000000e-01, %9 ], [ 5.000000e-01, %11 ]
%15 = phi double [ %7, %9 ], [ %12, %11 ]
%16 = fmul double %15, 5.000000e-01
%17 = tail call double @sin(double %16)
%18 = fmul double %17, -2.000000e+00
%19 = fmul double %17, %18
%20 = tail call double @sin(double %15)
%21 = add i64 %1, 3
%22 = icmp ult i64 %1, 8
br i1 %22, label %79, label %23
23: ; preds = %13
%24 = lshr i64 %1, 2
%25 = fadd double %19, 1.000000e+00
%26 = fneg double %14
%27 = insertelement <2 x double> poison, double %20, i64 0
%28 = insertelement <2 x double> %27, double %25, i64 1
%29 = insertelement <2 x double> poison, double %14, i64 0
%30 = insertelement <2 x double> %29, double %26, i64 1
%31 = insertelement <2 x double> poison, double %19, i64 0
%32 = shufflevector <2 x double> %31, <2 x double> poison, <2 x i32> zeroinitializer
%33 = shufflevector <2 x double> %27, <2 x double> poison, <2 x i32> zeroinitializer
br label %34
34: ; preds = %23, %34
%35 = phi i64 [ 2, %23 ], [ %77, %34 ]
%36 = phi <2 x double> [ %28, %23 ], [ %76, %34 ]
%37 = shl nuw i64 %35, 1
%38 = add nsw i64 %37, -1
%39 = sub i64 %21, %37
%40 = getelementptr inbounds double, double* %0, i64 %38
%41 = getelementptr inbounds double, double* %0, i64 %39
%42 = bitcast double* %40 to <2 x double>*
%43 = load <2 x double>, <2 x double>* %42
%44 = bitcast double* %41 to <2 x double>*
%45 = load <2 x double>, <2 x double>* %44
%46 = fadd <2 x double> %43, %45
%47 = fsub <2 x double> %43, %45
%48 = shufflevector <2 x double> %46, <2 x double> %47, <2 x i32> <i32 0, i32 3>
%49 = fmul <2 x double> %48, <double 5.000000e-01, double 5.000000e-01>
%50 = shufflevector <2 x double> %47, <2 x double> %46, <2 x i32> <i32 0, i32 3>
%51 = fmul <2 x double> %30, %50
%52 = extractelement <2 x double> %36, i64 0
%53 = fneg double %52
%54 = shufflevector <2 x double> %51, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%55 = extractelement <2 x double> %36, i64 1
%56 = shufflevector <2 x double> %36, <2 x double> undef, <2 x i32> <i32 1, i32 undef>
%57 = shufflevector <2 x double> %36, <2 x double> poison, <2 x i32> <i32 1, i32 1>
%58 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %57, <2 x double> %54, <2 x double> %49)
%59 = insertelement <2 x double> poison, double %53, i64 0
%60 = shufflevector <2 x double> %59, <2 x double> %36, <2 x i32> <i32 0, i32 2>
%61 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %60, <2 x double> %51, <2 x double> %58)
%62 = bitcast double* %40 to <2 x double>*
store <2 x double> %61, <2 x double>* %62
%63 = fneg double %55
%64 = extractelement <2 x double> %49, i64 1
%65 = fneg double %64
%66 = insertelement <2 x double> %36, double %63, i64 0
%67 = shufflevector <2 x double> %51, <2 x double> undef, <2 x i32> <i32 1, i32 0>
%68 = insertelement <2 x double> %49, double %65, i64 1
%69 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %66, <2 x double> %67, <2 x double> %68)
%70 = shufflevector <2 x double> %36, <2 x double> undef, <2 x i32> zeroinitializer
%71 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %70, <2 x double> %51, <2 x double> %69)
%72 = bitcast double* %41 to <2 x double>*
store <2 x double> %71, <2 x double>* %72
%73 = insertelement <2 x double> %56, double %53, i64 1
%74 = fmul <2 x double> %33, %73
%75 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %36, <2 x double> %32, <2 x double> %74)
%76 = fadd <2 x double> %36, %75
%77 = add nuw nsw i64 %35, 1
%78 = icmp eq i64 %35, %24
br i1 %78, label %79, label %34
79: ; preds = %34, %13
%80 = getelementptr inbounds double, double* %0, i64 1
%81 = load double, double* %80
%82 = getelementptr inbounds double, double* %0, i64 2
%83 = load double, double* %82
%84 = fadd double %81, %83
br i1 %8, label %85, label %87
85: ; preds = %79
store double %84, double* %80
%86 = fsub double %81, %83
store double %86, double* %82
br label %94
87: ; preds = %79
%88 = fsub double %81, %83
%89 = insertelement <2 x double> poison, double %84, i64 0
%90 = insertelement <2 x double> %89, double %88, i64 1
%91 = fmul <2 x double> %90, <double 5.000000e-01, double 5.000000e-01>
%92 = bitcast double* %80 to <2 x double>*
store <2 x double> %91, <2 x double>* %92
%93 = tail call i32 @four1(double* %0, i64 %5, i32 -1)
br label %94
94: ; preds = %87, %85
ret void
}