void mp_squh(int n, int radix, int in[], int out[], int nfft, double outfft[]) {
  void rdft(int n, int isgn, double *a);
  void mp_mul_i2d(int n, int radix, int nfft, int shift, int in[],
                  double dout[]);
  void mp_mul_csqu(int nfft, double dinout[]);
  void mp_mul_d2i(int n, int radix, int nfft, double din[], int out[]);
  mp_mul_i2d(n, radix, nfft, 0, in, outfft);
  rdft(nfft, 1, &outfft[1]);
  mp_mul_csqu(nfft, outfft);
  rdft(nfft, -1, &outfft[1]);
  mp_mul_d2i(n, radix, nfft, outfft, out);
}


x86 assembly (clang, -O0):
<mp_squh>:
push   %rbp
mov    %rsp,%rbp
sub    $0x30,%rsp
mov    %edi,-0x4(%rbp)
mov    %esi,-0x8(%rbp)
mov    %rdx,-0x10(%rbp)
mov    %rcx,-0x18(%rbp)
mov    %r8d,-0x1c(%rbp)
mov    %r9,-0x28(%rbp)
mov    -0x4(%rbp),%edi
mov    -0x8(%rbp),%esi
mov    -0x1c(%rbp),%edx
mov    -0x10(%rbp),%r8
mov    -0x28(%rbp),%r9
xor    %ecx,%ecx
call   1030 <mp_mul_i2d@plt>
mov    -0x1c(%rbp),%edi
mov    -0x28(%rbp),%rdx
add    $0x8,%rdx
mov    $0x1,%esi
call   1050 <rdft@plt>
mov    -0x1c(%rbp),%edi
mov    -0x28(%rbp),%rsi
call   1040 <mp_mul_csqu@plt>
mov    -0x1c(%rbp),%edi
mov    -0x28(%rbp),%rdx
add    $0x8,%rdx
mov    $0xffffffff,%esi
call   1050 <rdft@plt>
mov    -0x4(%rbp),%edi
mov    -0x8(%rbp),%esi
mov    -0x1c(%rbp),%edx
mov    -0x28(%rbp),%rcx
mov    -0x18(%rbp),%r8
call   1060 <mp_mul_d2i@plt>
add    $0x30,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<mp_squh>:
push   %rbp
push   %r15
push   %r14
push   %r13
push   %r12
push   %rbx
push   %rax
mov    %r9,%rbx
mov    %r8d,%ebp
mov    %rcx,%r14
mov    %rdx,%r8
mov    %esi,%r15d
mov    %edi,%r12d
mov    %ebp,%edx
xor    %ecx,%ecx
call   1030 <mp_mul_i2d@plt>
lea    0x8(%rbx),%r13
mov    %ebp,%edi
mov    $0x1,%esi
mov    %r13,%rdx
call   1050 <rdft@plt>
mov    %ebp,%edi
mov    %rbx,%rsi
call   1040 <mp_mul_csqu@plt>
mov    %ebp,%edi
mov    $0xffffffff,%esi
mov    %r13,%rdx
call   1050 <rdft@plt>
mov    %r12d,%edi
mov    %r15d,%esi
mov    %ebp,%edx
mov    %rbx,%rcx
mov    %r14,%r8
add    $0x8,%rsp
pop    %rbx
pop    %r12
pop    %r13
pop    %r14
pop    %r15
pop    %rbp
jmp    1060 <mp_mul_d2i@plt>

LLVM IR (-O0):
define void @mp_squh(i32 %0, i32 %1, i32* %2, i32* %3, i32 %4, double* %5) {
%7 = alloca i32
%8 = alloca i32
%9 = alloca i32*
%10 = alloca i32*
%11 = alloca i32
%12 = alloca double*
store i32 %0, i32* %7
store i32 %1, i32* %8
store i32* %2, i32** %9
store i32* %3, i32** %10
store i32 %4, i32* %11
store double* %5, double** %12
%13 = load i32, i32* %7
%14 = load i32, i32* %8
%15 = load i32, i32* %11
%16 = load i32*, i32** %9
%17 = load double*, double** %12
%18 = load i32, i32* %11
%19 = load double*, double** %12
%20 = getelementptr inbounds double, double* %19, i64 1
%21 = load i32, i32* %11
%22 = load double*, double** %12
%23 = load i32, i32* %11
%24 = load double*, double** %12
%25 = getelementptr inbounds double, double* %24, i64 1
%26 = load i32, i32* %7
%27 = load i32, i32* %8
%28 = load i32, i32* %11
%29 = load double*, double** %12
%30 = load i32*, i32** %10
ret void
}

LLVM IR (-O2):
define void @mp_squh(i32 %0, i32 %1, i32* %2, i32* %3, i32 %4, double* %5) {
tail call void @mp_mul_i2d(i32 %0, i32 %1, i32 %4, i32 0, i32* %2, double* %5)
%7 = getelementptr inbounds double, double* %5, i64 1
tail call void @rdft(i32 %4, i32 1, double* %7)
tail call void @mp_mul_csqu(i32 %4, double* %5)
tail call void @rdft(i32 %4, i32 -1, double* %7)
tail call void @mp_mul_d2i(i32 %0, i32 %1, i32 %4, double* %5, i32* %3)
ret void
}