void filt64(double *to, double *in, double dly) {
  int i;
  double x, z = (1.0 - dly) / (1.0 + dly), x1 = 0.0, y1 = 0.0;
  for (i = 0; i < 64; i++)
    x = in[i], to[i] = y1 = z * (x - y1) + x1, x1 = x;
}


x86 assembly (clang, -O0):
<filt64>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
movsd  %xmm0,-0x18(%rbp)
movsd  0xee7(%rip),%xmm0
subsd  -0x18(%rbp),%xmm0
movsd  0xeda(%rip),%xmm1
addsd  -0x18(%rbp),%xmm1
divsd  %xmm1,%xmm0
movsd  %xmm0,-0x30(%rbp)
xorps  %xmm0,%xmm0
movsd  %xmm0,-0x38(%rbp)
xorps  %xmm0,%xmm0
movsd  %xmm0,-0x40(%rbp)
movl   $0x0,-0x1c(%rbp)
cmpl   $0x40,-0x1c(%rbp)
jge    11ad <filt64+0xad>
mov    -0x10(%rbp),%rax
movslq -0x1c(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x28(%rbp)
movsd  -0x30(%rbp),%xmm0
movsd  -0x28(%rbp),%xmm2
subsd  -0x40(%rbp),%xmm2
movsd  -0x38(%rbp),%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
movsd  %xmm0,-0x40(%rbp)
mov    -0x8(%rbp),%rax
movslq -0x1c(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x28(%rbp),%xmm0
movsd  %xmm0,-0x38(%rbp)
mov    -0x1c(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x1c(%rbp)
jmp    114b <filt64+0x4b>
pop    %rbp
ret

x86 assembly (clang, -O2):
<filt64>:
movsd  0xef8(%rip),%xmm2
movapd %xmm2,%xmm1
subsd  %xmm0,%xmm1
addsd  %xmm2,%xmm0
divsd  %xmm0,%xmm1
xorpd  %xmm0,%xmm0
xor    %eax,%eax
xorpd  %xmm2,%xmm2
cs nopw 0x0(%rax,%rax,1)
nopl   0x0(%rax)
movsd  (%rsi,%rax,8),%xmm3
movapd %xmm3,%xmm4
subsd  %xmm0,%xmm4
mulsd  %xmm1,%xmm4
addsd  %xmm2,%xmm4
movsd  %xmm4,(%rdi,%rax,8)
movsd  0x8(%rsi,%rax,8),%xmm2
movapd %xmm2,%xmm0
subsd  %xmm4,%xmm0
mulsd  %xmm1,%xmm0
addsd  %xmm3,%xmm0
movsd  %xmm0,0x8(%rdi,%rax,8)
add    $0x2,%rax
cmp    $0x40,%rax
jne    1130 <filt64+0x30>
ret

LLVM IR (-O0):
define void @filt64(double* %0, double* %1, double %2) {
%4 = alloca double*
%5 = alloca double*
%6 = alloca double
%7 = alloca i32
%8 = alloca double
%9 = alloca double
%10 = alloca double
%11 = alloca double
store double* %0, double** %4
store double* %1, double** %5
store double %2, double* %6
%12 = load double, double* %6
%13 = fsub double 1.000000e+00, %12
%14 = load double, double* %6
%15 = fadd double 1.000000e+00, %14
%16 = fdiv double %13, %15
store double %16, double* %9
store double 0.000000e+00, double* %10
store double 0.000000e+00, double* %11
store i32 0, i32* %7
br label %17
17: ; preds = %37, %3
%18 = load i32, i32* %7
%19 = icmp slt i32 %18, 64
br i1 %19, label %20, label %40
20: ; preds = %17
%21 = load double*, double** %5
%22 = load i32, i32* %7
%23 = sext i32 %22 to i64
%24 = getelementptr inbounds double, double* %21, i64 %23
%25 = load double, double* %24
store double %25, double* %8
%26 = load double, double* %9
%27 = load double, double* %8
%28 = load double, double* %11
%29 = fsub double %27, %28
%30 = load double, double* %10
%31 = call double @llvm.fmuladd.f64(double %26, double %29, double %30)
store double %31, double* %11
%32 = load double*, double** %4
%33 = load i32, i32* %7
%34 = sext i32 %33 to i64
%35 = getelementptr inbounds double, double* %32, i64 %34
store double %31, double* %35
%36 = load double, double* %8
store double %36, double* %10
br label %37
37: ; preds = %20
%38 = load i32, i32* %7
%39 = add nsw i32 %38, 1
store i32 %39, i32* %7
br label %17
40: ; preds = %17
ret void
}

LLVM IR (-O2):
define void @filt64(double* nocapture writeonly %0, double* nocapture %1, double %2) {
%4 = fsub double 1.000000e+00, %2
%5 = fadd double %2, 1.000000e+00
%6 = fdiv double %4, %5
br label %7
7: ; preds = %7, %3
%8 = phi i64 [ 0, %3 ], [ %22, %7 ]
%9 = phi double [ 0.000000e+00, %3 ], [ %20, %7 ]
%10 = phi double [ 0.000000e+00, %3 ], [ %18, %7 ]
%11 = getelementptr inbounds double, double* %1, i64 %8
%12 = load double, double* %11
%13 = fsub double %12, %9
%14 = tail call double @llvm.fmuladd.f64(double %6, double %13, double %10)
%15 = getelementptr inbounds double, double* %0, i64 %8
store double %14, double* %15
%16 = or i64 %8, 1
%17 = getelementptr inbounds double, double* %1, i64 %16
%18 = load double, double* %17
%19 = fsub double %18, %14
%20 = tail call double @llvm.fmuladd.f64(double %6, double %19, double %12)
%21 = getelementptr inbounds double, double* %0, i64 %16
store double %20, double* %21
%22 = add nuw nsw i64 %8, 2
%23 = icmp eq i64 %22, 64
br i1 %23, label %24, label %7
24: ; preds = %7
ret void
}