void filter_subband(z, s, sblimit) double z[512], s[32];
int sblimit;
{
  double yprime[32];
  int i, j;
  {
    yprime[0] = z[16];
    for (i = 1; i <= 16; i++)
      yprime[i] = z[i + 16] + z[16 - i];
    for (i = 17; i <= 31; i++)
      yprime[i] = z[i + 16] - z[80 - i];
    IDCT32(yprime, s, sblimit);
  }
}


x86 assembly (clang, -O0):
<filter_subband>:
push   %rbp
mov    %rsp,%rbp
sub    $0x130,%rsp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    %edx,-0x14(%rbp)
mov    -0x8(%rbp),%rax
movsd  0x80(%rax),%xmm0
movsd  %xmm0,-0x120(%rbp)
ff
movl   $0x1,-0x124(%rbp)
cmpl   $0x10,-0x124(%rbp)
jg     11a1 <filter_subband+0x91>
mov    -0x8(%rbp),%rax
mov    -0x124(%rbp),%ecx
add    $0x10,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x8(%rbp),%rax
mov    $0x10,%ecx
sub    -0x124(%rbp),%ecx
movslq %ecx,%rcx
addsd  (%rax,%rcx,8),%xmm0
movslq -0x124(%rbp),%rax
movsd  %xmm0,-0x120(%rbp,%rax,8)
ff ff
mov    -0x124(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x124(%rbp)
jmp    1144 <filter_subband+0x34>
movl   $0x11,-0x124(%rbp)
cmpl   $0x1f,-0x124(%rbp)
jg     1208 <filter_subband+0xf8>
mov    -0x8(%rbp),%rax
mov    -0x124(%rbp),%ecx
add    $0x10,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
mov    -0x8(%rbp),%rax
mov    $0x50,%ecx
sub    -0x124(%rbp),%ecx
movslq %ecx,%rcx
subsd  (%rax,%rcx,8),%xmm0
movslq -0x124(%rbp),%rax
movsd  %xmm0,-0x120(%rbp,%rax,8)
ff ff
mov    -0x124(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x124(%rbp)
jmp    11ab <filter_subband+0x9b>
lea    -0x120(%rbp),%rdi
mov    -0x10(%rbp),%rsi
mov    -0x14(%rbp),%edx
mov    $0x0,%al
call   1030 <IDCT32@plt>
add    $0x130,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<filter_subband>:
sub    $0x108,%rsp
movsd  0x80(%rdi),%xmm0
movsd  %xmm0,(%rsp)
movupd 0x70(%rdi),%xmm0
movupd 0x88(%rdi),%xmm1
shufpd $0x1,%xmm0,%xmm0
addpd  %xmm1,%xmm0
movupd %xmm0,0x8(%rsp)
movupd 0x60(%rdi),%xmm0
movupd 0x98(%rdi),%xmm1
shufpd $0x1,%xmm0,%xmm0
addpd  %xmm1,%xmm0
movupd %xmm0,0x18(%rsp)
movupd 0x50(%rdi),%xmm0
movupd 0xa8(%rdi),%xmm1
shufpd $0x1,%xmm0,%xmm0
addpd  %xmm1,%xmm0
movupd %xmm0,0x28(%rsp)
movupd 0x40(%rdi),%xmm0
movupd 0xb8(%rdi),%xmm1
shufpd $0x1,%xmm0,%xmm0
addpd  %xmm1,%xmm0
movupd %xmm0,0x38(%rsp)
movupd 0x30(%rdi),%xmm0
movupd 0xc8(%rdi),%xmm1
shufpd $0x1,%xmm0,%xmm0
addpd  %xmm1,%xmm0
movupd %xmm0,0x48(%rsp)
movupd 0x20(%rdi),%xmm0
movupd 0xd8(%rdi),%xmm1
shufpd $0x1,%xmm0,%xmm0
addpd  %xmm1,%xmm0
movupd %xmm0,0x58(%rsp)
movupd 0x10(%rdi),%xmm0
movupd 0xe8(%rdi),%xmm1
shufpd $0x1,%xmm0,%xmm0
addpd  %xmm1,%xmm0
movupd %xmm0,0x68(%rsp)
movupd (%rdi),%xmm0
movupd 0xf8(%rdi),%xmm1
shufpd $0x1,%xmm0,%xmm0
addpd  %xmm1,%xmm0
movupd %xmm0,0x78(%rsp)
movupd 0x108(%rdi),%xmm0
movupd 0x1f0(%rdi),%xmm1
shufpd $0x1,%xmm1,%xmm1
subpd  %xmm1,%xmm0
movupd %xmm0,0x88(%rsp)
movupd 0x118(%rdi),%xmm0
movupd 0x1e0(%rdi),%xmm1
shufpd $0x1,%xmm1,%xmm1
subpd  %xmm1,%xmm0
movupd %xmm0,0x98(%rsp)
movupd 0x128(%rdi),%xmm0
movupd 0x1d0(%rdi),%xmm1
shufpd $0x1,%xmm1,%xmm1
subpd  %xmm1,%xmm0
movupd %xmm0,0xa8(%rsp)
movupd 0x138(%rdi),%xmm0
movupd 0x1c0(%rdi),%xmm1
shufpd $0x1,%xmm1,%xmm1
subpd  %xmm1,%xmm0
movupd %xmm0,0xb8(%rsp)
movupd 0x148(%rdi),%xmm0
movupd 0x1b0(%rdi),%xmm1
shufpd $0x1,%xmm1,%xmm1
subpd  %xmm1,%xmm0
movupd %xmm0,0xc8(%rsp)
movupd 0x158(%rdi),%xmm0
movupd 0x1a0(%rdi),%xmm1
shufpd $0x1,%xmm1,%xmm1
subpd  %xmm1,%xmm0
movupd %xmm0,0xd8(%rsp)
movupd 0x168(%rdi),%xmm0
movupd 0x190(%rdi),%xmm1
shufpd $0x1,%xmm1,%xmm1
subpd  %xmm1,%xmm0
movupd %xmm0,0xe8(%rsp)
movsd  0x178(%rdi),%xmm0
subsd  0x188(%rdi),%xmm0
movsd  %xmm0,0xf8(%rsp)
mov    %rsp,%rdi
xor    %eax,%eax
call   1030 <IDCT32@plt>
add    $0x108,%rsp
ret

LLVM IR (-O0):
define void @filter_subband(double* %0, double* %1, i32 %2) {
%4 = alloca double*
%5 = alloca double*
%6 = alloca i32
%7 = alloca [32 x double]
%8 = alloca i32
%9 = alloca i32
store double* %0, double** %4
store double* %1, double** %5
store i32 %2, i32* %6
%10 = load double*, double** %4
%11 = getelementptr inbounds double, double* %10, i64 16
%12 = load double, double* %11
%13 = getelementptr inbounds [32 x double], [32 x double]* %7, i64 0, i64 0
store double %12, double* %13
store i32 1, i32* %8
br label %14
14: ; preds = %34, %3
%15 = load i32, i32* %8
%16 = icmp sle i32 %15, 16
br i1 %16, label %17, label %37
17: ; preds = %14
%18 = load double*, double** %4
%19 = load i32, i32* %8
%20 = add nsw i32 %19, 16
%21 = sext i32 %20 to i64
%22 = getelementptr inbounds double, double* %18, i64 %21
%23 = load double, double* %22
%24 = load double*, double** %4
%25 = load i32, i32* %8
%26 = sub nsw i32 16, %25
%27 = sext i32 %26 to i64
%28 = getelementptr inbounds double, double* %24, i64 %27
%29 = load double, double* %28
%30 = fadd double %23, %29
%31 = load i32, i32* %8
%32 = sext i32 %31 to i64
%33 = getelementptr inbounds [32 x double], [32 x double]* %7, i64 0, i64 %32
store double %30, double* %33
br label %34
34: ; preds = %17
%35 = load i32, i32* %8
%36 = add nsw i32 %35, 1
store i32 %36, i32* %8
br label %14
37: ; preds = %14
store i32 17, i32* %8
br label %38
38: ; preds = %58, %37
%39 = load i32, i32* %8
%40 = icmp sle i32 %39, 31
br i1 %40, label %41, label %61
41: ; preds = %38
%42 = load double*, double** %4
%43 = load i32, i32* %8
%44 = add nsw i32 %43, 16
%45 = sext i32 %44 to i64
%46 = getelementptr inbounds double, double* %42, i64 %45
%47 = load double, double* %46
%48 = load double*, double** %4
%49 = load i32, i32* %8
%50 = sub nsw i32 80, %49
%51 = sext i32 %50 to i64
%52 = getelementptr inbounds double, double* %48, i64 %51
%53 = load double, double* %52
%54 = fsub double %47, %53
%55 = load i32, i32* %8
%56 = sext i32 %55 to i64
%57 = getelementptr inbounds [32 x double], [32 x double]* %7, i64 0, i64 %56
store double %54, double* %57
br label %58
58: ; preds = %41
%59 = load i32, i32* %8
%60 = add nsw i32 %59, 1
store i32 %60, i32* %8
br label %38
61: ; preds = %38
%62 = getelementptr inbounds [32 x double], [32 x double]* %7, i64 0, i64 0
%63 = load double*, double** %5
%64 = load i32, i32* %6
%65 = call i32 (double*, double*, i32, ...) bitcast (i32 (...)* @IDCT32 to i32 (double*, double*, i32, ...)*)(double* %62, double* %63, i32 %64)
ret void
}

LLVM IR (-O2):
define void @filter_subband(double* nocapture %0, double* %1, i32 %2) {
%4 = alloca [32 x double]
%5 = bitcast [32 x double]* %4 to i8*
%6 = getelementptr inbounds double, double* %0, i64 16
%7 = load double, double* %6
%8 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 0
store double %7, double* %8
%9 = getelementptr inbounds double, double* %0, i64 17
%10 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 1
%11 = bitcast double* %9 to <2 x double>*
%12 = load <2 x double>, <2 x double>* %11
%13 = getelementptr inbounds double, double* %0, i64 14
%14 = bitcast double* %13 to <2 x double>*
%15 = load <2 x double>, <2 x double>* %14
%16 = shufflevector <2 x double> %15, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%17 = fadd <2 x double> %12, %16
%18 = bitcast double* %10 to <2 x double>*
store <2 x double> %17, <2 x double>* %18
%19 = getelementptr inbounds double, double* %0, i64 19
%20 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 3
%21 = bitcast double* %19 to <2 x double>*
%22 = load <2 x double>, <2 x double>* %21
%23 = getelementptr inbounds double, double* %0, i64 12
%24 = bitcast double* %23 to <2 x double>*
%25 = load <2 x double>, <2 x double>* %24
%26 = shufflevector <2 x double> %25, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%27 = fadd <2 x double> %22, %26
%28 = bitcast double* %20 to <2 x double>*
store <2 x double> %27, <2 x double>* %28
%29 = getelementptr inbounds double, double* %0, i64 21
%30 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 5
%31 = bitcast double* %29 to <2 x double>*
%32 = load <2 x double>, <2 x double>* %31
%33 = getelementptr inbounds double, double* %0, i64 10
%34 = bitcast double* %33 to <2 x double>*
%35 = load <2 x double>, <2 x double>* %34
%36 = shufflevector <2 x double> %35, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%37 = fadd <2 x double> %32, %36
%38 = bitcast double* %30 to <2 x double>*
store <2 x double> %37, <2 x double>* %38
%39 = getelementptr inbounds double, double* %0, i64 23
%40 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 7
%41 = bitcast double* %39 to <2 x double>*
%42 = load <2 x double>, <2 x double>* %41
%43 = getelementptr inbounds double, double* %0, i64 8
%44 = bitcast double* %43 to <2 x double>*
%45 = load <2 x double>, <2 x double>* %44
%46 = shufflevector <2 x double> %45, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%47 = fadd <2 x double> %42, %46
%48 = bitcast double* %40 to <2 x double>*
store <2 x double> %47, <2 x double>* %48
%49 = getelementptr inbounds double, double* %0, i64 25
%50 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 9
%51 = bitcast double* %49 to <2 x double>*
%52 = load <2 x double>, <2 x double>* %51
%53 = getelementptr inbounds double, double* %0, i64 6
%54 = bitcast double* %53 to <2 x double>*
%55 = load <2 x double>, <2 x double>* %54
%56 = shufflevector <2 x double> %55, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%57 = fadd <2 x double> %52, %56
%58 = bitcast double* %50 to <2 x double>*
store <2 x double> %57, <2 x double>* %58
%59 = getelementptr inbounds double, double* %0, i64 27
%60 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 11
%61 = bitcast double* %59 to <2 x double>*
%62 = load <2 x double>, <2 x double>* %61
%63 = getelementptr inbounds double, double* %0, i64 4
%64 = bitcast double* %63 to <2 x double>*
%65 = load <2 x double>, <2 x double>* %64
%66 = shufflevector <2 x double> %65, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%67 = fadd <2 x double> %62, %66
%68 = bitcast double* %60 to <2 x double>*
store <2 x double> %67, <2 x double>* %68
%69 = getelementptr inbounds double, double* %0, i64 29
%70 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 13
%71 = bitcast double* %69 to <2 x double>*
%72 = load <2 x double>, <2 x double>* %71
%73 = getelementptr inbounds double, double* %0, i64 2
%74 = bitcast double* %73 to <2 x double>*
%75 = load <2 x double>, <2 x double>* %74
%76 = shufflevector <2 x double> %75, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%77 = fadd <2 x double> %72, %76
%78 = bitcast double* %70 to <2 x double>*
store <2 x double> %77, <2 x double>* %78
%79 = getelementptr inbounds double, double* %0, i64 31
%80 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 15
%81 = bitcast double* %79 to <2 x double>*
%82 = load <2 x double>, <2 x double>* %81
%83 = bitcast double* %0 to <2 x double>*
%84 = load <2 x double>, <2 x double>* %83
%85 = shufflevector <2 x double> %84, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%86 = fadd <2 x double> %82, %85
%87 = bitcast double* %80 to <2 x double>*
store <2 x double> %86, <2 x double>* %87
%88 = getelementptr inbounds double, double* %0, i64 33
%89 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 17
%90 = bitcast double* %88 to <2 x double>*
%91 = load <2 x double>, <2 x double>* %90
%92 = getelementptr inbounds double, double* %0, i64 62
%93 = bitcast double* %92 to <2 x double>*
%94 = load <2 x double>, <2 x double>* %93
%95 = shufflevector <2 x double> %94, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%96 = fsub <2 x double> %91, %95
%97 = bitcast double* %89 to <2 x double>*
store <2 x double> %96, <2 x double>* %97
%98 = getelementptr inbounds double, double* %0, i64 35
%99 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 19
%100 = bitcast double* %98 to <2 x double>*
%101 = load <2 x double>, <2 x double>* %100
%102 = getelementptr inbounds double, double* %0, i64 60
%103 = bitcast double* %102 to <2 x double>*
%104 = load <2 x double>, <2 x double>* %103
%105 = shufflevector <2 x double> %104, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%106 = fsub <2 x double> %101, %105
%107 = bitcast double* %99 to <2 x double>*
store <2 x double> %106, <2 x double>* %107
%108 = getelementptr inbounds double, double* %0, i64 37
%109 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 21
%110 = bitcast double* %108 to <2 x double>*
%111 = load <2 x double>, <2 x double>* %110
%112 = getelementptr inbounds double, double* %0, i64 58
%113 = bitcast double* %112 to <2 x double>*
%114 = load <2 x double>, <2 x double>* %113
%115 = shufflevector <2 x double> %114, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%116 = fsub <2 x double> %111, %115
%117 = bitcast double* %109 to <2 x double>*
store <2 x double> %116, <2 x double>* %117
%118 = getelementptr inbounds double, double* %0, i64 39
%119 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 23
%120 = bitcast double* %118 to <2 x double>*
%121 = load <2 x double>, <2 x double>* %120
%122 = getelementptr inbounds double, double* %0, i64 56
%123 = bitcast double* %122 to <2 x double>*
%124 = load <2 x double>, <2 x double>* %123
%125 = shufflevector <2 x double> %124, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%126 = fsub <2 x double> %121, %125
%127 = bitcast double* %119 to <2 x double>*
store <2 x double> %126, <2 x double>* %127
%128 = getelementptr inbounds double, double* %0, i64 41
%129 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 25
%130 = bitcast double* %128 to <2 x double>*
%131 = load <2 x double>, <2 x double>* %130
%132 = getelementptr inbounds double, double* %0, i64 54
%133 = bitcast double* %132 to <2 x double>*
%134 = load <2 x double>, <2 x double>* %133
%135 = shufflevector <2 x double> %134, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%136 = fsub <2 x double> %131, %135
%137 = bitcast double* %129 to <2 x double>*
store <2 x double> %136, <2 x double>* %137
%138 = getelementptr inbounds double, double* %0, i64 43
%139 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 27
%140 = bitcast double* %138 to <2 x double>*
%141 = load <2 x double>, <2 x double>* %140
%142 = getelementptr inbounds double, double* %0, i64 52
%143 = bitcast double* %142 to <2 x double>*
%144 = load <2 x double>, <2 x double>* %143
%145 = shufflevector <2 x double> %144, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%146 = fsub <2 x double> %141, %145
%147 = bitcast double* %139 to <2 x double>*
store <2 x double> %146, <2 x double>* %147
%148 = getelementptr inbounds double, double* %0, i64 45
%149 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 29
%150 = bitcast double* %148 to <2 x double>*
%151 = load <2 x double>, <2 x double>* %150
%152 = getelementptr inbounds double, double* %0, i64 50
%153 = bitcast double* %152 to <2 x double>*
%154 = load <2 x double>, <2 x double>* %153
%155 = shufflevector <2 x double> %154, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%156 = fsub <2 x double> %151, %155
%157 = bitcast double* %149 to <2 x double>*
store <2 x double> %156, <2 x double>* %157
%158 = getelementptr inbounds double, double* %0, i64 47
%159 = load double, double* %158
%160 = getelementptr inbounds double, double* %0, i64 49
%161 = load double, double* %160
%162 = fsub double %159, %161
%163 = getelementptr inbounds [32 x double], [32 x double]* %4, i64 0, i64 31
store double %162, double* %163
%164 = call i32 (double*, double*, i32, ...) bitcast (i32 (...)* @IDCT32 to i32 (double*, double*, i32, ...)*)(double* %8, double* %1, i32 %2)
ret void
}