void ZVaxpy11(int n, double y0[], double alpha[], double x0[]) {
  register double ar00;
  register double ai00;
  register double xr0i;
  register double xi0i;
  int ii;
  ar00 = alpha[0];
  ai00 = alpha[1];
  for (ii = 0; ii < n; ii++) {
    xr0i = x0[2 * ii];
    xi0i = x0[2 * ii + 1];
    y0[2 * ii] += (ar00 * xr0i - ai00 * xi0i);
    y0[2 * ii + 1] += (ar00 * xi0i + ai00 * xr0i);
  }
  return;
}


x86 assembly (clang, -O0):
<ZVaxpy11>:
push   %rbp
mov    %rsp,%rbp
mov    %edi,-0x4(%rbp)
mov    %rsi,-0x10(%rbp)
mov    %rdx,-0x18(%rbp)
mov    %rcx,-0x20(%rbp)
mov    -0x18(%rbp),%rax
movsd  (%rax),%xmm0
movsd  %xmm0,-0x28(%rbp)
mov    -0x18(%rbp),%rax
movsd  0x8(%rax),%xmm0
movsd  %xmm0,-0x30(%rbp)
movl   $0x0,-0x44(%rbp)
mov    -0x44(%rbp),%eax
cmp    -0x4(%rbp),%eax
jge    1200 <ZVaxpy11+0x100>
mov    -0x20(%rbp),%rax
mov    -0x44(%rbp),%ecx
shl    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x38(%rbp)
mov    -0x20(%rbp),%rax
mov    -0x44(%rbp),%ecx
shl    $0x1,%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
movsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x40(%rbp)
movsd  -0x28(%rbp),%xmm0
movsd  -0x38(%rbp),%xmm2
movsd  -0x30(%rbp),%xmm1
mulsd  -0x40(%rbp),%xmm1
movq   %xmm1,%rax
movabs $0x8000000000000000,%rcx
xor    %rcx,%rax
movq   %rax,%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x10(%rbp),%rax
mov    -0x44(%rbp),%ecx
shl    $0x1,%ecx
movslq %ecx,%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,(%rax,%rcx,8)
movsd  -0x28(%rbp),%xmm0
movsd  -0x40(%rbp),%xmm2
movsd  -0x30(%rbp),%xmm1
mulsd  -0x38(%rbp),%xmm1
mulsd  %xmm2,%xmm0
addsd  %xmm1,%xmm0
mov    -0x10(%rbp),%rax
mov    -0x44(%rbp),%ecx
shl    $0x1,%ecx
add    $0x1,%ecx
movslq %ecx,%rcx
addsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x44(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x44(%rbp)
jmp    1135 <ZVaxpy11+0x35>
pop    %rbp
ret

x86 assembly (clang, -O2):
<ZVaxpy11>:
test   %edi,%edi
jle    12d2 <ZVaxpy11+0x1d2>
movsd  (%rdx),%xmm11
movsd  0x8(%rdx),%xmm1
movapd 0xee5(%rip),%xmm8
xorpd  %xmm1,%xmm8
mov    %edi,%r8d
cmp    $0x1,%edi
je     1148 <ZVaxpy11+0x48>
mov    %r8,%rax
shl    $0x4,%rax
lea    (%rcx,%rax,1),%rdx
cmp    %rsi,%rdx
jbe    1224 <ZVaxpy11+0x124>
add    %rsi,%rax
cmp    %rcx,%rax
jbe    1224 <ZVaxpy11+0x124>
xor    %edx,%edx
mov    %rdx,%rax
not    %rax
test   $0x1,%r8b
je     1198 <ZVaxpy11+0x98>
mov    %rdx,%rdi
shl    $0x4,%rdi
movupd (%rcx,%rdi,1),%xmm0
movapd %xmm8,%xmm2
unpcklpd %xmm1,%xmm2
movapd %xmm11,%xmm3
unpcklpd %xmm11,%xmm3
mulpd  %xmm0,%xmm3
shufpd $0x1,%xmm0,%xmm0
mulpd  %xmm2,%xmm0
addpd  %xmm0,%xmm3
movupd (%rsi,%rdi,1),%xmm0
addpd  %xmm3,%xmm0
movupd %xmm0,(%rsi,%rdi,1)
or     $0x1,%rdx
add    %r8,%rax
je     12d2 <ZVaxpy11+0x1d2>
unpcklpd %xmm8,%xmm1
unpcklpd %xmm11,%xmm11
sub    %rdx,%r8
shl    $0x4,%rdx
add    $0x10,%rdx
cs nopw 0x0(%rax,%rax,1)
movupd -0x10(%rcx,%rdx,1),%xmm0
movapd %xmm0,%xmm2
mulpd  %xmm1,%xmm2
shufpd $0x1,%xmm2,%xmm2
mulpd  %xmm11,%xmm0
addpd  %xmm2,%xmm0
movupd -0x10(%rsi,%rdx,1),%xmm2
addpd  %xmm0,%xmm2
movupd (%rsi,%rdx,1),%xmm0
movupd %xmm2,-0x10(%rsi,%rdx,1)
movupd (%rcx,%rdx,1),%xmm2
movapd %xmm2,%xmm3
mulpd  %xmm1,%xmm3
shufpd $0x1,%xmm3,%xmm3
mulpd  %xmm11,%xmm2
addpd  %xmm3,%xmm2
addpd  %xmm0,%xmm2
movupd %xmm2,(%rsi,%rdx,1)
add    $0x20,%rdx
add    $0xfffffffffffffffe,%r8
jne    11c0 <ZVaxpy11+0xc0>
jmp    12d2 <ZVaxpy11+0x1d2>
mov    %r8d,%edx
and    $0xfffffffe,%edx
movapd %xmm8,%xmm9
unpcklpd %xmm8,%xmm9
movapd %xmm11,%xmm0
unpcklpd %xmm11,%xmm0
movapd %xmm1,%xmm10
unpcklpd %xmm1,%xmm10
xor    %edi,%edi
mov    %rdx,%rax
nopl   (%rax)
movupd (%rcx,%rdi,1),%xmm2
movupd 0x10(%rcx,%rdi,1),%xmm7
movapd %xmm2,%xmm6
unpcklpd %xmm7,%xmm6
unpckhpd %xmm7,%xmm2
movapd %xmm0,%xmm7
mulpd  %xmm2,%xmm7
mulpd  %xmm9,%xmm2
movapd %xmm0,%xmm4
mulpd  %xmm6,%xmm4
addpd  %xmm2,%xmm4
movupd (%rsi,%rdi,1),%xmm3
movupd 0x10(%rsi,%rdi,1),%xmm5
movapd %xmm3,%xmm2
unpcklpd %xmm5,%xmm2
addpd  %xmm4,%xmm2
unpckhpd %xmm5,%xmm3
mulpd  %xmm10,%xmm6
addpd  %xmm7,%xmm6
addpd  %xmm3,%xmm6
movapd %xmm2,%xmm3
unpckhpd %xmm6,%xmm3
unpcklpd %xmm6,%xmm2
movupd %xmm2,(%rsi,%rdi,1)
movupd %xmm3,0x10(%rsi,%rdi,1)
add    $0x20,%rdi
add    $0xfffffffffffffffe,%rax
jne    1250 <ZVaxpy11+0x150>
cmp    %r8,%rdx
jne    114a <ZVaxpy11+0x4a>
ret

LLVM IR (-O0):
define void @ZVaxpy11(i32 %0, double* %1, double* %2, double* %3) {
%5 = alloca i32
%6 = alloca double*
%7 = alloca double*
%8 = alloca double*
%9 = alloca double
%10 = alloca double
%11 = alloca double
%12 = alloca double
%13 = alloca i32
store i32 %0, i32* %5
store double* %1, double** %6
store double* %2, double** %7
store double* %3, double** %8
%14 = load double*, double** %7
%15 = getelementptr inbounds double, double* %14, i64 0
%16 = load double, double* %15
store double %16, double* %9
%17 = load double*, double** %7
%18 = getelementptr inbounds double, double* %17, i64 1
%19 = load double, double* %18
store double %19, double* %10
store i32 0, i32* %13
br label %20
20: ; preds = %66, %4
%21 = load i32, i32* %13
%22 = load i32, i32* %5
%23 = icmp slt i32 %21, %22
br i1 %23, label %24, label %69
24: ; preds = %20
%25 = load double*, double** %8
%26 = load i32, i32* %13
%27 = mul nsw i32 2, %26
%28 = sext i32 %27 to i64
%29 = getelementptr inbounds double, double* %25, i64 %28
%30 = load double, double* %29
store double %30, double* %11
%31 = load double*, double** %8
%32 = load i32, i32* %13
%33 = mul nsw i32 2, %32
%34 = add nsw i32 %33, 1
%35 = sext i32 %34 to i64
%36 = getelementptr inbounds double, double* %31, i64 %35
%37 = load double, double* %36
store double %37, double* %12
%38 = load double, double* %9
%39 = load double, double* %11
%40 = load double, double* %10
%41 = load double, double* %12
%42 = fmul double %40, %41
%43 = fneg double %42
%44 = call double @llvm.fmuladd.f64(double %38, double %39, double %43)
%45 = load double*, double** %6
%46 = load i32, i32* %13
%47 = mul nsw i32 2, %46
%48 = sext i32 %47 to i64
%49 = getelementptr inbounds double, double* %45, i64 %48
%50 = load double, double* %49
%51 = fadd double %50, %44
store double %51, double* %49
%52 = load double, double* %9
%53 = load double, double* %12
%54 = load double, double* %10
%55 = load double, double* %11
%56 = fmul double %54, %55
%57 = call double @llvm.fmuladd.f64(double %52, double %53, double %56)
%58 = load double*, double** %6
%59 = load i32, i32* %13
%60 = mul nsw i32 2, %59
%61 = add nsw i32 %60, 1
%62 = sext i32 %61 to i64
%63 = getelementptr inbounds double, double* %58, i64 %62
%64 = load double, double* %63
%65 = fadd double %64, %57
store double %65, double* %63
br label %66
66: ; preds = %24
%67 = load i32, i32* %13
%68 = add nsw i32 %67, 1
store i32 %68, i32* %13
br label %20
69: ; preds = %20
ret void
}

LLVM IR (-O2):
define void @ZVaxpy11(i32 %0, double* nocapture %1, double* nocapture %2, double* nocapture %3) {
%5 = load double, double* %2
%6 = getelementptr inbounds double, double* %2, i64 1
%7 = load double, double* %6
%8 = icmp sgt i32 %0, 0
br i1 %8, label %9, label %121
9: ; preds = %4
%10 = fneg double %7
%11 = zext i32 %0 to i64
%12 = icmp eq i32 %0, 1
br i1 %12, label %56, label %13
13: ; preds = %9
%14 = shl nuw nsw i64 %11, 1
%15 = getelementptr double, double* %1, i64 %14
%16 = getelementptr double, double* %3, i64 %14
%17 = icmp ugt double* %16, %1
%18 = icmp ugt double* %15, %3
%19 = and i1 %17, %18
br i1 %19, label %56, label %20
20: ; preds = %13
%21 = and i64 %11, 4294967294
%22 = insertelement <2 x double> poison, double %10, i64 0
%23 = shufflevector <2 x double> %22, <2 x double> poison, <2 x i32> zeroinitializer
%24 = insertelement <2 x double> poison, double %5, i64 0
%25 = shufflevector <2 x double> %24, <2 x double> poison, <2 x i32> zeroinitializer
%26 = insertelement <2 x double> poison, double %7, i64 0
%27 = shufflevector <2 x double> %26, <2 x double> poison, <2 x i32> zeroinitializer
%28 = getelementptr inbounds double, double* %1, i64 -1
br label %29
29: ; preds = %29, %20
%30 = phi i64 [ 0, %20 ], [ %52, %29 ]
%31 = shl nuw nsw i64 %30, 1
%32 = getelementptr inbounds double, double* %3, i64 %31
%33 = bitcast double* %32 to <4 x double>*
%34 = load <4 x double>, <4 x double>* %33
%35 = shufflevector <4 x double> %34, <4 x double> poison, <2 x i32> <i32 0, i32 2>
%36 = shufflevector <4 x double> %34, <4 x double> poison, <2 x i32> <i32 1, i32 3>
%37 = or i64 %31, 1
%38 = fmul <2 x double> %36, %23
%39 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %25, <2 x double> %35, <2 x double> %38)
%40 = getelementptr inbounds double, double* %1, i64 %31
%41 = bitcast double* %40 to <4 x double>*
%42 = load <4 x double>, <4 x double>* %41
%43 = shufflevector <4 x double> %42, <4 x double> poison, <2 x i32> <i32 0, i32 2>
%44 = shufflevector <4 x double> %42, <4 x double> poison, <2 x i32> <i32 1, i32 3>
%45 = fadd <2 x double> %43, %39
%46 = fmul <2 x double> %27, %35
%47 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %25, <2 x double> %36, <2 x double> %46)
%48 = fadd <2 x double> %47, %44
%49 = getelementptr inbounds double, double* %28, i64 %37
%50 = bitcast double* %49 to <4 x double>*
%51 = shufflevector <2 x double> %45, <2 x double> %48, <4 x i32> <i32 0, i32 2, i32 1, i32 3>
store <4 x double> %51, <4 x double>* %50
%52 = add nuw i64 %30, 2
%53 = icmp eq i64 %52, %21
br i1 %53, label %54, label %29
54: ; preds = %29
%55 = icmp eq i64 %21, %11
br i1 %55, label %121, label %56
56: ; preds = %13, %9, %54
%57 = phi i64 [ 0, %13 ], [ 0, %9 ], [ %21, %54 ]
%58 = xor i64 %57, -1
%59 = and i64 %11, 1
%60 = icmp eq i64 %59, 0
br i1 %60, label %79, label %61
61: ; preds = %56
%62 = shl nuw nsw i64 %57, 1
%63 = getelementptr inbounds double, double* %3, i64 %62
%64 = bitcast double* %63 to <2 x double>*
%65 = load <2 x double>, <2 x double>* %64
%66 = getelementptr inbounds double, double* %1, i64 %62
%67 = insertelement <2 x double> poison, double %7, i64 0
%68 = insertelement <2 x double> %67, double %10, i64 1
%69 = fmul <2 x double> %65, %68
%70 = shufflevector <2 x double> %69, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%71 = insertelement <2 x double> poison, double %5, i64 0
%72 = shufflevector <2 x double> %71, <2 x double> poison, <2 x i32> zeroinitializer
%73 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %72, <2 x double> %65, <2 x double> %70)
%74 = bitcast double* %66 to <2 x double>*
%75 = load <2 x double>, <2 x double>* %74
%76 = fadd <2 x double> %75, %73
%77 = bitcast double* %66 to <2 x double>*
store <2 x double> %76, <2 x double>* %77
%78 = or i64 %57, 1
br label %79
79: ; preds = %61, %56
%80 = phi i64 [ %57, %56 ], [ %78, %61 ]
%81 = sub nsw i64 0, %11
%82 = icmp eq i64 %58, %81
br i1 %82, label %121, label %83
83: ; preds = %79
%84 = insertelement <2 x double> poison, double %7, i64 0
%85 = insertelement <2 x double> %84, double %10, i64 1
%86 = insertelement <2 x double> poison, double %5, i64 0
%87 = shufflevector <2 x double> %86, <2 x double> poison, <2 x i32> zeroinitializer
%88 = insertelement <2 x double> poison, double %7, i64 0
%89 = insertelement <2 x double> %88, double %10, i64 1
%90 = insertelement <2 x double> poison, double %5, i64 0
%91 = shufflevector <2 x double> %90, <2 x double> poison, <2 x i32> zeroinitializer
br label %92
92: ; preds = %92, %83
%93 = phi i64 [ %80, %83 ], [ %119, %92 ]
%94 = shl nuw nsw i64 %93, 1
%95 = getelementptr inbounds double, double* %3, i64 %94
%96 = bitcast double* %95 to <2 x double>*
%97 = load <2 x double>, <2 x double>* %96
%98 = getelementptr inbounds double, double* %1, i64 %94
%99 = fmul <2 x double> %97, %85
%100 = shufflevector <2 x double> %99, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%101 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %87, <2 x double> %97, <2 x double> %100)
%102 = bitcast double* %98 to <2 x double>*
%103 = load <2 x double>, <2 x double>* %102
%104 = fadd <2 x double> %103, %101
%105 = bitcast double* %98 to <2 x double>*
store <2 x double> %104, <2 x double>* %105
%106 = shl i64 %93, 1
%107 = add i64 %106, 2
%108 = getelementptr inbounds double, double* %3, i64 %107
%109 = bitcast double* %108 to <2 x double>*
%110 = load <2 x double>, <2 x double>* %109
%111 = getelementptr inbounds double, double* %1, i64 %107
%112 = fmul <2 x double> %110, %89
%113 = shufflevector <2 x double> %112, <2 x double> poison, <2 x i32> <i32 1, i32 0>
%114 = call <2 x double> @llvm.fmuladd.v2f64(<2 x double> %91, <2 x double> %110, <2 x double> %113)
%115 = bitcast double* %111 to <2 x double>*
%116 = load <2 x double>, <2 x double>* %115
%117 = fadd <2 x double> %116, %114
%118 = bitcast double* %111 to <2 x double>*
store <2 x double> %117, <2 x double>* %118
%119 = add nuw nsw i64 %93, 2
%120 = icmp eq i64 %119, %11
br i1 %120, label %121, label %92
121: ; preds = %79, %92, %54, %4
ret void
}