void computePostCollisionDistributions(double *currentCell,
                                       const double *const tau,
                                       const double *const feq) {
  int i;
  double fi;
  for (i = 0; i < 19; i++) {
    fi = currentCell[i];
    currentCell[i] = fi - (fi - feq[i]) / *tau;
  }
}


x86 assembly (clang, -O0):
<computePostCollisionDistributions>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
mov    %rdx,-0x18(%rbp)
movl   $0x0,-0x1c(%rbp)
cmpl   $0x13,-0x1c(%rbp)
jge    1171 <computePostCollisionDistributions+0x71>
mov    -0x8(%rbp),%rax
movslq -0x1c(%rbp),%rcx
movsd  (%rax,%rcx,8),%xmm0
movsd  %xmm0,-0x28(%rbp)
movsd  -0x28(%rbp),%xmm0
movsd  -0x28(%rbp),%xmm1
mov    -0x18(%rbp),%rax
movslq -0x1c(%rbp),%rcx
subsd  (%rax,%rcx,8),%xmm1
mov    -0x10(%rbp),%rax
divsd  (%rax),%xmm1
subsd  %xmm1,%xmm0
mov    -0x8(%rbp),%rax
movslq -0x1c(%rbp),%rcx
movsd  %xmm0,(%rax,%rcx,8)
mov    -0x1c(%rbp),%eax
add    $0x1,%eax
mov    %eax,-0x1c(%rbp)
jmp    1117 <computePostCollisionDistributions+0x17>
pop    %rbp
ret

x86 assembly (clang, -O2):
<computePostCollisionDistributions>:
lea    0x98(%rdi),%rax
lea    0x98(%rdx),%rcx
lea    0x8(%rsi),%r8
cmp    %rdi,%rcx
seta   %r9b
cmp    %rdx,%rax
seta   %cl
and    %r9b,%cl
cmp    %rdi,%r8
seta   %r8b
cmp    %rsi,%rax
seta   %al
and    %r8b,%al
or     %cl,%al
je     113d <computePostCollisionDistributions+0x3d>
xor    %ecx,%ecx
jmp    12a7 <computePostCollisionDistributions+0x1a7>
movupd (%rdx),%xmm2
movupd (%rdi),%xmm3
movupd 0x10(%rdi),%xmm4
movupd 0x20(%rdi),%xmm1
movupd 0x30(%rdi),%xmm0
movapd %xmm3,%xmm5
subpd  %xmm2,%xmm5
movsd  (%rsi),%xmm2
unpcklpd %xmm2,%xmm2
divpd  %xmm2,%xmm5
subpd  %xmm5,%xmm3
movupd %xmm3,(%rdi)
movupd 0x10(%rdx),%xmm2
movapd %xmm4,%xmm3
subpd  %xmm2,%xmm3
movsd  (%rsi),%xmm2
unpcklpd %xmm2,%xmm2
divpd  %xmm2,%xmm3
subpd  %xmm3,%xmm4
movupd %xmm4,0x10(%rdi)
movupd 0x20(%rdx),%xmm2
movapd %xmm1,%xmm3
subpd  %xmm2,%xmm3
movsd  (%rsi),%xmm2
unpcklpd %xmm2,%xmm2
divpd  %xmm2,%xmm3
subpd  %xmm3,%xmm1
movupd %xmm1,0x20(%rdi)
movupd 0x30(%rdx),%xmm1
movapd %xmm0,%xmm2
subpd  %xmm1,%xmm2
movsd  (%rsi),%xmm1
unpcklpd %xmm1,%xmm1
divpd  %xmm1,%xmm2
subpd  %xmm2,%xmm0
movupd %xmm0,0x30(%rdi)
movupd 0x40(%rdi),%xmm0
movupd 0x40(%rdx),%xmm1
movapd %xmm0,%xmm2
subpd  %xmm1,%xmm2
movsd  (%rsi),%xmm1
unpcklpd %xmm1,%xmm1
divpd  %xmm1,%xmm2
subpd  %xmm2,%xmm0
movupd %xmm0,0x40(%rdi)
movupd 0x50(%rdi),%xmm0
movupd 0x50(%rdx),%xmm1
movapd %xmm0,%xmm2
subpd  %xmm1,%xmm2
movsd  (%rsi),%xmm1
unpcklpd %xmm1,%xmm1
divpd  %xmm1,%xmm2
subpd  %xmm2,%xmm0
movupd %xmm0,0x50(%rdi)
movupd 0x60(%rdi),%xmm0
movupd 0x60(%rdx),%xmm1
movapd %xmm0,%xmm2
subpd  %xmm1,%xmm2
movsd  (%rsi),%xmm1
unpcklpd %xmm1,%xmm1
divpd  %xmm1,%xmm2
subpd  %xmm2,%xmm0
movupd %xmm0,0x60(%rdi)
movupd 0x70(%rdi),%xmm0
movupd 0x70(%rdx),%xmm1
movapd %xmm0,%xmm2
subpd  %xmm1,%xmm2
movsd  (%rsi),%xmm1
unpcklpd %xmm1,%xmm1
divpd  %xmm1,%xmm2
subpd  %xmm2,%xmm0
movupd %xmm0,0x70(%rdi)
movupd 0x80(%rdi),%xmm0
movupd 0x80(%rdx),%xmm1
movapd %xmm0,%xmm2
subpd  %xmm1,%xmm2
movsd  (%rsi),%xmm1
unpcklpd %xmm1,%xmm1
divpd  %xmm1,%xmm2
subpd  %xmm2,%xmm0
movupd %xmm0,0x80(%rdi)
mov    $0x12,%ecx
movsd  (%rdi,%rcx,8),%xmm0
movapd %xmm0,%xmm1
subsd  (%rdx,%rcx,8),%xmm1
divsd  (%rsi),%xmm1
subsd  %xmm1,%xmm0
movsd  %xmm0,(%rdi,%rcx,8)
test   %al,%al
je     1313 <computePostCollisionDistributions+0x213>
add    $0x2,%rcx
nopw   0x0(%rax,%rax,1)
movsd  -0x8(%rdi,%rcx,8),%xmm0
movsd  (%rdi,%rcx,8),%xmm1
movapd %xmm0,%xmm2
subsd  -0x8(%rdx,%rcx,8),%xmm2
divsd  (%rsi),%xmm2
subsd  %xmm2,%xmm0
movsd  %xmm0,-0x8(%rdi,%rcx,8)
movapd %xmm1,%xmm0
subsd  (%rdx,%rcx,8),%xmm0
divsd  (%rsi),%xmm0
subsd  %xmm0,%xmm1
movsd  %xmm1,(%rdi,%rcx,8)
add    $0x2,%rcx
cmp    $0x14,%rcx
jne    12d0 <computePostCollisionDistributions+0x1d0>
ret

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

LLVM IR (-O2):
define void @computePostCollisionDistributions(double* nocapture %0, double* nocapture %1, double* nocapture %2) {
%4 = getelementptr double, double* %0, i64 19
%5 = getelementptr double, double* %2, i64 19
%6 = getelementptr double, double* %1, i64 1
%7 = icmp ugt double* %5, %0
%8 = icmp ugt double* %4, %2
%9 = and i1 %7, %8
%10 = icmp ugt double* %6, %0
%11 = icmp ugt double* %4, %1
%12 = and i1 %10, %11
%13 = or i1 %9, %12
br i1 %13, label %130, label %14
14: ; preds = %3
%15 = bitcast double* %0 to <2 x double>*
%16 = load <2 x double>, <2 x double>* %15
%17 = bitcast double* %2 to <2 x double>*
%18 = load <2 x double>, <2 x double>* %17
%19 = fsub <2 x double> %16, %18
%20 = load double, double* %1
%21 = insertelement <2 x double> poison, double %20, i64 0
%22 = shufflevector <2 x double> %21, <2 x double> poison, <2 x i32> zeroinitializer
%23 = fdiv <2 x double> %19, %22
%24 = fsub <2 x double> %16, %23
%25 = bitcast double* %0 to <2 x double>*
store <2 x double> %24, <2 x double>* %25
%26 = getelementptr inbounds double, double* %0, i64 2
%27 = bitcast double* %26 to <2 x double>*
%28 = load <2 x double>, <2 x double>* %27
%29 = getelementptr inbounds double, double* %2, i64 2
%30 = bitcast double* %29 to <2 x double>*
%31 = load <2 x double>, <2 x double>* %30
%32 = fsub <2 x double> %28, %31
%33 = load double, double* %1
%34 = insertelement <2 x double> poison, double %33, i64 0
%35 = shufflevector <2 x double> %34, <2 x double> poison, <2 x i32> zeroinitializer
%36 = fdiv <2 x double> %32, %35
%37 = fsub <2 x double> %28, %36
%38 = bitcast double* %26 to <2 x double>*
store <2 x double> %37, <2 x double>* %38
%39 = getelementptr inbounds double, double* %0, i64 4
%40 = bitcast double* %39 to <2 x double>*
%41 = load <2 x double>, <2 x double>* %40
%42 = getelementptr inbounds double, double* %2, i64 4
%43 = bitcast double* %42 to <2 x double>*
%44 = load <2 x double>, <2 x double>* %43
%45 = fsub <2 x double> %41, %44
%46 = load double, double* %1
%47 = insertelement <2 x double> poison, double %46, i64 0
%48 = shufflevector <2 x double> %47, <2 x double> poison, <2 x i32> zeroinitializer
%49 = fdiv <2 x double> %45, %48
%50 = fsub <2 x double> %41, %49
%51 = bitcast double* %39 to <2 x double>*
store <2 x double> %50, <2 x double>* %51
%52 = getelementptr inbounds double, double* %0, i64 6
%53 = bitcast double* %52 to <2 x double>*
%54 = load <2 x double>, <2 x double>* %53
%55 = getelementptr inbounds double, double* %2, i64 6
%56 = bitcast double* %55 to <2 x double>*
%57 = load <2 x double>, <2 x double>* %56
%58 = fsub <2 x double> %54, %57
%59 = load double, double* %1
%60 = insertelement <2 x double> poison, double %59, i64 0
%61 = shufflevector <2 x double> %60, <2 x double> poison, <2 x i32> zeroinitializer
%62 = fdiv <2 x double> %58, %61
%63 = fsub <2 x double> %54, %62
%64 = bitcast double* %52 to <2 x double>*
store <2 x double> %63, <2 x double>* %64
%65 = getelementptr inbounds double, double* %0, i64 8
%66 = bitcast double* %65 to <2 x double>*
%67 = load <2 x double>, <2 x double>* %66
%68 = getelementptr inbounds double, double* %2, i64 8
%69 = bitcast double* %68 to <2 x double>*
%70 = load <2 x double>, <2 x double>* %69
%71 = fsub <2 x double> %67, %70
%72 = load double, double* %1
%73 = insertelement <2 x double> poison, double %72, i64 0
%74 = shufflevector <2 x double> %73, <2 x double> poison, <2 x i32> zeroinitializer
%75 = fdiv <2 x double> %71, %74
%76 = fsub <2 x double> %67, %75
%77 = bitcast double* %65 to <2 x double>*
store <2 x double> %76, <2 x double>* %77
%78 = getelementptr inbounds double, double* %0, i64 10
%79 = bitcast double* %78 to <2 x double>*
%80 = load <2 x double>, <2 x double>* %79
%81 = getelementptr inbounds double, double* %2, i64 10
%82 = bitcast double* %81 to <2 x double>*
%83 = load <2 x double>, <2 x double>* %82
%84 = fsub <2 x double> %80, %83
%85 = load double, double* %1
%86 = insertelement <2 x double> poison, double %85, i64 0
%87 = shufflevector <2 x double> %86, <2 x double> poison, <2 x i32> zeroinitializer
%88 = fdiv <2 x double> %84, %87
%89 = fsub <2 x double> %80, %88
%90 = bitcast double* %78 to <2 x double>*
store <2 x double> %89, <2 x double>* %90
%91 = getelementptr inbounds double, double* %0, i64 12
%92 = bitcast double* %91 to <2 x double>*
%93 = load <2 x double>, <2 x double>* %92
%94 = getelementptr inbounds double, double* %2, i64 12
%95 = bitcast double* %94 to <2 x double>*
%96 = load <2 x double>, <2 x double>* %95
%97 = fsub <2 x double> %93, %96
%98 = load double, double* %1
%99 = insertelement <2 x double> poison, double %98, i64 0
%100 = shufflevector <2 x double> %99, <2 x double> poison, <2 x i32> zeroinitializer
%101 = fdiv <2 x double> %97, %100
%102 = fsub <2 x double> %93, %101
%103 = bitcast double* %91 to <2 x double>*
store <2 x double> %102, <2 x double>* %103
%104 = getelementptr inbounds double, double* %0, i64 14
%105 = bitcast double* %104 to <2 x double>*
%106 = load <2 x double>, <2 x double>* %105
%107 = getelementptr inbounds double, double* %2, i64 14
%108 = bitcast double* %107 to <2 x double>*
%109 = load <2 x double>, <2 x double>* %108
%110 = fsub <2 x double> %106, %109
%111 = load double, double* %1
%112 = insertelement <2 x double> poison, double %111, i64 0
%113 = shufflevector <2 x double> %112, <2 x double> poison, <2 x i32> zeroinitializer
%114 = fdiv <2 x double> %110, %113
%115 = fsub <2 x double> %106, %114
%116 = bitcast double* %104 to <2 x double>*
store <2 x double> %115, <2 x double>* %116
%117 = getelementptr inbounds double, double* %0, i64 16
%118 = bitcast double* %117 to <2 x double>*
%119 = load <2 x double>, <2 x double>* %118
%120 = getelementptr inbounds double, double* %2, i64 16
%121 = bitcast double* %120 to <2 x double>*
%122 = load <2 x double>, <2 x double>* %121
%123 = fsub <2 x double> %119, %122
%124 = load double, double* %1
%125 = insertelement <2 x double> poison, double %124, i64 0
%126 = shufflevector <2 x double> %125, <2 x double> poison, <2 x i32> zeroinitializer
%127 = fdiv <2 x double> %123, %126
%128 = fsub <2 x double> %119, %127
%129 = bitcast double* %117 to <2 x double>*
store <2 x double> %128, <2 x double>* %129
br label %130
130: ; preds = %14, %3
%131 = phi i64 [ 0, %3 ], [ 18, %14 ]
%132 = getelementptr inbounds double, double* %0, i64 %131
%133 = load double, double* %132
%134 = getelementptr inbounds double, double* %2, i64 %131
%135 = load double, double* %134
%136 = fsub double %133, %135
%137 = load double, double* %1
%138 = fdiv double %136, %137
%139 = fsub double %133, %138
store double %139, double* %132
%140 = or i64 %131, 1
br i1 %13, label %141, label %162
141: ; preds = %130, %141
%142 = phi i64 [ %160, %141 ], [ %140, %130 ]
%143 = getelementptr inbounds double, double* %0, i64 %142
%144 = load double, double* %143
%145 = getelementptr inbounds double, double* %2, i64 %142
%146 = load double, double* %145
%147 = fsub double %144, %146
%148 = load double, double* %1
%149 = fdiv double %147, %148
%150 = fsub double %144, %149
store double %150, double* %143
%151 = add nuw nsw i64 %142, 1
%152 = getelementptr inbounds double, double* %0, i64 %151
%153 = load double, double* %152
%154 = getelementptr inbounds double, double* %2, i64 %151
%155 = load double, double* %154
%156 = fsub double %153, %155
%157 = load double, double* %1
%158 = fdiv double %156, %157
%159 = fsub double %153, %158
store double %159, double* %152
%160 = add nuw nsw i64 %142, 2
%161 = icmp eq i64 %160, 19
br i1 %161, label %162, label %141
162: ; preds = %141, %130
ret void
}