Constant folding and loop unrolling

dump.rb

n = ARGV[0].to_i
s = (1..n).to_a.map { |i| i.to_s }.join(",")
s = "{" + s + "}"

puts <<"EOS"
#include <cstdio>
const int N = #{n};
const int a[] = #{s};

int func(int b[N]) { 
  int sum = 0;
  for (int i = 0; i < N; i++) { 
    sum += a[i] * b[i];
  } 
  return sum;
}

int main() { 
  int b[] = #{s};
  printf("%d\\n", func(b));
}
EOS

$ ruby dump.rb 10 > test.cpp  
$ clang++ -O3 test.cpp -S

_main:                                  ## @main
        .cfi_startproc
## %bb.0:
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset %rbp, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register %rbp
        leaq    L_.str(%rip), %rdi
        movl    $385, %esi              ## imm = 0x181
        xorl    %eax, %eax
        callq   _printf
        xorl    %eax, %eax
        popq    %rbp
        retq