Sum of integers optimization

[Ionut]

Hello All,
  I am playing with below example (very trivial, just computing a sum of 1...N integers):
@Benchmarkpublic long sum() {    long sum = 0;    for (int i = 1; i <= N; i++) {   sum += i; }    return sum;}

Generated asm on my machine (snapshot from the main scalar loop):                                ......................................................                            ↗  0x00007f4779bff060: movsxd r10,r11d                           │  0x00007f4779bff063: add    rax,r10
  7.67%   24.83% │  0x00007f4779bff066: add    rax,r10  6.11%    3.64%  │  0x00007f4779bff069: add    rax,r10  4.54%    3.71%  │  0x00007f4779bff06c: add    rax,r10  6.12%    5.85%  │  0x00007f4779bff06f: add    rax,r10  5.75%    4.21%  │  0x00007f4779bff072: add    rax,r10  5.96%    4.38%  │  0x00007f4779bff075: add    rax,r10  4.23%    3.63%  │  0x00007f4779bff078: add    rax,r10  6.70%    6.32%  │  0x00007f4779bff07b: add    rax,r10  7.40%    4.56%  │  0x00007f4779bff07e: add    rax,r10  4.61%    3.31%  │  0x00007f4779bff081: add    rax,r10  5.45%    5.24%  │  0x00007f4779bff084: add    rax,r10  5.99%    5.14%  │  0x00007f4779bff087: add    rax,r10  7.70%    5.36%  │  0x00007f4779bff08a: add    rax,r10  5.17%    4.16%  │  0x00007f4779bff08d: add    rax,r10  3.97%    3.83%  │  0x00007f4779bff090: add    rax,r10  4.80%    3.97%  │  0x00007f4779bff093: add    rax,0x78                                                                    5.92%    5.97%  │  0x00007f4779bff097: add    r11d,0x10              0.01%      │  0x00007f4779bff09b: cmp    r11d,0x5f5e0f2
                          ╰  0x00007f4779bff0a2: jl     0x00007f4779bff060                                 ......................................................

Questions: - Would it be possible for JIT C2 to perform a better optimization in this context, as for example replacing the main loop (which might be costly) by a reduction formula as N*(N-1)/2 (in this specific case)? - Is there any context where JIT C2 can perform such optimization but I am missing? - If not, what prevents it for doing this?
ThanksIonut

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