area-CodeGen-coreclrhelp wantedoptimization
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説明
I noticed that it's quite popular to use constants with Math.Pow, e.g.
double z = Math.Pow(x, 2);
// can be optimized to just
double z = x * x;
Codegen:
C.Test1(Double)
L0000: vzeroupper
L0003: vmovsd xmm1, qword [rip+0x15]
L000b: mov rax, 0x7ffec7f7cca0
L0015: jmp rax
C.Test2(Double)
L0000: vzeroupper
L0003: vmulsd xmm0, xmm0, xmm0
L0007: ret
E.g. Burgers benchmark uses it a lot https://github.com/dotnet/performance/blob/master/src/benchmarks/micro/coreclr/Burgers/Burgers.cs#L22
I am currently converting Math methods in Mono to LLVM intrinsic and noticed LLVM's InstCombine actually does it, see https://github.com/mono/mono/pull/16561
category:cq theme:floating-point skill-level:intermediate cost:medium