On Sat, 21 May 2022 10:31:25 GMT, Quan Anh Mai <d...@openjdk.java.net> wrote:
>> Hi, >> >> This patch optimises the matching rules for floating-point comparison with >> respects to eq/ne on x86-64 >> >> 1, When the inputs of a comparison is the same (i.e `isNaN` patterns), `ZF` >> is always set, so we don't need `cmpOpUCF2` for the eq/ne cases, which >> improves the sequence of `If (CmpF x x) (Bool ne)` from >> >> ucomiss xmm0, xmm0 >> jp label >> jne label >> >> into >> >> ucomiss xmm0, xmm0 >> jp label >> >> 2, The move rules for `cmpOpUCF2` is missing, which makes patterns such as >> `x == y ? 1 : 0` to fall back to `cmpOpU`, which have a really high cost of >> fixing the flags, such as >> >> xorl ecx, ecx >> ucomiss xmm0, xmm1 >> jnp done >> pushf >> andq [rsp], 0xffffff2b >> popf >> done: >> movl eax, 1 >> cmovel eax, ecx >> >> The patch changes this sequence into >> >> xorl ecx, ecx >> ucomiss xmm0, xmm1 >> movl eax, 1 >> cmovpl eax, ecx >> cmovnel eax, ecx >> >> 3, The patch also changes the pattern of `isInfinite` to be more optimised >> by using `Math.abs` to reduce 1 comparison and compares the result with >> `MAX_VALUE` since `>` is more optimised than `==` for floating-point types. >> >> The benchmark results are as follow: >> >> Before >> After >> Benchmark Mode Cnt Score Error Score >> Error Unit Ratio >> FPComparison.equalDouble avgt 5 2876.242 ± 58.875 594.636 ± >> 8.922 ns/op 4.84 >> FPComparison.equalFloat avgt 5 3062.430 ± 31.371 663.849 ± >> 3.656 ns/op 4.61 >> FPComparison.isFiniteDouble avgt 5 475.749 ± 19.027 518.309 ± >> 107.352 ns/op 0.92 >> FPComparison.isFiniteFloat avgt 5 506.525 ± 14.417 515.576 ± >> 14.669 ns/op 0.98 >> FPComparison.isInfiniteDouble avgt 5 1232.800 ± 31.677 621.185 ± >> 11.935 ns/op 1.98 >> FPComparison.isInfiniteFloat avgt 5 1234.708 ± 70.239 623.566 ± >> 15.206 ns/op 1.98 >> FPComparison.isNanDouble avgt 5 2255.847 ± 7.238 400.124 ± >> 0.762 ns/op 5.64 >> FPComparison.isNanFloat avgt 5 2567.044 ± 36.078 546.486 ± >> 1.509 ns/op 4.70 >> >> Thank you very much. > > Quan Anh Mai has updated the pull request incrementally with one additional > commit since the last revision: > > comments Thank you very much for your reviews and testing. ------------- PR: https://git.openjdk.java.net/jdk/pull/8525
