[libcxx-commits] [PATCH] D59178: [libc++] Speedup to_string and to_wstring for integers using stack buffer and SSO

[Vlad Tsyrklevich via Phabricator via libcxx-commits]

vlad.tsyrklevich added a comment.

I tested the following change and verified that it works for the numeric example above, but don't have time to write a test and monitor for build failures so I'm going to revert this change for now. Leaving it here for whoever wants to pick it up:

  --- a/libcxx/src/charconv.cpp
  +++ b/libcxx/src/charconv.cpp
  @@ -176,22 +176,39 @@ __u64toa(uint64_t value, char* buffer)
           const uint32_t b0 = v0 / 10000;
           const uint32_t c0 = v0 % 10000;
  
  -        if (v0 < 1000000)
  +        if (b0)
           {
  -            if (v0 < 100000)
  -                buffer = append1(buffer, b0);
  +            if (b0 < 100)
  +            {
  +                if (b0 < 10)
  +                    buffer = append1(buffer, b0);
  +                else
  +                    buffer = append2(buffer, b0);
  +            }
  +            else
  +            {
  +                if (b0 < 1000)
  +                    buffer = append3(buffer, b0);
  +                else
  +                    buffer = append4(buffer, b0);
  +            }
  +        }
  +
  +        if (c0 < 100)
  +        {
  +            if (c0 < 10)
  +                buffer = append1(buffer, c0);
               else
  -                buffer = append2(buffer, b0);
  +                buffer = append2(buffer, c0);
           }
           else
           {
  -            if (v0 < 10000000)
  -                buffer = append3(buffer, b0);
  +            if (c0 < 1000)
  +                buffer = append3(buffer, c0);
               else
  -                buffer = append4(buffer, b0);
  +                buffer = append4(buffer, c0);
           }
  
  -        buffer = append4(buffer, c0);
           buffer = append4(buffer, v1 / 10000);
           buffer = append4(buffer, v1 % 10000);
       }


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D59178/new/

https://reviews.llvm.org/D59178