[all-commits] [llvm/llvm-project] a62119: [libc] Move printf long double to simple calc (#75...

[michaelrj-google via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a621198a035cdc700f08507879db902f22f8a5e2
      https://github.com/llvm/llvm-project/commit/a621198a035cdc700f08507879db902f22f8a5e2
  Author: michaelrj-google <71531609+michaelrj-google at users.noreply.github.com>
  Date:   2024-01-25 (Thu, 25 Jan 2024)

  Changed paths:
    M libc/config/config.json
    M libc/docs/dev/printf_behavior.rst
    M libc/src/__support/UInt.h
    M libc/src/__support/float_to_string.h
    M libc/test/src/stdio/sprintf_test.cpp
    M utils/bazel/llvm-project-overlay/libc/BUILD.bazel

  Log Message:
  -----------
  [libc] Move printf long double to simple calc (#75414)

The Ryu algorithm is very fast with its table, but that table grows too
large for long doubles. This patch adds a method of calculating the
digits of long doubles using just wide integers and fast modulo
operations. This results in significant performance improvements vs the
previous int calc mode, while taking up a similar amound of peak memory.
It will be slow in some %e/%g cases, but reasonable fast for %f with no
loss of accuracy.