[all-commits] [llvm/llvm-project] 30dae3: Fix LLP64 detection in SwapByteOrder.h

[Reid Kleckner via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 30dae38349cbe293bee0705b313dc747e53afd49
      https://github.com/llvm/llvm-project/commit/30dae38349cbe293bee0705b313dc747e53afd49
  Author: Reid Kleckner <rnk at google.com>
  Date:   2020-02-26 (Wed, 26 Feb 2020)

  Changed paths:
    M llvm/include/llvm/Support/SwapByteOrder.h

  Log Message:
  -----------
  Fix LLP64 detection in SwapByteOrder.h

MSVC does not define __LONG_MAX__, so we were just getting lucky in this
conditional:
  #if __LONG_MAX__ == __INT_MAX__

Undefined identifiers evaluate to zero in preprocessor conditionals, so
this became true, which happens to work for MSVC platforms.

Instead, use this pattern and let the compiler constant fold:
  return sizeof(long) == sizeof(int) ? SwapByteOrder_32((uint32_t)C)
                                     : SwapByteOrder_64((uint64_t)C);