stillwater-sc / universal / 24864610179

84%

master: 84%

Build Type

push

github

Committed by web-flow

Commit Message

feat(blockbinary): promote arithmetic operators to constexpr (PR 2 of #713) (#716)

* feat(blockbinary): promote arithmetic operators to constexpr (PR 2 of #713)

Mark blockbinary's arithmetic and bitwise operators constexpr so that posit
convert_<>() and the broader Universal codebase can do constexpr blockbinary
arithmetic. This is the prerequisite for Phase 2 of issue #713 (constexpr
IEEE-754 -> posit conversion) and is independently valuable for any future
code that needs compile-time blockbinary arithmetic.

Operators promoted to constexpr:
  blockbinary::operator+= operator-= operator++ operator-- operator<<=
  operator>>= operator|= operator&= operator^=
  free truncate(...)  free twosComplement(...)
  posit_impl::convert_<>()

Implementation notes:
- The bitsInBlock==64 path of operator+= calls addcarry(), which uses
  platform-specific intrinsics that are not constexpr on MSVC. Dispatch
  via std::is_constant_evaluated() to a portable carry-detection path
  in constexpr context, while keeping the intrinsic for runtime perf.
- The general multi-block path used pointer-arithmetic loops. Rewritten
  as index-based loops, which are constexpr-friendly.
- The two `if (_trace_conversion)` runtime branches in convert_<>() that
  called std::cout were converted to `if constexpr (_trace_conversion)`
  to satisfy the constant-expression requirement.

The following blockbinary operators are intentionally left non-constexpr in
this PR (out of scope; they have separate intrinsic dependencies):
  operator*= (uses mul128), operator/=, operator%=

Tests:
- internal/blockbinary/api/constexpr.cpp expanded with static_assert smoke
  tests covering operator+=, ++, <<=, |=, twosComplement across uint8/uint64
  limbs, single-block and multi-block configurations.
- Verified constexpr posit_impl::convert_<>() compiles and produces bit-
  identical encoding to runtime invocation.

Cross-type regression validation (gcc-13 + clang-18, both -std=c++20):
  blockbinary: bb... (continued)

Coverage Stats

28 of 38 new or added lines in 3 files covered. (73.68%)

6 existing lines in 1 file now uncovered.

44907 of 53228 relevant lines covered (84.37%)

6505383.69 hits per line