Increment and decrement are equivalent to adding or subtracting 1. For
the floating-point values these operations depend on the current
rounding mode. Teach constant evaluator to perform ++ and -- according
to the current floating-point environment.
Pull request: https://github.com/llvm/llvm-project/pull/73770
This addresses a regression where pretty much all C++ compilations using
-frounding-math now fail, due to rounding being performed in constexpr
function definitions in the standard library.
This follows the "manifestly constant evaluated" approach described in
https://reviews.llvm.org/D87528#2270676 -- evaluations that are required
to succeed at compile time are permitted even in regions with dynamic
rounding modes, as are (unfortunately) the evaluation of the
initializers of local variables of const integral types.
Differential Revision: https://reviews.llvm.org/D89360
