[Bug target/102783] [powerpc] FPSCR manipulations cannot be relied upon

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102783

--- Comment #6 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
Generically (and if the command-line options are such that floating-point 
control / status bits are to be respected by optimizations), *any* 
function call might access or modify floating-point control and status 
bits, subject to e.g. const functions not being able to access them, pure 
functions not being able to modify them, functions whose body is known 
having properties based on analysis of that body, built-in functions 
having semantics based on what the compiler knows about those functions.  
And then a subset of asms may similarly access or modify them (based on 
inputs / outputs / clobbers, but maybe on some architectures existing 
practice doesn't provide a register name that inputs / outputs / clobbers 
can use to refer to floating-point state).

Then you'd need something like Marc Glisse's -ffenv-access patches (August 
2020) to represent the other side of things, how floating-point operations 
also access / modify such bits.