Re: [PATCH] Fix math transformation on targets without c99 math functions

["Andre Vieira (lists)" <Andre dot SimoesDiasVieira at arm dot com>]

On 11/01/16 16:39, Jakub Jelinek wrote:
> On Mon, Jan 11, 2016 at 05:11:21PM +0100, Christophe Lyon wrote:
> > I tested a similar version on my side. It just makes the test become
> > UNSUPPORTED for arm/aarch64 + newlib. They used to pass, though.
>
> Is anything bad on that?  The test tests functions that newlib does not
> implement, so it is not wrong not to optimize those.
>
> 	Jakub

Unfortunately c99_functions is a very wide net. For instance, newlib 
supports the ceill, but doesn't support wscanf_s nor any bounds checking 
function I think.

I extracted all function names from the C99 standard and did a quick nm 
and grep to look into whether newlib defined these for arm-none-eabi.

The functions I found missing fall into the following sections:
- Complex Arithmetic (which fall under the function_c99_math_complex class)
- floating-point environment
- Functions for greatest-width integer types
- atomics (missing atomic_is_lock_free and atomic_fetch_key)
- Bounds-checking interfaces

So arm-none-eabi used to be able to "legally" perform the transformation 
that we are speaking of. Though since that optimization is now guarded 
with the function_c99_misc class it is no longer performed, since we can 
not claim newlib supports all functions that are caught by 
function_c99_misc.

I don't quite know how to proceed. I suspect a new function class for 
C99 math functions (excluding complex) would help here and probably more 
places too. Though, I don't know how much work it would be to split 
function_c99_misc in that manner.

Opinions welcome!!

Cheers,
Andre