Re: [PATCH] amdgcn: Add support for additional natively supported floating-point operations

[Andrew Stubbs <ams@codesourcery.com>]

On 08/09/2022 21:38, Kwok Cheung Yeung wrote:
> Hello
> 
> This patch adds support for some additional floating-point operations, 
> in scalar and vector modes, which are natively supported by the AMD GCN 
> instruction set, but haven't been implemented in GCC yet. With the 
> exception of frexp, these implement standard RTL names, and should be 
> utilised automatically by GCC.
> 
> The instructions for the transcendental functions are documented to have 
> limited numerical precision, so they are only used if 
> unsafe_math_optimizations are enabled for now.
> 
> The sin and cos instructions for some reason are scaled by 2*PI radians 
> (i.e. 1.0 == 2*PI radians/360 degrees), so their inputs need to be 
> scaled by 1/(2*PI) first. I've implemented this as an expander to two 
> instructions - one to do the pre-scaling, one to do the sin/cos. 
> 1/(2*PI) is a builtin constant for GCN, but the syntax to use it in the 
> LLVM assembler was wrong - now fixed.
> 
> I have also added some extra GCN-specific builtins to access the vector 
> versions of some of these operations (to implement vectorized versions 
> of library math routines) and to access the frexp operations.
> 
> Okay for trunk?

LGTM. I'm assuming you've checked the maths. :)

Andrew