[PATCH] Add RTX codes for BITREVERSE and COPYSIGN.

[Joseph Myers]

On Sat, 6 May 2023, Roger Sayle wrote:

> An analysis of backend UNSPECs reveals that two of the most common UNSPECs
> across target backends are for copysign and bit reversal.  This patch
> adds RTX codes for these expressions to allow their representation to
> be standardized, and them to optimized by the middle-end RTL optimizers.

Note we have bug 50481 requesting (target-independent) built-in functions 
for bit reversal (so this patch could be useful as a basis for 
implementing such built-in functions, with appropriate lowering or libgcc 
implementation for targets without relevant instructions).

-- 
Joseph S. Myers
joseph@codesourcery.com