On Sun, Sep 05, 2021 at 11:28:30PM +0100, Roger Sayle wrote: > This patch simplifies the RTX (subreg:HI (truncate:QI (reg:SI))) as > (truncate:HI (reg:SI)), and closely related variants.
Subregs of other than regs are undefined in RTL. You will first have to define this (in documentation as well as in other code that handles subregs). I doubt this is possible to do, subreg have so many overloaded meanings already. Segher
