[PATCH] middle-end: Skip initialization of opaque type register variables [PR103127]

[Peter Bergner]

On 11/30/21 2:44 PM, Qing Zhao via Gcc-patches wrote:
> Sorry for the confusing…
> My major question is:  
> 
> for a variable of type __vector_pair,  could it be in a register?

Yes.  To be pedantic, it will live in a vector register pair.


> If it could be in a register, can we initialize this register with some constant value? 

For a __vector_pair, no, not as it is setup now.  We also do not have a
use case where we would want to initialize a __vector_pair to a constant.
Our normal (only?) use case with a __vector_pair is to load it up with
some actual data from memory that represents a (partial) row of a matrix. 

For __vector_quad, it too lives in a register (accumulator register) and
represents a small matrix.  We have the __builtin_mma_xxsetaccz (&acc)
builtin to initialize it to a zero constant.

Peter