[Dwarf-discuss] ISSUE: CPU vector types.

David Blaikie dblaikie@gmail.com
Tue Mar 28 20:17:29 GMT 2023

> DW_AT[_GNU]_vector is best understood not as "a hardware vector register" but rather as a marker that "this type is eligible to be passed in hardware vector registers at function boundaries according to the platform ABI".

My 2c would not be to describe these in terms of
hardware/implementations (that gets confusing/blurs the line between
variable/types and locations - as you say, these things can be stored
in memory, so they aren't uniquely in registers - you might have a
member of this type in a struct passed in memory and need to know the
ABI/struct layout for that, etc), but at the source level - which the
ABI is defined in those same terms. Overloading, for instance, still
applies if these are different types - so other debugger features need
to work based on this type information.

So it seems like a simpler question is:

How should DWARF producers/consumers expect to encode the source
example Ben provided (well, simplified a bit):

#include <x86intrin.h>

void f( __m128 a){

What DWARF should be used to describe the type of 'a'? And how does
this encoding scale to all the other similar intrinsic types?

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