[Debug][AArch64] Do not crash on unknown subreg register sizes. (#160442)
The AArch64 zsub regs are scalable, so defined with a size of -1 (which
comes through as 65535). The RegisterSize is only 128, so code to try
and find overlapping regs of a z30_z31 in DwarfEmitter can crash on
trying to access out of range bits in a BitVector. Hexagon and x86 also
contain subregs with unknown sizes.
Ideally most of these would be scalable values but in the meantime add a
check that the register are small enough to overlap with the current
register size, to prevent us from crashing.
This fixes the issue reported on #153810.
llvm-project
88a2f405 - [Debug][AArch64] Do not crash on unknown subreg register sizes. (#160442)
