[SPIR-V] Fix generation of invalid SPIR-V in cases of of bitcasts between pointers and multiple null pointers used in the input LLVM IR (#118298)

This PR resolved the following issues:
(1) There are rare but possible cases when there are bitcasts between
pointers intertwined in a sophisticated way with loads, stores, function
calls and other instructions that are part of type deduction. In this
case we must account for inserted bitcasts between pointers rather than
just ignore them.
(2) Null pointers have the same constant representation but different
types. Type info from Intrinsic::spv_track_constant() refers to the
opaque (untyped) pointer, so that each MF/v-reg pair would fall into the
same Const record in Duplicate Tracker and would be represented by a
single OpConstantNull instruction, unless we use precise pointee type
info. We must be able to distinguish one constant (null) pointer from
another to avoid generating invalid code with inconsistent types of
operands.

0 files changed, 0 insertions, 0 deletions