Every BDA dword read site still emitted in the entry function the add
of its first dword address with the overflow fault, a probe_bda_pointer
call, the wide loads, and one read_bda_dword_bytes call per extracted
dword. NVIDIA's pipeline compile time grows with every call left in the
entry function, so large compute programs with a few hundred such reads
spend 47-77 s in vkCreateComputePipelines.
A read site is now one call to a DontInline read_bda_span function, in
a stop and a coherent variant, taking the address, the immediate offset,
the mask of extracted dwords and the pc, which does the same steps in
the same order. Fault reasons, addresses, pcs, Volatile, the stop
behaviour and the APS5_BDA_BYTE_READS path are unchanged.
A BDA dword read whose span the probe rejects falls back to four byte
lookups with a branch each, and every fault was recorded inline with a
compare-exchange and seven stores. Both were copied into every read
site and both wave64 lane halves, so one large compute program grows
to about a million SPIR-V words and spends about 95 s in
vkCreateComputePipelines.
Faults are now recorded by one DontInline function, record_bda_fault,
and the byte fallback of a dword is read_bda_dword_bytes, in a stop
and a coherent variant, returning the value and whether the invocation
stops. Read order, fault reasons, pcs, Volatile and the stop behaviour
are unchanged, and so is the probe path.
Celegans12
boykopovar