Fix disassembler silent truncation - #14136
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`CompiledCodeBase::disassemble` hands each block to capstone's
`disasm_all`, which stops at the first instruction it cannot decode and
returns the instructions decoded so far rather than an error. Nothing
compared the bytes consumed against the length of the block, so that
instruction and everything after it simply disappeared from the listing.
This matters most for `precise-output` filetests: the truncated output is
blessed into the expectation, and the test then passes while asserting
nothing at all about those bytes. An encoding bug in an instruction that
capstone does not understand would be invisible.
It is easy to hit today. The bundled capstone cannot decode AVX-VNNI, so a
function containing `vpdpbusd` lost five instructions, the entire epilogue
included, leaving only:
; block1: ; offset 0x4
; movdqa %xmm0, %xmm5
; movdqa %xmm2, %xmm0
Print the remaining bytes as `.byte` directives, carrying over relocation
and trap annotations so those are not dropped either. This is the form
capstone itself emits for undecodable s390x instructions, where the
instruction length is encoded in the first two bits and it can therefore
resynchronize. x86 instruction length cannot be determined without
decoding, so there is no way to resynchronize and the whole tail of the
block is covered by the dump.
The updated expectations are purely additive; no existing disassembly line
changes. Those blocks end in constant pool data, which capstone already
rendered as meaningless instructions such as `addb %al, (%rax)` before
giving up partway through.
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