LLDB can use the wasm name section to populate its symbol table and get
names for functions. However the index space used in the name section is
the "function index space" which includes imported as well as locally
defined functions.
My original implementation for parsing Wasm segments was wrong in two
related ways. I had a bug in calculating the file vm address and I
didn't fully understand the difference between active and passive
segments and how that impacted their file vm address.
With this PR, we now support parsing init expressions for active
segments, rather than just skipping over them. This is necessary to
determine where they get loaded.
Similar to llvm-objdump, we currently only support simple opcodes (i.e.
constants). We also currently do not support active segments that use a
non-zero memory index. However this covers all segments for a
non-trivial Swift binary compiled to Wasm.
This is a continuation of #153494. In a WebAssembly file, the "name"
section contains names for the segments in the data section
(WASM_NAMES_DATA_SEGMENT). We already parse these as symbols, and with
this PR, we now also create sub-sections for each of the segments.
This PR adds support for parsing the data symbols from the WebAssembly
name section, which consists of a name and address range for the
segments in the Wasm data section. Unlike other object file formats,
Wasm has no symbols for referencing items within those segments (i.e.
symbols the user has defined).
This PR adds support for parsing the WebAssembly symbol table. The
symbol table is encoded in the "names" section and contains names and
indexes into other sections. For now we only support parsing function
(code) symbols. The result is that you can set breakpoints by symbol
name, while previously breakpoints by name required debug info (DWARF).
This is also necessary for Swift, which checks for the presence of
`swift_release` as a heuristic to determine if there's a static Swift
stdlib.
It may be useful to search symbol table entries by mangled instead
of demangled names. Add this optional functionality in the SymbolTable
functions.
Differential Revision: https://reviews.llvm.org/D130803
