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Flesh out emscripten metadata #8519

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merged 3 commits into from
May 2, 2019
Merged

Flesh out emscripten metadata #8519

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2870897
Flesh out emscripten metadata
rianhunter Apr 30, 2019
7e71f43
Make regex more strict
rianhunter May 1, 2019
eb14873
Address feedback
rianhunter May 1, 2019
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24 changes: 19 additions & 5 deletions tools/shared.py
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Original file line number Diff line number Diff line change
Expand Up @@ -518,7 +518,7 @@ def get_emscripten_version(path):
# For the Emscripten-specific WASM metadata section, follows semver, changes
# whenever metadata section changes structure
# NB: major version 0 implies no compatibility
(EMSCRIPTEN_METADATA_MAJOR, EMSCRIPTEN_METADATA_MINOR) = (0, 0)
(EMSCRIPTEN_METADATA_MAJOR, EMSCRIPTEN_METADATA_MINOR) = (0, 1)
# For the JS/WASM ABI, specifies the minimum ABI version required of
# the WASM runtime implementation by the generated WASM binary. It follows
# semver and changes whenever C types change size/signedness or
Expand Down Expand Up @@ -2979,8 +2979,20 @@ def delebify(buf, offset):

@staticmethod
def add_emscripten_metadata(js_file, wasm_file):
mem_size = Settings.STATIC_BUMP
WASM_PAGE_SIZE = 65536
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so STATIC_BUMP is no longer needed?

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STATIC_BUMP was being used to compute DYNAMICTOP_PTR and tempDoublePtr but since those are now not derived from STATIC_BUMP it's no longer necessary to store that.


mem_size = Settings.TOTAL_MEMORY // WASM_PAGE_SIZE
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@sbc100 sbc100 Apr 30, 2019 •
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Doesn't // do the wrong thing here and round down? I guess TOTAL_MEMORY is already guaranteed to be a multiple so probably fine.

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Yeah, the intent is to make sure mem_size is an integer. I could have done int(TOTAL_MEMORY / WASM_PAGE_SIZE) but this seemed better.

table_size = Settings.WASM_TABLE_SIZE
global_base = Settings.GLOBAL_BASE

js = open(js_file).read()
m = re.search(r"(^|\s)tempDoublePtr\s+=\s+(\d+)", js)
tempdouble_ptr = int(m.group(2))
m = re.search(r"(^|\s)DYNAMIC_BASE\s+=\s+(\d+)", js)
dynamic_base = int(m.group(2))
m = re.search(r"(^|\s)DYNAMICTOP_PTR\s+=\s+(\d+)", js)
dynamictop_ptr = int(m.group(2))

logger.debug('creating wasm emscripten metadata section with mem size %d, table size %d' % (mem_size, table_size,))
name = b'\x13emscripten_metadata' # section name, including prefixed size
contents = (
Expand All @@ -2994,11 +3006,13 @@ def add_emscripten_metadata(js_file, wasm_file):
WebAssembly.lebify(EMSCRIPTEN_ABI_MAJOR) +
WebAssembly.lebify(EMSCRIPTEN_ABI_MINOR) +

# static bump
WebAssembly.lebify(mem_size) +
WebAssembly.lebify(table_size) +
WebAssembly.lebify(global_base) +
WebAssembly.lebify(dynamic_base) +
WebAssembly.lebify(dynamictop_ptr) +
WebAssembly.lebify(tempdouble_ptr)

# table size
WebAssembly.lebify(table_size)
# NB: more data can be appended here as long as you increase
# the EMSCRIPTEN_METADATA_MINOR
)
Expand Down