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Limit the number of passive segments to work around a Chrome bug #2613

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Merged
merged 2 commits into from
Jan 23, 2020
Merged

Limit the number of passive segments to work around a Chrome bug #2613

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Limit the number of passive segments to work around a Chrome bug
tlively Jan 22, 2020
81b8aeb
Update comment, name, code
tlively Jan 22, 2020
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10 changes: 9 additions & 1 deletion src/passes/MemoryPacking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,11 @@ Expression* makeShiftedMemorySize(Builder& builder) {
struct MemoryPacking : public Pass {
size_t dropStateGlobalCount = 0;

// FIXME: Chrome has a bug decoding section indices that prevents it from
// using more than 63. Just use WebLimitations::MaxDataSegments once this is
// fixed. See https://bugs.chromium.org/p/v8/issues/detail?id=10151.
uint32_t maxSegments;

void run(PassRunner* runner, Module* module) override;
void optimizeBulkMemoryOps(PassRunner* runner, Module* module);
void getSegmentReferrers(Module* module, std::vector<Referrers>& referrers);
Expand Down Expand Up @@ -116,6 +121,9 @@ void MemoryPacking::run(PassRunner* runner, Module* module) {
return;
}

maxSegments = module->features.hasBulkMemory()
? 63
: uint32_t(WebLimitations::MaxDataSegments);
auto& segments = module->memory.segments;

// For each segment, a list of bulk memory instructions that refer to it
Expand Down Expand Up @@ -436,7 +444,7 @@ void MemoryPacking::createSplitSegments(Builder& builder,
offset = segment.offset;
}
}
if (WebLimitations::MaxDataSegments <= packed.size() + segmentsRemaining) {
if (maxSegments <= packed.size() + segmentsRemaining) {
// Give up splitting and merge all remaining ranges except end zeroes
auto lastNonzero = ranges.end() - 1;
if (lastNonzero->isZero) {
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2 changes: 1 addition & 1 deletion src/wasm-binary.h
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Expand Up @@ -47,7 +47,7 @@ enum {

// wasm VMs on the web have decided to impose some limits on what they
// accept
enum WebLimitations {
enum WebLimitations : uint32_t {
MaxDataSegments = 100 * 1000,
MaxFunctionBodySize = 128 * 1024,
MaxFunctionLocals = 50 * 1000
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