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SafeHeap: Prepare for emscripten_get_sbrk_ptr #2331

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Merged
kripken merged 2 commits into from
Sep 6, 2019
Merged

SafeHeap: Prepare for emscripten_get_sbrk_ptr #2331

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0ef8af2
wip
kripken Sep 5, 2019
7549c0b
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kripken Sep 5, 2019
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30 changes: 22 additions & 8 deletions src/passes/SafeHeap.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@
namespace wasm {

const Name DYNAMICTOP_PTR_IMPORT("DYNAMICTOP_PTR");
const Name GET_SBRK_PTR_IMPORT("emscripten_get_sbrk_ptr");
const Name SEGFAULT_IMPORT("segfault");
const Name ALIGNFAULT_IMPORT("alignfault");

Expand Down Expand Up @@ -111,19 +112,27 @@ struct SafeHeap : public Pass {
addGlobals(module, module->features);
}

Name dynamicTopPtr, segfault, alignfault;
Name dynamicTopPtr, getSbrkPtr, segfault, alignfault;

void addImports(Module* module) {
ImportInfo info(*module);
// Older emscripten imports env.DYNAMICTOP_PTR.
// Newer emscripten imports emscripten_get_sbrk_ptr(), which is later
// optimized to have the number in the binary.
if (auto* existing = info.getImportedGlobal(ENV, DYNAMICTOP_PTR_IMPORT)) {
dynamicTopPtr = existing->name;
} else if (auto* existing =
info.getImportedFunction(ENV, GET_SBRK_PTR_IMPORT)) {
getSbrkPtr = existing->name;
} else {
auto* import = new Global;
import->name = dynamicTopPtr = DYNAMICTOP_PTR_IMPORT;
auto* import = new Function;
import->name = getSbrkPtr = GET_SBRK_PTR_IMPORT;
import->module = ENV;
import->base = DYNAMICTOP_PTR_IMPORT;
import->type = i32;
module->addGlobal(import);
import->base = GET_SBRK_PTR_IMPORT;
auto* functionType = ensureFunctionType("i", module);
import->type = functionType->name;
FunctionTypeUtils::fillFunction(import, functionType);
module->addFunction(import);
}
if (auto* existing = info.getImportedFunction(ENV, SEGFAULT_IMPORT)) {
segfault = existing->name;
Expand Down Expand Up @@ -315,6 +324,12 @@ struct SafeHeap : public Pass {
makeBoundsCheck(Type type, Builder& builder, Index local, Index bytes) {
auto upperOp = options.lowMemoryUnused ? LtUInt32 : EqInt32;
auto upperBound = options.lowMemoryUnused ? PassOptions::LowMemoryBound : 0;
Expression* sbrkPtr;
if (dynamicTopPtr.is()) {
sbrkPtr = builder.makeGlobalGet(dynamicTopPtr, i32);
} else {
sbrkPtr = builder.makeCall(getSbrkPtr, {}, i32);
}
return builder.makeIf(
builder.makeBinary(
OrInt32,
Expand All @@ -326,8 +341,7 @@ struct SafeHeap : public Pass {
builder.makeBinary(AddInt32,
builder.makeLocalGet(local, i32),
builder.makeConst(Literal(int32_t(bytes)))),
builder.makeLoad(
4, false, 0, 4, builder.makeGlobalGet(dynamicTopPtr, i32), i32))),
builder.makeLoad(4, false, 0, 4, sbrkPtr, i32))),
builder.makeCall(segfault, {}, none));
}
};
Expand Down
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