Implement multibyte array store instructions

Add support for multibyte array store instructions as proposed in the
WebAssembly multibyte proposal. These instructions allow storing values
of various byte widths directly into i8 arrays, avoiding the need for
manual bit manipulation and masking.

Link: https://github.com/WebAssembly/multibyte

Author: brendandahl

scripts/clusterfuzz/run.py

@@ -94,6 +94,7 @@
     '--disable-strings',
     '--disable-stack-switching',
     '--disable-relaxed-atomics',
+    '--disable-multibyte',
 ]
 
 

src/binaryen-c.cpp

@@ -502,6 +502,9 @@ BinaryenFeatures BinaryenFeatureCallIndirectOverlong(void) {
 BinaryenFeatures BinaryenFeatureRelaxedAtomics(void) {
   return static_cast<BinaryenFeatures>(FeatureSet::RelaxedAtomics);
 }
+BinaryenFeatures BinaryenFeatureMultibyte(void) {
+  return static_cast<BinaryenFeatures>(FeatureSet::Multibyte);
+}
 BinaryenFeatures BinaryenFeatureAll(void) {
   return static_cast<BinaryenFeatures>(FeatureSet::All);
 }

src/binaryen-c.h

@@ -244,6 +244,7 @@ BINARYEN_API BinaryenFeatures BinaryenFeatureFP16(void);
 BINARYEN_API BinaryenFeatures BinaryenFeatureBulkMemoryOpt(void);
 BINARYEN_API BinaryenFeatures BinaryenFeatureCallIndirectOverlong(void);
 BINARYEN_API BinaryenFeatures BinaryenFeatureRelaxedAtomics(void);
+BINARYEN_API BinaryenFeatures BinaryenFeatureMultibyte(void);
 BINARYEN_API BinaryenFeatures BinaryenFeatureAll(void);
 
 // Modules

src/interpreter/interpreter.cpp

@@ -262,6 +262,7 @@ struct ExpressionInterpreter : OverriddenVisitor<ExpressionInterpreter, Flow> {
   Flow visitArrayNewFixed(ArrayNewFixed* curr) { WASM_UNREACHABLE("TODO"); }
   Flow visitArrayGet(ArrayGet* curr) { WASM_UNREACHABLE("TODO"); }
   Flow visitArraySet(ArraySet* curr) { WASM_UNREACHABLE("TODO"); }
+  Flow visitArrayStore(ArrayStore* curr) { WASM_UNREACHABLE("TODO"); }
   Flow visitArrayLen(ArrayLen* curr) { WASM_UNREACHABLE("TODO"); }
   Flow visitArrayCopy(ArrayCopy* curr) { WASM_UNREACHABLE("TODO"); }
   Flow visitArrayFill(ArrayFill* curr) { WASM_UNREACHABLE("TODO"); }

src/ir/ReFinalize.cpp

@@ -171,6 +171,7 @@ void ReFinalize::visitArrayNewElem(ArrayNewElem* curr) { curr->finalize(); }
 void ReFinalize::visitArrayNewFixed(ArrayNewFixed* curr) { curr->finalize(); }
 void ReFinalize::visitArrayGet(ArrayGet* curr) { curr->finalize(); }
 void ReFinalize::visitArraySet(ArraySet* curr) { curr->finalize(); }
+void ReFinalize::visitArrayStore(ArrayStore* curr) { curr->finalize(); }
 void ReFinalize::visitArrayLen(ArrayLen* curr) { curr->finalize(); }
 void ReFinalize::visitArrayCopy(ArrayCopy* curr) { curr->finalize(); }
 void ReFinalize::visitArrayFill(ArrayFill* curr) { curr->finalize(); }

src/ir/child-typer.h

@@ -1096,6 +1096,20 @@ template<typename Subtype> struct ChildTyper : OverriddenVisitor<Subtype> {
     note(&curr->value, type);
   }
 
+  void visitArrayStore(ArrayStore* curr,
+                       std::optional<HeapType> ht = std::nullopt) {
+    if (!ht) {
+      if (!curr->ref->type.isRef()) {
+        self().noteUnknown();
+        return;
+      }
+      ht = curr->ref->type.getHeapType();
+    }
+    note(&curr->ref, Type(*ht, Nullable));
+    note(&curr->index, Type::i32);
+    note(&curr->value, curr->valueType);
+  }
+
   void visitArrayLen(ArrayLen* curr) {
     note(&curr->ref, Type(HeapType::array, Nullable));
   }

src/ir/cost.h

@@ -753,6 +753,10 @@ struct CostAnalyzer : public OverriddenVisitor<CostAnalyzer, CostType> {
     return 2 + nullCheckCost(curr->ref) + visit(curr->ref) +
            visit(curr->index) + visit(curr->value);
   }
+  CostType visitArrayStore(ArrayStore* curr) {
+    return 2 + nullCheckCost(curr->ref) + visit(curr->ref) +
+           visit(curr->index) + visit(curr->value);
+  }
   CostType visitArrayLen(ArrayLen* curr) {
     return 1 + nullCheckCost(curr->ref) + visit(curr->ref);
   }

src/ir/effects.h

@@ -1024,6 +1024,15 @@ class EffectAnalyzer {
       // traps when the arg is null or the index out of bounds
       parent.implicitTrap = true;
     }
+    void visitArrayStore(ArrayStore* curr) {
+      if (curr->ref->type.isNull()) {
+        parent.trap = true;
+        return;
+      }
+      parent.writesArray = true;
+      // traps when the arg is null or the index out of bounds
+      parent.implicitTrap = true;
+    }
     void visitArrayLen(ArrayLen* curr) {
       if (curr->ref->type.isNull()) {
         parent.trap = true;

src/ir/possible-contents.cpp

@@ -1102,6 +1102,13 @@ struct InfoCollector
     addChildParentLink(curr->ref, curr);
     addChildParentLink(curr->value, curr);
   }
+  void visitArrayStore(ArrayStore* curr) {
+    if (curr->ref->type == Type::unreachable) {
+      return;
+    }
+    addChildParentLink(curr->ref, curr);
+    addChildParentLink(curr->value, curr);
+  }
 
   void visitArrayLen(ArrayLen* curr) {
     // TODO: optimize when possible (perhaps we can infer a Literal for the
@@ -1739,6 +1746,7 @@ void TNHOracle::scan(Function* func,
     }
     void visitArrayGet(ArrayGet* curr) { notePossibleTrap(curr->ref); }
     void visitArraySet(ArraySet* curr) { notePossibleTrap(curr->ref); }
+    void visitArrayStore(ArrayStore* curr) { notePossibleTrap(curr->ref); }
     void visitArrayLen(ArrayLen* curr) { notePossibleTrap(curr->ref); }
     void visitArrayCopy(ArrayCopy* curr) {
       notePossibleTrap(curr->srcRef);

src/ir/subtype-exprs.h

@@ -408,6 +408,13 @@ struct SubtypingDiscoverer : public OverriddenVisitor<SubType> {
     auto array = curr->ref->type.getHeapType().getArray();
     self()->noteSubtype(curr->value, array.element.type);
   }
+  void visitArrayStore(ArrayStore* curr) {
+    if (!curr->ref->type.isArray()) {
+      return;
+    }
+    auto array = curr->ref->type.getHeapType().getArray();
+    self()->noteSubtype(curr->value, array.element.type);
+  }
   void visitArrayLen(ArrayLen* curr) {}
   void visitArrayCopy(ArrayCopy* curr) {
     if (!curr->srcRef->type.isArray() || !curr->destRef->type.isArray()) {