Add atomic loads and stores (#1077)

Add IR, wast and binary support for atomic loads and stores.

Currently all IR generated by means other than parsing wast and binary files always generates non-atomic accesses, and optimizations have not yet been made aware of atomics, so they are certainly not ready to be used yet.

Author: dschuff

src/asm2wasm.h

@@ -1772,6 +1772,7 @@ Function* Asm2WasmBuilder::processFunction(Ref ast) {
       assert(views.find(heap) != views.end());
       View& view = views[heap];
       auto ret = allocator.alloc<Store>();
+      ret->isAtomic = false;
       ret->bytes = view.bytes;
       ret->offset = 0;
       ret->align = view.bytes;
@@ -1843,6 +1844,7 @@ Function* Asm2WasmBuilder::processFunction(Ref ast) {
       assert(views.find(heap) != views.end());
       View& view = views[heap];
       auto ret = allocator.alloc<Load>();
+      ret->isAtomic = false;
       ret->bytes = view.bytes;
       ret->signed_ = view.signed_;
       ret->offset = 0;

src/binaryen-c.cpp

@@ -549,7 +549,7 @@ BinaryenExpressionRef BinaryenLoad(BinaryenModuleRef module, uint32_t bytes, int
     auto id = noteExpression(ret);
     std::cout << "  expressions[" << id << "] = BinaryenLoad(the_module, " << bytes << ", " << int(signed_) << ", " << offset << ", " << align << ", " << type << ", expressions[" << expressions[ptr] << "]);\n";
   }
-
+  ret->isAtomic = false;
   ret->bytes = bytes;
   ret->signed_ = !!signed_;
   ret->offset = offset;
@@ -566,7 +566,7 @@ BinaryenExpressionRef BinaryenStore(BinaryenModuleRef module, uint32_t bytes, ui
     auto id = noteExpression(ret);
     std::cout << "  expressions[" << id << "] = BinaryenStore(the_module, " << bytes << ", " << offset << ", " << align << ", expressions[" << expressions[ptr] << "], expressions[" << expressions[value] << "], " << type << ");\n";
   }
-
+  ret->isAtomic = false;
   ret->bytes = bytes;
   ret->offset = offset;
   ret->align = align ? align : bytes;

src/compiler-support.h

@@ -27,7 +27,7 @@
 
 // If control flow reaches the point of the WASM_UNREACHABLE(), the program is
 // undefined.
-#if __has_builtin(__builtin_unreachable)
+#if __has_builtin(__builtin_unreachable) && defined(NDEBUG)
 # define WASM_UNREACHABLE() __builtin_unreachable()
 #elif defined(_MSC_VER)
 # define WASM_UNREACHABLE() __assume(false)

src/passes/Print.cpp

@@ -296,7 +296,9 @@ struct PrintSExpression : public Visitor<PrintSExpression> {
   }
   void visitLoad(Load *curr) {
     o << '(';
-    prepareColor(o) << printWasmType(curr->type) << ".load";
+    prepareColor(o) << printWasmType(curr->type);
+    if (curr->isAtomic) o << ".atomic";
+    o << ".load";
     if (curr->bytes < 4 || (curr->type == i64 && curr->bytes < 8)) {
       if (curr->bytes == 1) {
         o << '8';
@@ -322,7 +324,9 @@ struct PrintSExpression : public Visitor<PrintSExpression> {
   }
   void visitStore(Store *curr) {
     o << '(';
-    prepareColor(o) << printWasmType(curr->valueType) << ".store";
+    prepareColor(o) << printWasmType(curr->valueType);
+    if (curr->isAtomic) o << ".atomic";
+    o << ".store";
     if (curr->bytes < 4 || (curr->valueType == i64 && curr->bytes < 8)) {
       if (curr->bytes == 1) {
         o << '8';

src/s2wasm.h

@@ -920,6 +920,7 @@ class S2WasmBuilder {
     auto makeLoad = [&](WasmType type) {
       skipComma();
       auto curr = allocator->alloc<Load>();
+      curr->isAtomic = false;
       curr->type = type;
       int32_t bytes = getInt() / CHAR_BIT;
       curr->bytes = bytes > 0 ? bytes : getWasmTypeSize(type);
@@ -939,6 +940,7 @@ class S2WasmBuilder {
     };
     auto makeStore = [&](WasmType type) {
       auto curr = allocator->alloc<Store>();
+      curr->isAtomic = false;
       curr->valueType = type;
       s += strlen("store");
       if(!isspace(*s)) {

src/wasm-binary.h

@@ -506,7 +506,26 @@ enum ASTNodes {
   I32ReinterpretF32 = 0xbc,
   I64ReinterpretF64 = 0xbd,
   F32ReinterpretI32 = 0xbe,
-  F64ReinterpretI64 = 0xbf
+  F64ReinterpretI64 = 0xbf,
+
+  AtomicPrefix = 0xfe
+};
+
+enum AtomicOpcodes {
+  I32AtomicLoad = 0x10,
+  I64AtomicLoad = 0x11,
+  I32AtomicLoad8U = 0x12,
+  I32AtomicLoad16U = 0x13,
+  I64AtomicLoad8U = 0x14,
+  I64AtomicLoad16U = 0x15,
+  I64AtomicLoad32U = 0x16,
+  I32AtomicStore = 0x17,
+  I64AtomicStore = 0x18,
+  I32AtomicStore8 = 0x19,
+  I32AtomicStore16 = 0x1a,
+  I64AtomicStore8 = 0x1b,
+  I64AtomicStore16 = 0x1c,
+  I64AtomicStore32 = 0x1d
 };
 
 enum MemoryAccess {
@@ -812,8 +831,8 @@ class WasmBinaryBuilder {
   void visitGetGlobal(GetGlobal *curr);
   void visitSetGlobal(SetGlobal *curr);
   void readMemoryAccess(Address& alignment, size_t bytes, Address& offset);
-  bool maybeVisitLoad(Expression*& out, uint8_t code);
-  bool maybeVisitStore(Expression*& out, uint8_t code);
+  bool maybeVisitLoad(Expression*& out, uint8_t code, bool isAtomic);
+  bool maybeVisitStore(Expression*& out, uint8_t code, bool isAtomic);
   bool maybeVisitConst(Expression*& out, uint8_t code);
   bool maybeVisitUnary(Expression*& out, uint8_t code);
   bool maybeVisitBinary(Expression*& out, uint8_t code);

src/wasm-builder.h

@@ -188,12 +188,14 @@ class Builder {
   }
   Load* makeLoad(unsigned bytes, bool signed_, uint32_t offset, unsigned align, Expression *ptr, WasmType type) {
     auto* ret = allocator.alloc<Load>();
+    ret->isAtomic = false;
     ret->bytes = bytes; ret->signed_ = signed_; ret->offset = offset; ret->align = align; ret->ptr = ptr;
     ret->type = type;
     return ret;
   }
   Store* makeStore(unsigned bytes, uint32_t offset, unsigned align, Expression *ptr, Expression *value, WasmType type) {
     auto* ret = allocator.alloc<Store>();
+    ret->isAtomic = false;
     ret->bytes = bytes; ret->offset = offset; ret->align = align; ret->ptr = ptr; ret->value = value; ret->valueType = type;
     ret->finalize();
     assert(isConcreteWasmType(ret->value->type) ? ret->value->type == type : true);

src/wasm-s-parser.h

@@ -175,8 +175,8 @@ class SExpressionWasmBuilder {
   Expression* makeBlock(Element& s);
   Expression* makeThenOrElse(Element& s);
   Expression* makeConst(Element& s, WasmType type);
-  Expression* makeLoad(Element& s, WasmType type);
-  Expression* makeStore(Element& s, WasmType type);
+  Expression* makeLoad(Element& s, WasmType type, bool isAtomic);
+  Expression* makeStore(Element& s, WasmType type, bool isAtomic);
   Expression* makeIf(Element& s);
   Expression* makeMaybeBlock(Element& s, size_t i, WasmType type);
   Expression* makeLoop(Element& s);

src/wasm.h

@@ -177,6 +177,7 @@ class Expression {
     HostId,
     NopId,
     UnreachableId,
+    AtomicRMWId,
     NumExpressionIds
   };
   Id _id;
@@ -398,6 +399,7 @@ class Load : public SpecificExpression<Expression::LoadId> {
   bool signed_;
   Address offset;
   Address align;
+  bool isAtomic;
   Expression* ptr;
 
   // type must be set during creation, cannot be inferred
@@ -413,6 +415,7 @@ class Store : public SpecificExpression<Expression::StoreId> {
   uint8_t bytes;
   Address offset;
   Address align;
+  bool isAtomic;
   Expression* ptr;
   Expression* value;
   WasmType valueType; // the store never returns a value
@@ -511,6 +514,13 @@ class Unreachable : public SpecificExpression<Expression::UnreachableId> {
   Unreachable(MixedArena& allocator) : Unreachable() {}
 };
 
+class AtomicRMW : public SpecificExpression<Expression::AtomicRMWId> {
+ public:
+  AtomicRMW() {}
+  AtomicRMW(MixedArena& allocator) : AtomicRMW() {}
+  bool finalize();
+};
+
 // Globals
 
 class Function {