src/wasm-ir-builder.h - external/github.com/WebAssembly/binaryen - Git at Google

 /*
  * Copyright 2023 WebAssembly Community Group participants
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #ifndef wasm_wasm_ir_builder_h
 #define wasm_wasm_ir_builder_h

 #include <vector>

 #include "ir/names.h"
 #include "support/result.h"
 #include "wasm-builder.h"
 #include "wasm-traversal.h"
 #include "wasm-type.h"
 #include "wasm.h"

 namespace wasm {

 // A utility for constructing valid Binaryen IR from arbitrary valid sequences
 // of WebAssembly instructions. The user is responsible for providing Expression
 // nodes with all of their non-child fields already filled out, and IRBuilder is
 // responsible for setting child fields and finalizing nodes.
 //
 // To use, call CHECK_ERR(visit(...)) or CHECK_ERR(makeXYZ(...)) on each
 // expression in the sequence, then call build().
 //
 // Unlike `Builder`, `IRBuilder` requires referenced module-level items (e.g.
 // globals, tables, functions, etc.) to already exist in the module.
 class IRBuilder : public UnifiedExpressionVisitor<IRBuilder, Result<>> {
 public:
   IRBuilder(Module& wasm) : wasm(wasm), builder(wasm) {}

   // Get the valid Binaryen IR expression representing the sequence of visited
   // instructions. The IRBuilder is reset and can be used with a fresh sequence
   // of instructions after this is called.
   Result<Expression*> build();

   // If the IRBuilder is empty, then it's ready to parse a new self-contained
   // sequence of instructions.
   [[nodiscard]] bool empty() { return scopeStack.empty(); }

   // Call visit() on an existing Expression with its non-child fields
   // initialized to initialize the child fields and refinalize it.
   Result<> visit(Expression*);

   // Like visit, but pushes the expression onto the stack as-is without popping
   // any children or refinalization.
   void push(Expression*);

   // Set the debug location to be attached to the next visited, created, or
   // pushed instruction.
   void setDebugLocation(const std::optional<Function::DebugLocation>&);

   // Give the builder a pointer to the counter tracking the current location in
   // the binary. If this pointer is non-null, the builder will record the binary
   // locations relative to the given code section offset for all instructions
   // and delimiters inside functions.
   void setBinaryLocation(size_t* binaryPos, size_t codeSectionOffset) {
     this->binaryPos = binaryPos;
     this->codeSectionOffset = codeSectionOffset;
   }

   // Set the function used to add scratch locals when constructing an isolated
   // sequence of IR.
   void setFunction(Function* func) { this->func = func; }

   // Handle the boundaries of control flow structures. Users may choose to use
   // the corresponding `makeXYZ` function below instead of `visitXYZStart`, but
   // either way must call `visitEnd` and friends at the appropriate times.
   Result<> visitFunctionStart(Function* func);
   Result<> visitBlockStart(Block* block);
   Result<> visitIfStart(If* iff, Name label = {});
   Result<> visitElse();
   Result<> visitLoopStart(Loop* iff);
   Result<> visitTryStart(Try* tryy, Name label = {});
   Result<> visitCatch(Name tag);
   Result<> visitCatchAll();
   Result<> visitDelegate(Index label);
   Result<> visitTryTableStart(TryTable* trytable, Name label = {});
   Result<> visitEnd();

   // Used to visit break nodes when traversing a single block without its
   // context. The type indicates how many values the break carries to its
   // destination.
   Result<> visitBreakWithType(Break*, Type);
   // Used to visit switch nodes when traversing a single block without its
   // context. The type indicates how many values the switch carries to its
   // destination.
   Result<> visitSwitchWithType(Switch*, Type);

   // Binaryen IR uses names to refer to branch targets, but in general there may
   // be branches to constructs that do not yet have names, so in IRBuilder we
   // use indices to refer to branch targets instead, just as the binary format
   // does. This function converts a branch target name to the correct index.
   //
   // Labels in delegates need special handling because the indexing needs to be
   // relative to the try's enclosing scope rather than the try itself.
   Result<Index> getLabelIndex(Name label, bool inDelegate = false);

   // Instead of calling visit, call makeXYZ to have the IRBuilder allocate the
   // nodes. This is generally safer than calling `visit` because the function
   // signatures ensure that there are no missing fields.
   Result<> makeNop();
   Result<> makeBlock(Name label, Type type);
   Result<> makeIf(Name label, Type type);
   Result<> makeLoop(Name label, Type type);
   Result<> makeBreak(Index label, bool isConditional);
   Result<> makeSwitch(const std::vector<Index>& labels, Index defaultLabel);
   // Unlike Builder::makeCall, this assumes the function already exists.
   Result<> makeCall(Name func, bool isReturn);
   Result<> makeCallIndirect(Name table, HeapType type, bool isReturn);
   Result<> makeLocalGet(Index local);
   Result<> makeLocalSet(Index local);
   Result<> makeLocalTee(Index local);
   Result<> makeGlobalGet(Name global);
   Result<> makeGlobalSet(Name global);
   Result<> makeLoad(unsigned bytes,
                     bool signed_,
                     Address offset,
                     unsigned align,
                     Type type,
                     Name mem);
   Result<> makeStore(
     unsigned bytes, Address offset, unsigned align, Type type, Name mem);
   Result<> makeAtomicLoad(unsigned bytes, Address offset, Type type, Name mem);
   Result<> makeAtomicStore(unsigned bytes, Address offset, Type type, Name mem);
   Result<> makeAtomicRMW(
     AtomicRMWOp op, unsigned bytes, Address offset, Type type, Name mem);
   Result<>
   makeAtomicCmpxchg(unsigned bytes, Address offset, Type type, Name mem);
   Result<> makeAtomicWait(Type type, Address offset, Name mem);
   Result<> makeAtomicNotify(Address offset, Name mem);
   Result<> makeAtomicFence();
   Result<> makeSIMDExtract(SIMDExtractOp op, uint8_t lane);
   Result<> makeSIMDReplace(SIMDReplaceOp op, uint8_t lane);
   Result<> makeSIMDShuffle(const std::array<uint8_t, 16>& lanes);
   Result<> makeSIMDTernary(SIMDTernaryOp op);
   Result<> makeSIMDShift(SIMDShiftOp op);
   Result<>
   makeSIMDLoad(SIMDLoadOp op, Address offset, unsigned align, Name mem);
   Result<> makeSIMDLoadStoreLane(SIMDLoadStoreLaneOp op,
                                  Address offset,
                                  unsigned align,
                                  uint8_t lane,
                                  Name mem);
   Result<> makeMemoryInit(Name data, Name mem);
   Result<> makeDataDrop(Name data);
   Result<> makeMemoryCopy(Name destMem, Name srcMem);
   Result<> makeMemoryFill(Name mem);
   Result<> makeConst(Literal val);
   Result<> makeUnary(UnaryOp op);
   Result<> makeBinary(BinaryOp op);
   Result<> makeSelect(std::optional<Type> type = std::nullopt);
   Result<> makeDrop();
   Result<> makeReturn();
   Result<> makeMemorySize(Name mem);
   Result<> makeMemoryGrow(Name mem);
   Result<> makeUnreachable();
   Result<> makePop(Type type);
   Result<> makeRefNull(HeapType type);
   Result<> makeRefIsNull();
   Result<> makeRefFunc(Name func);
   Result<> makeRefEq();
   Result<> makeTableGet(Name table);
   Result<> makeTableSet(Name table);
   Result<> makeTableSize(Name table);
   Result<> makeTableGrow(Name table);
   Result<> makeTableFill(Name table);
   Result<> makeTableCopy(Name destTable, Name srcTable);
   Result<> makeTableInit(Name elem, Name table);
   Result<> makeTry(Name label, Type type);
   Result<> makeTryTable(Name label,
                         Type type,
                         const std::vector<Name>& tags,
                         const std::vector<Index>& labels,
                         const std::vector<bool>& isRefs);
   Result<> makeThrow(Name tag);
   Result<> makeRethrow(Index label);
   Result<> makeThrowRef();
   Result<> makeTupleMake(uint32_t arity);
   Result<> makeTupleExtract(uint32_t arity, uint32_t index);
   Result<> makeTupleDrop(uint32_t arity);
   Result<> makeRefI31(Shareability share);
   Result<> makeI31Get(bool signed_);
   Result<> makeCallRef(HeapType type, bool isReturn);
   Result<> makeRefTest(Type type);
   Result<> makeRefCast(Type type);
   Result<>
   makeBrOn(Index label, BrOnOp op, Type in = Type::none, Type out = Type::none);
   Result<> makeStructNew(HeapType type);
   Result<> makeStructNewDefault(HeapType type);
   Result<> makeStructGet(HeapType type, Index field, bool signed_);
   Result<> makeStructSet(HeapType type, Index field);
   Result<> makeArrayNew(HeapType type);
   Result<> makeArrayNewDefault(HeapType type);
   Result<> makeArrayNewData(HeapType type, Name data);
   Result<> makeArrayNewElem(HeapType type, Name elem);
   Result<> makeArrayNewFixed(HeapType type, uint32_t arity);
   Result<> makeArrayGet(HeapType type, bool signed_);
   Result<> makeArraySet(HeapType type);
   Result<> makeArrayLen();
   Result<> makeArrayCopy(HeapType destType, HeapType srcType);
   Result<> makeArrayFill(HeapType type);
   Result<> makeArrayInitData(HeapType type, Name data);
   Result<> makeArrayInitElem(HeapType type, Name elem);
   Result<> makeRefAs(RefAsOp op);
   Result<> makeStringNew(StringNewOp op);
   Result<> makeStringConst(Name string);
   Result<> makeStringMeasure(StringMeasureOp op);
   Result<> makeStringEncode(StringEncodeOp op);
   Result<> makeStringConcat();
   Result<> makeStringEq(StringEqOp op);
   Result<> makeStringWTF8Advance();
   Result<> makeStringWTF16Get();
   Result<> makeStringIterNext();
   Result<> makeStringSliceWTF();
   Result<> makeContBind(HeapType contTypeBefore, HeapType contTypeAfter);
   Result<> makeContNew(HeapType ct);
   Result<> makeResume(HeapType ct,
                       const std::vector<Name>& tags,
                       const std::vector<Index>& labels);
   Result<> makeSuspend(Name tag);

   // Private functions that must be public for technical reasons.
   Result<> visitExpression(Expression*);

   // Do not push pops onto the stack since we generate our own pops as necessary
   // when visiting the beginnings of try blocks.
   Result<> visitPop(Pop*) { return Ok{}; }

 private:
   Module& wasm;
   Function* func = nullptr;
   Builder builder;

   // Used for setting DWARF expression locations.
   size_t* binaryPos = nullptr;
   size_t lastBinaryPos = 0;
   size_t codeSectionOffset = 0;

   // The location lacks debug info as it was marked as not having it.
   struct NoDebug : public std::monostate {};
   // The location lacks debug info, but was not marked as not having
   // it, and it can receive it from the parent or its previous sibling
   // (if it has one).
   struct CanReceiveDebug : public std::monostate {};
   using DebugVariant =
     std::variant<NoDebug, CanReceiveDebug, Function::DebugLocation>;

   DebugVariant debugLoc;

   struct ChildPopper;

   void applyDebugLoc(Expression* expr);

   // The context for a single block scope, including the instructions parsed
   // inside that scope so far and the ultimate result type we expect this block
   // to have.
   struct ScopeCtx {
     struct NoScope {};
     struct FuncScope {
       Function* func;
       // Used to determine whether we need to run a fixup after creating the
       // function.
       bool hasSyntheticBlock = false;
       bool hasPop = false;
     };
     struct BlockScope {
       Block* block;
     };
     struct IfScope {
       If* iff;
       Name originalLabel;
     };
     struct ElseScope {
       If* iff;
       Name originalLabel;
     };
     struct LoopScope {
       Loop* loop;
     };
     struct TryScope {
       Try* tryy;
       Name originalLabel;
     };
     struct CatchScope {
       Try* tryy;
       Name originalLabel;
     };
     struct CatchAllScope {
       Try* tryy;
       Name originalLabel;
     };
     struct TryTableScope {
       TryTable* trytable;
       Name originalLabel;
     };
     using Scope = std::variant<NoScope,
                                FuncScope,
                                BlockScope,
                                IfScope,
                                ElseScope,
                                LoopScope,
                                TryScope,
                                CatchScope,
                                CatchAllScope,
                                TryTableScope>;

     // The control flow structure we are building expressions for.
     Scope scope;

     // The branch label name for this scope. Always fresh, never shadowed.
     Name label;
     // For Try/Catch/CatchAll scopes, we need to separately track a label used
     // for branches, since the normal label is only used for delegates.
     Name branchLabel;

     bool labelUsed = false;

     std::vector<Expression*> exprStack;
     // Whether we have seen an unreachable instruction and are in
     // stack-polymorphic unreachable mode.
     bool unreachable = false;

     // The binary location of the start of the scope, used to set debug info.
     size_t startPos = 0;

     ScopeCtx() : scope(NoScope{}) {}
     ScopeCtx(Scope scope) : scope(scope) {}
     ScopeCtx(Scope scope, Name label, bool labelUsed)
       : scope(scope), label(label), labelUsed(labelUsed) {}
     ScopeCtx(Scope scope, Name label, bool labelUsed, Name branchLabel)
       : scope(scope), label(label), branchLabel(branchLabel),
         labelUsed(labelUsed) {}

     static ScopeCtx makeFunc(Function* func) {
       return ScopeCtx(FuncScope{func});
     }
     static ScopeCtx makeBlock(Block* block) {
       return ScopeCtx(BlockScope{block});
     }
     static ScopeCtx makeIf(If* iff, Name originalLabel = {}) {
       return ScopeCtx(IfScope{iff, originalLabel});
     }
     static ScopeCtx
     makeElse(If* iff, Name originalLabel, Name label, bool labelUsed) {
       return ScopeCtx(ElseScope{iff, originalLabel}, label, labelUsed);
     }
     static ScopeCtx makeLoop(Loop* loop) { return ScopeCtx(LoopScope{loop}); }
     static ScopeCtx makeTry(Try* tryy, Name originalLabel = {}) {
       return ScopeCtx(TryScope{tryy, originalLabel});
     }
     static ScopeCtx makeCatch(Try* tryy,
                               Name originalLabel,
                               Name label,
                               bool labelUsed,
                               Name branchLabel) {
       return ScopeCtx(
         CatchScope{tryy, originalLabel}, label, labelUsed, branchLabel);
     }
     static ScopeCtx makeCatchAll(Try* tryy,
                                  Name originalLabel,
                                  Name label,
                                  bool labelUsed,
                                  Name branchLabel) {
       return ScopeCtx(
         CatchAllScope{tryy, originalLabel}, label, labelUsed, branchLabel);
     }
     static ScopeCtx makeTryTable(TryTable* trytable, Name originalLabel = {}) {
       return ScopeCtx(TryTableScope{trytable, originalLabel});
     }

     bool isNone() { return std::get_if<NoScope>(&scope); }
     Function* getFunction() {
       if (auto* funcScope = std::get_if<FuncScope>(&scope)) {
         return funcScope->func;
       }
       return nullptr;
     }
     void noteSyntheticBlock() {
       if (auto* funcScope = std::get_if<FuncScope>(&scope)) {
         funcScope->hasSyntheticBlock = true;
       }
     }
     void notePop() {
       if (auto* funcScope = std::get_if<FuncScope>(&scope)) {
         funcScope->hasPop = true;
       }
     }
     bool needsPopFixup() {
       // If the function has a synthetic block and it has a pop, then it's
       // possible that the pop is inside the synthetic block and we should run
       // the fixup. Determining more precisely that a pop is inside the
       // synthetic block when it is created would be complicated and expensive,
       // so we are conservative here.
       if (auto* funcScope = std::get_if<FuncScope>(&scope)) {
         return funcScope->hasSyntheticBlock && funcScope->hasPop;
       }
       return false;
     }
     Block* getBlock() {
       if (auto* blockScope = std::get_if<BlockScope>(&scope)) {
         return blockScope->block;
       }
       return nullptr;
     }
     If* getIf() {
       if (auto* ifScope = std::get_if<IfScope>(&scope)) {
         return ifScope->iff;
       }
       return nullptr;
     }
     If* getElse() {
       if (auto* elseScope = std::get_if<ElseScope>(&scope)) {
         return elseScope->iff;
       }
       return nullptr;
     }
     Loop* getLoop() {
       if (auto* loopScope = std::get_if<LoopScope>(&scope)) {
         return loopScope->loop;
       }
       return nullptr;
     }
     Try* getTry() {
       if (auto* tryScope = std::get_if<TryScope>(&scope)) {
         return tryScope->tryy;
       }
       return nullptr;
     }
     Try* getCatch() {
       if (auto* catchScope = std::get_if<CatchScope>(&scope)) {
         return catchScope->tryy;
       }
       return nullptr;
     }
     Try* getCatchAll() {
       if (auto* catchAllScope = std::get_if<CatchAllScope>(&scope)) {
         return catchAllScope->tryy;
       }
       return nullptr;
     }
     TryTable* getTryTable() {
       if (auto* tryTableScope = std::get_if<TryTableScope>(&scope)) {
         return tryTableScope->trytable;
       }
       return nullptr;
     }
     Type getResultType() {
       if (auto* func = getFunction()) {
         return func->type.getSignature().results;
       }
       if (auto* block = getBlock()) {
         return block->type;
       }
       if (auto* iff = getIf()) {
         return iff->type;
       }
       if (auto* iff = getElse()) {
         return iff->type;
       }
       if (auto* loop = getLoop()) {
         return loop->type;
       }
       if (auto* tryy = getTry()) {
         return tryy->type;
       }
       if (auto* tryy = getCatch()) {
         return tryy->type;
       }
       if (auto* tryy = getCatchAll()) {
         return tryy->type;
       }
       if (auto* trytable = getTryTable()) {
         return trytable->type;
       }
       WASM_UNREACHABLE("unexpected scope kind");
     }
     Name getOriginalLabel() {
       if (std::get_if<NoScope>(&scope) || getFunction()) {
         return Name{};
       }
       if (auto* block = getBlock()) {
         return block->name;
       }
       if (auto* ifScope = std::get_if<IfScope>(&scope)) {
         return ifScope->originalLabel;
       }
       if (auto* elseScope = std::get_if<ElseScope>(&scope)) {
         return elseScope->originalLabel;
       }
       if (auto* loop = getLoop()) {
         return loop->name;
       }
       if (auto* tryScope = std::get_if<TryScope>(&scope)) {
         return tryScope->originalLabel;
       }
       if (auto* catchScope = std::get_if<CatchScope>(&scope)) {
         return catchScope->originalLabel;
       }
       if (auto* catchAllScope = std::get_if<CatchAllScope>(&scope)) {
         return catchAllScope->originalLabel;
       }
       if (auto* tryTableScope = std::get_if<TryTableScope>(&scope)) {
         return tryTableScope->originalLabel;
       }
       WASM_UNREACHABLE("unexpected scope kind");
     }
   };

   // The stack of block contexts currently being parsed.
   std::vector<ScopeCtx> scopeStack;

   // Map label names to stacks of label depths at which they appear. The
   // relative index of a label name is the current depth minus the top depth on
   // its stack.
   std::unordered_map<Name, std::vector<Index>> labelDepths;

   Name makeFresh(Name label, Index hint = 0) {
     return Names::getValidName(
       label,
       [&](Name candidate) {
         return labelDepths.insert({candidate, {}}).second;
       },
       hint,
       "");
   }

   Index blockHint = 0;
   Index labelHint = 0;

   void pushScope(ScopeCtx scope) {
     if (auto label = scope.getOriginalLabel()) {
       // Assign a fresh label to the scope, if necessary.
       if (!scope.label) {
         scope.label = makeFresh(label);
       }
       // Record the original label to handle references to it correctly.
       labelDepths[label].push_back(scopeStack.size() + 1);
     }
     if (binaryPos) {
       scope.startPos = lastBinaryPos;
       lastBinaryPos = *binaryPos;
     }
     scopeStack.push_back(scope);
   }

   ScopeCtx& getScope() {
     if (scopeStack.empty()) {
       // We are not in a block context, so push a dummy scope.
       scopeStack.push_back({});
     }
     return scopeStack.back();
   }

   Result<ScopeCtx*> getScope(Index label) {
     Index numLabels = scopeStack.size();
     if (!scopeStack.empty() && scopeStack[0].isNone()) {
       --numLabels;
     }
     if (label >= numLabels) {
       return Err{"label index out of bounds"};
     }
     return &scopeStack[scopeStack.size() - 1 - label];
   }

   // Collect the current scope into a single expression. If it has multiple
   // top-level expressions, this requires collecting them into a block. If we
   // are in a block context, we can collect them directly into the destination
   // `block`, but otherwise we will have to allocate a new block.
   Result<Expression*> finishScope(Block* block = nullptr);

   Result<Name> getLabelName(Index label, bool forDelegate = false);
   Result<Name> getDelegateLabelName(Index label) {
     return getLabelName(label, true);
   }
   Result<Index> addScratchLocal(Type);

   struct HoistedVal {
     // The index in the stack of the original value-producing expression.
     Index valIndex;
     // The local.get placed on the stack, if any.
     LocalGet* get;
   };

   // Find the last value-producing expression, if any, and hoist its value to
   // the top of the stack using a scratch local if necessary.
   MaybeResult<HoistedVal> hoistLastValue();
   // Transform the stack as necessary such that the original producer of the
   // hoisted value will be popped along with the final expression that produces
   // the value, if they are different. May only be called directly after
   // hoistLastValue(). `sizeHint` is the size of the type we ultimately want to
   // consume, so if the hoisted value has `sizeHint` elements, it is left intact
   // even if it is a tuple. Otherwise, hoisted tuple values will be broken into
   // pieces.
   Result<> packageHoistedValue(const HoistedVal&, size_t sizeHint = 1);

   Result<Type> getLabelType(Index label);
   Result<Type> getLabelType(Name labelName);

   void dump();
 };

 } // namespace wasm

 #endif // wasm_wasm_ir_builder_h
	/*
	* Copyright 2023 WebAssembly Community Group participants
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#ifndef wasm_wasm_ir_builder_h
	#define wasm_wasm_ir_builder_h

	#include <vector>

	#include "ir/names.h"
	#include "support/result.h"
	#include "wasm-builder.h"
	#include "wasm-traversal.h"
	#include "wasm-type.h"
	#include "wasm.h"

	namespace wasm {

	// A utility for constructing valid Binaryen IR from arbitrary valid sequences
	// of WebAssembly instructions. The user is responsible for providing Expression
	// nodes with all of their non-child fields already filled out, and IRBuilder is
	// responsible for setting child fields and finalizing nodes.
	//
	// To use, call CHECK_ERR(visit(...)) or CHECK_ERR(makeXYZ(...)) on each
	// expression in the sequence, then call build().
	//
	// Unlike `Builder`, `IRBuilder` requires referenced module-level items (e.g.
	// globals, tables, functions, etc.) to already exist in the module.
	class IRBuilder : public UnifiedExpressionVisitor<IRBuilder, Result<>> {
	public:
	IRBuilder(Module& wasm) : wasm(wasm), builder(wasm) {}

	// Get the valid Binaryen IR expression representing the sequence of visited
	// instructions. The IRBuilder is reset and can be used with a fresh sequence
	// of instructions after this is called.
	Result<Expression*> build();

	// If the IRBuilder is empty, then it's ready to parse a new self-contained
	// sequence of instructions.
	[[nodiscard]] bool empty() { return scopeStack.empty(); }

	// Call visit() on an existing Expression with its non-child fields
	// initialized to initialize the child fields and refinalize it.
	Result<> visit(Expression*);

	// Like visit, but pushes the expression onto the stack as-is without popping
	// any children or refinalization.
	void push(Expression*);

	// Set the debug location to be attached to the next visited, created, or
	// pushed instruction.
	void setDebugLocation(const std::optional<Function::DebugLocation>&);

	// Give the builder a pointer to the counter tracking the current location in
	// the binary. If this pointer is non-null, the builder will record the binary
	// locations relative to the given code section offset for all instructions
	// and delimiters inside functions.
	void setBinaryLocation(size_t* binaryPos, size_t codeSectionOffset) {
	this->binaryPos = binaryPos;
	this->codeSectionOffset = codeSectionOffset;
	}

	// Set the function used to add scratch locals when constructing an isolated
	// sequence of IR.
	void setFunction(Function* func) { this->func = func; }

	// Handle the boundaries of control flow structures. Users may choose to use
	// the corresponding `makeXYZ` function below instead of `visitXYZStart`, but
	// either way must call `visitEnd` and friends at the appropriate times.
	Result<> visitFunctionStart(Function* func);
	Result<> visitBlockStart(Block* block);
	Result<> visitIfStart(If* iff, Name label = {});
	Result<> visitElse();
	Result<> visitLoopStart(Loop* iff);
	Result<> visitTryStart(Try* tryy, Name label = {});
	Result<> visitCatch(Name tag);
	Result<> visitCatchAll();
	Result<> visitDelegate(Index label);
	Result<> visitTryTableStart(TryTable* trytable, Name label = {});
	Result<> visitEnd();

	// Used to visit break nodes when traversing a single block without its
	// context. The type indicates how many values the break carries to its
	// destination.
	Result<> visitBreakWithType(Break*, Type);
	// Used to visit switch nodes when traversing a single block without its
	// context. The type indicates how many values the switch carries to its
	// destination.
	Result<> visitSwitchWithType(Switch*, Type);

	// Binaryen IR uses names to refer to branch targets, but in general there may
	// be branches to constructs that do not yet have names, so in IRBuilder we
	// use indices to refer to branch targets instead, just as the binary format
	// does. This function converts a branch target name to the correct index.
	//
	// Labels in delegates need special handling because the indexing needs to be
	// relative to the try's enclosing scope rather than the try itself.
	Result<Index> getLabelIndex(Name label, bool inDelegate = false);

	// Instead of calling visit, call makeXYZ to have the IRBuilder allocate the
	// nodes. This is generally safer than calling `visit` because the function
	// signatures ensure that there are no missing fields.
	Result<> makeNop();
	Result<> makeBlock(Name label, Type type);
	Result<> makeIf(Name label, Type type);
	Result<> makeLoop(Name label, Type type);
	Result<> makeBreak(Index label, bool isConditional);
	Result<> makeSwitch(const std::vector<Index>& labels, Index defaultLabel);
	// Unlike Builder::makeCall, this assumes the function already exists.
	Result<> makeCall(Name func, bool isReturn);
	Result<> makeCallIndirect(Name table, HeapType type, bool isReturn);
	Result<> makeLocalGet(Index local);
	Result<> makeLocalSet(Index local);
	Result<> makeLocalTee(Index local);
	Result<> makeGlobalGet(Name global);
	Result<> makeGlobalSet(Name global);
	Result<> makeLoad(unsigned bytes,
	bool signed_,
	Address offset,
	unsigned align,
	Type type,
	Name mem);
	Result<> makeStore(
	unsigned bytes, Address offset, unsigned align, Type type, Name mem);
	Result<> makeAtomicLoad(unsigned bytes, Address offset, Type type, Name mem);
	Result<> makeAtomicStore(unsigned bytes, Address offset, Type type, Name mem);
	Result<> makeAtomicRMW(
	AtomicRMWOp op, unsigned bytes, Address offset, Type type, Name mem);
	Result<>
	makeAtomicCmpxchg(unsigned bytes, Address offset, Type type, Name mem);
	Result<> makeAtomicWait(Type type, Address offset, Name mem);
	Result<> makeAtomicNotify(Address offset, Name mem);
	Result<> makeAtomicFence();
	Result<> makeSIMDExtract(SIMDExtractOp op, uint8_t lane);
	Result<> makeSIMDReplace(SIMDReplaceOp op, uint8_t lane);
	Result<> makeSIMDShuffle(const std::array<uint8_t, 16>& lanes);
	Result<> makeSIMDTernary(SIMDTernaryOp op);
	Result<> makeSIMDShift(SIMDShiftOp op);
	Result<>
	makeSIMDLoad(SIMDLoadOp op, Address offset, unsigned align, Name mem);
	Result<> makeSIMDLoadStoreLane(SIMDLoadStoreLaneOp op,
	Address offset,
	unsigned align,
	uint8_t lane,
	Name mem);
	Result<> makeMemoryInit(Name data, Name mem);
	Result<> makeDataDrop(Name data);
	Result<> makeMemoryCopy(Name destMem, Name srcMem);
	Result<> makeMemoryFill(Name mem);
	Result<> makeConst(Literal val);
	Result<> makeUnary(UnaryOp op);
	Result<> makeBinary(BinaryOp op);
	Result<> makeSelect(std::optional<Type> type = std::nullopt);
	Result<> makeDrop();
	Result<> makeReturn();
	Result<> makeMemorySize(Name mem);
	Result<> makeMemoryGrow(Name mem);
	Result<> makeUnreachable();
	Result<> makePop(Type type);
	Result<> makeRefNull(HeapType type);
	Result<> makeRefIsNull();
	Result<> makeRefFunc(Name func);
	Result<> makeRefEq();
	Result<> makeTableGet(Name table);
	Result<> makeTableSet(Name table);
	Result<> makeTableSize(Name table);
	Result<> makeTableGrow(Name table);
	Result<> makeTableFill(Name table);
	Result<> makeTableCopy(Name destTable, Name srcTable);
	Result<> makeTableInit(Name elem, Name table);
	Result<> makeTry(Name label, Type type);
	Result<> makeTryTable(Name label,
	Type type,
	const std::vector<Name>& tags,
	const std::vector<Index>& labels,
	const std::vector<bool>& isRefs);
	Result<> makeThrow(Name tag);
	Result<> makeRethrow(Index label);
	Result<> makeThrowRef();
	Result<> makeTupleMake(uint32_t arity);
	Result<> makeTupleExtract(uint32_t arity, uint32_t index);
	Result<> makeTupleDrop(uint32_t arity);
	Result<> makeRefI31(Shareability share);
	Result<> makeI31Get(bool signed_);
	Result<> makeCallRef(HeapType type, bool isReturn);
	Result<> makeRefTest(Type type);
	Result<> makeRefCast(Type type);
	Result<>
	makeBrOn(Index label, BrOnOp op, Type in = Type::none, Type out = Type::none);
	Result<> makeStructNew(HeapType type);
	Result<> makeStructNewDefault(HeapType type);
	Result<> makeStructGet(HeapType type, Index field, bool signed_);
	Result<> makeStructSet(HeapType type, Index field);
	Result<> makeArrayNew(HeapType type);
	Result<> makeArrayNewDefault(HeapType type);
	Result<> makeArrayNewData(HeapType type, Name data);
	Result<> makeArrayNewElem(HeapType type, Name elem);
	Result<> makeArrayNewFixed(HeapType type, uint32_t arity);
	Result<> makeArrayGet(HeapType type, bool signed_);
	Result<> makeArraySet(HeapType type);
	Result<> makeArrayLen();
	Result<> makeArrayCopy(HeapType destType, HeapType srcType);
	Result<> makeArrayFill(HeapType type);
	Result<> makeArrayInitData(HeapType type, Name data);
	Result<> makeArrayInitElem(HeapType type, Name elem);
	Result<> makeRefAs(RefAsOp op);
	Result<> makeStringNew(StringNewOp op);
	Result<> makeStringConst(Name string);
	Result<> makeStringMeasure(StringMeasureOp op);
	Result<> makeStringEncode(StringEncodeOp op);
	Result<> makeStringConcat();
	Result<> makeStringEq(StringEqOp op);
	Result<> makeStringWTF8Advance();
	Result<> makeStringWTF16Get();
	Result<> makeStringIterNext();
	Result<> makeStringSliceWTF();
	Result<> makeContBind(HeapType contTypeBefore, HeapType contTypeAfter);
	Result<> makeContNew(HeapType ct);
	Result<> makeResume(HeapType ct,
	const std::vector<Name>& tags,
	const std::vector<Index>& labels);
	Result<> makeSuspend(Name tag);

	// Private functions that must be public for technical reasons.
	Result<> visitExpression(Expression*);

	// Do not push pops onto the stack since we generate our own pops as necessary
	// when visiting the beginnings of try blocks.
	Result<> visitPop(Pop*) { return Ok{}; }

	private:
	Module& wasm;
	Function* func = nullptr;
	Builder builder;

	// Used for setting DWARF expression locations.
	size_t* binaryPos = nullptr;
	size_t lastBinaryPos = 0;
	size_t codeSectionOffset = 0;

	// The location lacks debug info as it was marked as not having it.
	struct NoDebug : public std::monostate {};
	// The location lacks debug info, but was not marked as not having
	// it, and it can receive it from the parent or its previous sibling
	// (if it has one).
	struct CanReceiveDebug : public std::monostate {};
	using DebugVariant =
	std::variant<NoDebug, CanReceiveDebug, Function::DebugLocation>;

	DebugVariant debugLoc;

	struct ChildPopper;

	void applyDebugLoc(Expression* expr);

	// The context for a single block scope, including the instructions parsed
	// inside that scope so far and the ultimate result type we expect this block
	// to have.
	struct ScopeCtx {
	struct NoScope {};
	struct FuncScope {
	Function* func;
	// Used to determine whether we need to run a fixup after creating the
	// function.
	bool hasSyntheticBlock = false;
	bool hasPop = false;
	};
	struct BlockScope {
	Block* block;
	};
	struct IfScope {
	If* iff;
	Name originalLabel;
	};
	struct ElseScope {
	If* iff;
	Name originalLabel;
	};
	struct LoopScope {
	Loop* loop;
	};
	struct TryScope {
	Try* tryy;
	Name originalLabel;
	};
	struct CatchScope {
	Try* tryy;
	Name originalLabel;
	};
	struct CatchAllScope {
	Try* tryy;
	Name originalLabel;
	};
	struct TryTableScope {
	TryTable* trytable;
	Name originalLabel;
	};
	using Scope = std::variant<NoScope,
	FuncScope,
	BlockScope,
	IfScope,
	ElseScope,
	LoopScope,
	TryScope,
	CatchScope,
	CatchAllScope,
	TryTableScope>;

	// The control flow structure we are building expressions for.
	Scope scope;

	// The branch label name for this scope. Always fresh, never shadowed.
	Name label;
	// For Try/Catch/CatchAll scopes, we need to separately track a label used
	// for branches, since the normal label is only used for delegates.
	Name branchLabel;

	bool labelUsed = false;

	std::vector<Expression*> exprStack;
	// Whether we have seen an unreachable instruction and are in
	// stack-polymorphic unreachable mode.
	bool unreachable = false;

	// The binary location of the start of the scope, used to set debug info.
	size_t startPos = 0;

	ScopeCtx() : scope(NoScope{}) {}
	ScopeCtx(Scope scope) : scope(scope) {}
	ScopeCtx(Scope scope, Name label, bool labelUsed)
	: scope(scope), label(label), labelUsed(labelUsed) {}
	ScopeCtx(Scope scope, Name label, bool labelUsed, Name branchLabel)
	: scope(scope), label(label), branchLabel(branchLabel),
	labelUsed(labelUsed) {}

	static ScopeCtx makeFunc(Function* func) {
	return ScopeCtx(FuncScope{func});
	}
	static ScopeCtx makeBlock(Block* block) {
	return ScopeCtx(BlockScope{block});
	}
	static ScopeCtx makeIf(If* iff, Name originalLabel = {}) {
	return ScopeCtx(IfScope{iff, originalLabel});
	}
	static ScopeCtx
	makeElse(If* iff, Name originalLabel, Name label, bool labelUsed) {
	return ScopeCtx(ElseScope{iff, originalLabel}, label, labelUsed);
	}
	static ScopeCtx makeLoop(Loop* loop) { return ScopeCtx(LoopScope{loop}); }
	static ScopeCtx makeTry(Try* tryy, Name originalLabel = {}) {
	return ScopeCtx(TryScope{tryy, originalLabel});
	}
	static ScopeCtx makeCatch(Try* tryy,
	Name originalLabel,
	Name label,
	bool labelUsed,
	Name branchLabel) {
	return ScopeCtx(
	CatchScope{tryy, originalLabel}, label, labelUsed, branchLabel);
	}
	static ScopeCtx makeCatchAll(Try* tryy,
	Name originalLabel,
	Name label,
	bool labelUsed,
	Name branchLabel) {
	return ScopeCtx(
	CatchAllScope{tryy, originalLabel}, label, labelUsed, branchLabel);
	}
	static ScopeCtx makeTryTable(TryTable* trytable, Name originalLabel = {}) {
	return ScopeCtx(TryTableScope{trytable, originalLabel});
	}

	bool isNone() { return std::get_if<NoScope>(&scope); }
	Function* getFunction() {
	if (auto* funcScope = std::get_if<FuncScope>(&scope)) {
	return funcScope->func;
	}
	return nullptr;
	}
	void noteSyntheticBlock() {
	if (auto* funcScope = std::get_if<FuncScope>(&scope)) {
	funcScope->hasSyntheticBlock = true;
	}
	}
	void notePop() {
	if (auto* funcScope = std::get_if<FuncScope>(&scope)) {
	funcScope->hasPop = true;
	}
	}
	bool needsPopFixup() {
	// If the function has a synthetic block and it has a pop, then it's
	// possible that the pop is inside the synthetic block and we should run
	// the fixup. Determining more precisely that a pop is inside the
	// synthetic block when it is created would be complicated and expensive,
	// so we are conservative here.
	if (auto* funcScope = std::get_if<FuncScope>(&scope)) {
	return funcScope->hasSyntheticBlock && funcScope->hasPop;
	}
	return false;
	}
	Block* getBlock() {
	if (auto* blockScope = std::get_if<BlockScope>(&scope)) {
	return blockScope->block;
	}
	return nullptr;
	}
	If* getIf() {
	if (auto* ifScope = std::get_if<IfScope>(&scope)) {
	return ifScope->iff;
	}
	return nullptr;
	}
	If* getElse() {
	if (auto* elseScope = std::get_if<ElseScope>(&scope)) {
	return elseScope->iff;
	}
	return nullptr;
	}
	Loop* getLoop() {
	if (auto* loopScope = std::get_if<LoopScope>(&scope)) {
	return loopScope->loop;
	}
	return nullptr;
	}
	Try* getTry() {
	if (auto* tryScope = std::get_if<TryScope>(&scope)) {
	return tryScope->tryy;
	}
	return nullptr;
	}
	Try* getCatch() {
	if (auto* catchScope = std::get_if<CatchScope>(&scope)) {
	return catchScope->tryy;
	}
	return nullptr;
	}
	Try* getCatchAll() {
	if (auto* catchAllScope = std::get_if<CatchAllScope>(&scope)) {
	return catchAllScope->tryy;
	}
	return nullptr;
	}
	TryTable* getTryTable() {
	if (auto* tryTableScope = std::get_if<TryTableScope>(&scope)) {
	return tryTableScope->trytable;
	}
	return nullptr;
	}
	Type getResultType() {
	if (auto* func = getFunction()) {
	return func->type.getSignature().results;
	}
	if (auto* block = getBlock()) {
	return block->type;
	}
	if (auto* iff = getIf()) {
	return iff->type;
	}
	if (auto* iff = getElse()) {
	return iff->type;
	}
	if (auto* loop = getLoop()) {
	return loop->type;
	}
	if (auto* tryy = getTry()) {
	return tryy->type;
	}
	if (auto* tryy = getCatch()) {
	return tryy->type;
	}
	if (auto* tryy = getCatchAll()) {
	return tryy->type;
	}
	if (auto* trytable = getTryTable()) {
	return trytable->type;
	}
	WASM_UNREACHABLE("unexpected scope kind");
	}
	Name getOriginalLabel() {
	if (std::get_if<NoScope>(&scope) \|\| getFunction()) {
	return Name{};
	}
	if (auto* block = getBlock()) {
	return block->name;
	}
	if (auto* ifScope = std::get_if<IfScope>(&scope)) {
	return ifScope->originalLabel;
	}
	if (auto* elseScope = std::get_if<ElseScope>(&scope)) {
	return elseScope->originalLabel;
	}
	if (auto* loop = getLoop()) {
	return loop->name;
	}
	if (auto* tryScope = std::get_if<TryScope>(&scope)) {
	return tryScope->originalLabel;
	}
	if (auto* catchScope = std::get_if<CatchScope>(&scope)) {
	return catchScope->originalLabel;
	}
	if (auto* catchAllScope = std::get_if<CatchAllScope>(&scope)) {
	return catchAllScope->originalLabel;
	}
	if (auto* tryTableScope = std::get_if<TryTableScope>(&scope)) {
	return tryTableScope->originalLabel;
	}
	WASM_UNREACHABLE("unexpected scope kind");
	}
	};

	// The stack of block contexts currently being parsed.
	std::vector<ScopeCtx> scopeStack;

	// Map label names to stacks of label depths at which they appear. The
	// relative index of a label name is the current depth minus the top depth on
	// its stack.
	std::unordered_map<Name, std::vector<Index>> labelDepths;

	Name makeFresh(Name label, Index hint = 0) {
	return Names::getValidName(
	label,
	[&](Name candidate) {
	return labelDepths.insert({candidate, {}}).second;
	},
	hint,
	"");
	}

	Index blockHint = 0;
	Index labelHint = 0;

	void pushScope(ScopeCtx scope) {
	if (auto label = scope.getOriginalLabel()) {
	// Assign a fresh label to the scope, if necessary.
	if (!scope.label) {
	scope.label = makeFresh(label);
	}
	// Record the original label to handle references to it correctly.
	labelDepths[label].push_back(scopeStack.size() + 1);
	}
	if (binaryPos) {
	scope.startPos = lastBinaryPos;
	lastBinaryPos = *binaryPos;
	}
	scopeStack.push_back(scope);
	}

	ScopeCtx& getScope() {
	if (scopeStack.empty()) {
	// We are not in a block context, so push a dummy scope.
	scopeStack.push_back({});
	}
	return scopeStack.back();
	}

	Result<ScopeCtx*> getScope(Index label) {
	Index numLabels = scopeStack.size();
	if (!scopeStack.empty() && scopeStack[0].isNone()) {
	--numLabels;
	}
	if (label >= numLabels) {
	return Err{"label index out of bounds"};
	}
	return &scopeStack[scopeStack.size() - 1 - label];
	}

	// Collect the current scope into a single expression. If it has multiple
	// top-level expressions, this requires collecting them into a block. If we
	// are in a block context, we can collect them directly into the destination
	// `block`, but otherwise we will have to allocate a new block.
	Result<Expression> finishScope(Block block = nullptr);

	Result<Name> getLabelName(Index label, bool forDelegate = false);
	Result<Name> getDelegateLabelName(Index label) {
	return getLabelName(label, true);
	}
	Result<Index> addScratchLocal(Type);

	struct HoistedVal {
	// The index in the stack of the original value-producing expression.
	Index valIndex;
	// The local.get placed on the stack, if any.
	LocalGet* get;
	};

	// Find the last value-producing expression, if any, and hoist its value to
	// the top of the stack using a scratch local if necessary.
	MaybeResult<HoistedVal> hoistLastValue();
	// Transform the stack as necessary such that the original producer of the
	// hoisted value will be popped along with the final expression that produces
	// the value, if they are different. May only be called directly after
	// hoistLastValue(). `sizeHint` is the size of the type we ultimately want to
	// consume, so if the hoisted value has `sizeHint` elements, it is left intact
	// even if it is a tuple. Otherwise, hoisted tuple values will be broken into
	// pieces.
	Result<> packageHoistedValue(const HoistedVal&, size_t sizeHint = 1);

	Result<Type> getLabelType(Index label);
	Result<Type> getLabelType(Name labelName);

	void dump();
	};

	} // namespace wasm

	#endif // wasm_wasm_ir_builder_h