[EH] Support reading/writing of delegate

src/ir/ExpressionAnalyzer.cpp

@@ -17,6 +17,7 @@
 #include "ir/iteration.h"
 #include "ir/load-utils.h"
 #include "ir/utils.h"
+#include "shared-constants.h"
 #include "support/hash.h"
 #include "support/small_vector.h"
 #include "wasm-traversal.h"
@@ -261,6 +262,9 @@ size_t ExpressionAnalyzer::hash(Expression* curr) {
 
     Hasher(Expression* curr) {
       stack.push_back(curr);
+      // DELEGATE_CALLER_TARGET is a fake target used to denote delegating to
+      // the caller. Add it here to prevent the unknown name error.
+      noteScopeName(DELEGATE_CALLER_TARGET);
 
       while (stack.size() > 0) {
         curr = stack.back();
@@ -327,13 +331,15 @@ size_t ExpressionAnalyzer::hash(Expression* curr) {
       }
     }
     void visitScopeName(Name curr) {
-      // Names are relative, we give the same hash for
-      // (block $x (br $x))
-      // (block $y (br $y))
-      static_assert(sizeof(Index) == sizeof(int32_t),
-                    "wasm64 will need changes here");
-      assert(internalNames.find(curr) != internalNames.end());
-      rehash(digest, internalNames[curr]);
+      if (curr.is()) { // try's delegate target can be null
+        // Names are relative, we give the same hash for
+        // (block $x (br $x))
+        // (block $y (br $y))
+        static_assert(sizeof(Index) == sizeof(int32_t),
+                      "wasm64 will need changes here");
+        assert(internalNames.find(curr) != internalNames.end());
+        rehash(digest, internalNames[curr]);
+      }
     }
     void visitNonScopeName(Name curr) { rehash(digest, uint64_t(curr.str)); }
     void visitType(Type curr) { rehash(digest, curr.getID()); }

src/ir/branch-utils.h

@@ -40,9 +40,9 @@ inline bool isBranchReachable(Expression* expr) {
   return true;
 }
 
-// Perform a generic operation on uses of scope names (branch targets) in an
-// expression. The provided function receives a Name& which it can modify if it
-// needs to.
+// Perform a generic operation on uses of scope names (branch + delegate
+// targets) in an expression. The provided function receives a Name& which it
+// can modify if it needs to.
 template<typename T> void operateOnScopeNameUses(Expression* expr, T func) {
 #define DELEGATE_ID expr->_id
 
@@ -83,7 +83,7 @@ void operateOnScopeNameUsesAndSentTypes(Expression* expr, T func) {
     } else if (auto* br = expr->dynCast<BrOn>()) {
       func(name, br->getCastType());
     } else {
-      WASM_UNREACHABLE("bad br type");
+      assert(expr->is<Try>()); // delegate
     }
   });
 }
@@ -135,6 +135,46 @@ inline bool replacePossibleTarget(Expression* branch, Name from, Name to) {
   return worked;
 }
 
+// Replace all delegate targets within the given AST.
+inline void replaceDelegateTargets(Expression* ast, Name from, Name to) {
+  struct Replacer
+    : public PostWalker<Replacer, UnifiedExpressionVisitor<Replacer>> {
+    Name from, to;
+    Replacer(Name from, Name to) : from(from), to(to) {}
+    void visitExpression(Expression* curr) {
+      if (curr->is<Try>()) {
+        operateOnScopeNameUses(curr, [&](Name& name) {
+          if (name == from) {
+            name = to;
+          }
+        });
+      }
+    }
+  };
+  Replacer replacer(from, to);
+  replacer.walk(ast);
+}
+
+// Replace all branch targets within the given AST.
+inline void replaceBranchTargets(Expression* ast, Name from, Name to) {
+  struct Replacer
+    : public PostWalker<Replacer, UnifiedExpressionVisitor<Replacer>> {
+    Name from, to;
+    Replacer(Name from, Name to) : from(from), to(to) {}
+    void visitExpression(Expression* curr) {
+      if (Properties::isBranch(curr)) {
+        operateOnScopeNameUses(curr, [&](Name& name) {
+          if (name == from) {
+            name = to;
+          }
+        });
+      }
+    }
+  };
+  Replacer replacer(from, to);
+  replacer.walk(ast);
+}
+
 // Returns the set of targets to which we branch that are
 // outside of an expression.
 inline NameSet getExitingBranches(Expression* ast) {

src/ir/properties.h

@@ -69,13 +69,15 @@ inline bool isControlFlowStructure(Expression* curr) {
          curr->is<Try>();
 }
 
-// Check if an expression is a control flow construct with a name,
-// which implies it may have breaks to it.
+// Check if an expression is a control flow construct with a name, which implies
+// it may have breaks or delegates to it.
 inline bool isNamedControlFlow(Expression* curr) {
   if (auto* block = curr->dynCast<Block>()) {
     return block->name.is();
   } else if (auto* loop = curr->dynCast<Loop>()) {
     return loop->name.is();
+  } else if (auto* try_ = curr->dynCast<Try>()) {
+    return try_->name.is();
   }
   return false;
 }
@@ -104,6 +106,10 @@ inline bool isConstantExpression(const Expression* curr) {
   return false;
 }
 
+inline bool isBranch(const Expression* curr) {
+  return curr->is<Break>() || curr->is<Switch>() || curr->is<BrOn>();
+}
+
 inline Literal getLiteral(const Expression* curr) {
   if (auto* c = curr->dynCast<Const>()) {
     return c->value;

src/passes/Poppify.cpp

@@ -128,6 +128,7 @@ struct Poppifier : BinaryenIRWriter<Poppifier> {
   void emitIfElse(If* curr);
   void emitCatch(Try* curr, Index i);
   void emitCatchAll(Try* curr);
+  void emitDelegate(Try* curr);
   void emitScopeEnd(Expression* curr);
   void emitFunctionEnd();
   void emitUnreachable();
@@ -272,6 +273,13 @@ void Poppifier::emitCatchAll(Try* curr) {
   scopeStack.emplace_back(Scope::Catch);
 }
 
+void Poppifier::emitDelegate(Try* curr) {
+  auto& scope = scopeStack.back();
+  assert(scope.kind == Scope::Try);
+  patchScope(curr->body);
+  scopeStack.back().instrs.push_back(curr);
+}
+
 void Poppifier::emitScopeEnd(Expression* curr) {
   switch (scopeStack.back().kind) {
     case Scope::Block:

src/passes/Print.cpp

@@ -1764,6 +1764,10 @@ struct PrintExpressionContents
   void visitRefEq(RefEq* curr) { printMedium(o, "ref.eq"); }
   void visitTry(Try* curr) {
     printMedium(o, "try");
+    if (curr->name.is()) {
+      o << ' ';
+      printName(curr->name, o);
+    }
     if (curr->type.isConcrete()) {
       o << ' ' << ResultType(curr->type);
     }
@@ -1955,6 +1959,9 @@ struct PrintSExpression : public OverriddenVisitor<PrintSExpression> {
   Function::DebugLocation lastPrintedLocation;
   bool debugInfo;
 
+  // Used to print delegate's depth argument when it throws to the caller
+  int controlFlowDepth = 0;
+
   PrintSExpression(std::ostream& o) : o(o) {
     setMinify(false);
     if (!full) {
@@ -2100,6 +2107,9 @@ struct PrintSExpression : public OverriddenVisitor<PrintSExpression> {
         break; // that's all we can recurse, start to unwind
       }
     }
+
+    int startControlFlowDepth = controlFlowDepth;
+    controlFlowDepth += stack.size();
     auto* top = stack.back();
     while (stack.size() > 0) {
       curr = stack.back();
@@ -2129,8 +2139,10 @@ struct PrintSExpression : public OverriddenVisitor<PrintSExpression> {
         o << ' ' << curr->name;
       }
     }
+    controlFlowDepth = startControlFlowDepth;
   }
   void visitIf(If* curr) {
+    controlFlowDepth++;
     o << '(';
     printExpressionContents(curr);
     incIndent();
@@ -2147,8 +2159,10 @@ struct PrintSExpression : public OverriddenVisitor<PrintSExpression> {
     if (full) {
       o << " ;; end if";
     }
+    controlFlowDepth--;
   }
   void visitLoop(Loop* curr) {
+    controlFlowDepth++;
     o << '(';
     printExpressionContents(curr);
     incIndent();
@@ -2160,6 +2174,7 @@ struct PrintSExpression : public OverriddenVisitor<PrintSExpression> {
         o << ' ' << curr->name;
       }
     }
+    controlFlowDepth--;
   }
   void visitBreak(Break* curr) {
     o << '(';
@@ -2490,13 +2505,28 @@ struct PrintSExpression : public OverriddenVisitor<PrintSExpression> {
   //  (do
   //   ...
   //  )
-  //  (catch
-  //   ...
+  //  (catch $e
+  //    ...
+  //  )
+  //  ...
+  //  (catch_all
+  //    ...
   //  )
   // )
-  // The parenthesis wrapping 'catch' is just a syntax and does not affect
-  // nested depths of instructions within.
+  // The parenthesis wrapping do/catch/catch_all is just a syntax and does not
+  // affect nested depths of instructions within.
+  //
+  // try-delegate is written in the forded format as
+  // (try
+  //  (do
+  //    ...
+  //  )
+  //  (delegate $label)
+  // )
+  // When the 'delegate' delegates to the caller, we write the argument as an
+  // immediate.
   void visitTry(Try* curr) {
+    controlFlowDepth++;
     o << '(';
     printExpressionContents(curr);
     incIndent();
@@ -2521,12 +2551,26 @@ struct PrintSExpression : public OverriddenVisitor<PrintSExpression> {
     if (curr->hasCatchAll()) {
       doIndent(o, indent);
       printDebugDelimiterLocation(curr, curr->catchEvents.size());
-      o << "(catch_all";
+      o << '(';
+      printMedium(o, "catch_all");
       incIndent();
       maybePrintImplicitBlock(curr->catchBodies.back(), true);
       decIndent();
       o << "\n";
     }
+    controlFlowDepth--;
+
+    if (curr->isDelegate()) {
+      doIndent(o, indent);
+      o << '(';
+      printMedium(o, "delegate ");
+      if (curr->delegateTarget == DELEGATE_CALLER_TARGET) {
+        o << controlFlowDepth;
+      } else {
+        printName(curr->delegateTarget, o);
+      }
+      o << ")\n";
+    }
     decIndent();
     if (full) {
       o << " ;; end try";
@@ -2913,6 +2957,7 @@ struct PrintSExpression : public OverriddenVisitor<PrintSExpression> {
       } else {
         printFullLine(curr->body);
       }
+      assert(controlFlowDepth == 0);
     } else {
       // Print the stack IR.
       printStackIR(curr->stackIR.get(), o, curr);
@@ -3324,6 +3369,11 @@ printStackInst(StackInst* inst, std::ostream& o, Function* func) {
       printMedium(o, "catch_all");
       break;
     }
+    case StackInst::Delegate: {
+      printMedium(o, "delegate ");
+      printName(inst->origin->cast<Try>()->delegateTarget, o);
+      break;
+    }
     default:
       WASM_UNREACHABLE("unexpeted op");
   }
@@ -3339,6 +3389,7 @@ printStackIR(StackIR* ir, std::ostream& o, Function* func) {
     }
   };
 
+  int controlFlowDepth = 0;
   // Stack to track indices of catches within a try
   SmallVector<Index, 4> catchIndexStack;
   for (Index i = 0; i < (*ir).size(); i++) {
@@ -3364,6 +3415,7 @@ printStackIR(StackIR* ir, std::ostream& o, Function* func) {
       case StackInst::BlockBegin:
       case StackInst::IfBegin:
       case StackInst::LoopBegin: {
+        controlFlowDepth++;
         doIndent();
         PrintExpressionContents(func, o).visit(inst->origin);
         indent++;
@@ -3375,6 +3427,7 @@ printStackIR(StackIR* ir, std::ostream& o, Function* func) {
       case StackInst::BlockEnd:
       case StackInst::IfEnd:
       case StackInst::LoopEnd: {
+        controlFlowDepth--;
         indent--;
         doIndent();
         printMedium(o, "end");
@@ -3403,11 +3456,25 @@ printStackIR(StackIR* ir, std::ostream& o, Function* func) {
         indent++;
         break;
       }
+      case StackInst::Delegate: {
+        controlFlowDepth--;
+        indent--;
+        doIndent();
+        printMedium(o, "delegate ");
+        Try* curr = inst->origin->cast<Try>();
+        if (curr->delegateTarget == DELEGATE_CALLER_TARGET) {
+          o << controlFlowDepth;
+        } else {
+          printName(curr->delegateTarget, o);
+        }
+        break;
+      }
       default:
         WASM_UNREACHABLE("unexpeted op");
     }
     std::cout << '\n';
   }
+  assert(controlFlowDepth == 0);
   return o;
 }
 

src/passes/RemoveUnusedNames.cpp

@@ -83,6 +83,8 @@ struct RemoveUnusedNames
     }
   }
 
+  void visitTry(Try* curr) { handleBreakTarget(curr->name); }
+
   void visitFunction(Function* curr) { assert(branchesSeen.empty()); }
 };
 

src/passes/StackIR.cpp

@@ -258,6 +258,7 @@ class StackIROptimizer {
       case StackInst::LoopEnd:
       case StackInst::Catch:
       case StackInst::CatchAll:
+      case StackInst::Delegate:
       case StackInst::TryEnd: {
         return true;
       }
@@ -284,7 +285,8 @@ class StackIROptimizer {
       case StackInst::BlockEnd:
       case StackInst::IfEnd:
       case StackInst::LoopEnd:
-      case StackInst::TryEnd: {
+      case StackInst::TryEnd:
+      case StackInst::Delegate: {
         return true;
       }
       default: { return false; }

src/shared-constants.h

@@ -60,6 +60,7 @@ extern Name CASE;
 extern Name BR;
 extern Name FUNCREF;
 extern Name FAKE_RETURN;
+extern Name DELEGATE_CALLER_TARGET;
 extern Name MUT;
 extern Name SPECTEST;
 extern Name PRINT;