[V8][Wasm] Removes references to finally in wasm.

src/wasm/ast-decoder.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/signature.h"
 
 #include "src/bit-vector.h"
 #include "src/flags.h"
 #include "src/handles.h"
 #include "src/zone-containers.h"
@@ skipping 50 matching lines @@
   }
 };
 
 // An entry on the value stack.
 struct Value {
   const byte* pc;
   TFNode* node;
   LocalType type;
 };
 
-// An entry on the control stack (i.e. if, block, loop).
+struct Control;
+
+// An entry on the control stack (i.e. if, block, loop, try).
 struct Control {
   const byte* pc;
-  int stack_depth;         // stack height at the beginning of the construct.
-  SsaEnv* end_env;         // end environment for the construct.
-  SsaEnv* false_env;       // false environment (only for if).
-  SsaEnv* catch_env;       // catch environment (only for try with catch).
-  SsaEnv* finish_try_env;  // the environment where a try with finally lives.
-  TFNode* node;            // result node for the construct.
-  LocalType type;          // result type for the construct.
-  bool is_loop;            // true if this is the inner label of a loop.
+  int stack_depth;    // stack height at the beginning of the construct.
+  SsaEnv* end_env;    // end environment for the construct.
+  SsaEnv* false_env;  // false environment (only for if).
+  SsaEnv* catch_env;  // catch environment (only for try).
+  TFNode* node;       // result node for the construct.
+  LocalType type;     // result type for the construct.
+  bool is_loop;       // true if this is the inner label of a loop.
 
   bool is_if() const { return *pc == kExprIf; }
 
-  bool is_try() const {
-    return *pc == kExprTryCatch || *pc == kExprTryCatchFinally ||
-           *pc == kExprTryFinally;
-  }
-
-  bool has_catch() const {
-    return *pc == kExprTryCatch || *pc == kExprTryCatchFinally;
-  }
-
-  bool has_finally() const {
-    return *pc == kExprTryCatchFinally || *pc == kExprTryFinally;
-  }
+  bool is_try() const { return *pc == kExprTry; }
 
   // Named constructors.
   static Control Block(const byte* pc, int stack_depth, SsaEnv* end_env) {
-    return {pc,      stack_depth, end_env, nullptr, nullptr,
+    return {pc,      stack_depth, end_env, nullptr,
             nullptr, nullptr,     kAstEnd, false};
   }
 
   static Control If(const byte* pc, int stack_depth, SsaEnv* end_env,
                     SsaEnv* false_env) {
-    return {pc,      stack_depth, end_env,  false_env, nullptr,
+    return {pc,      stack_depth, end_env,  false_env,
             nullptr, nullptr,     kAstStmt, false};
   }
 
   static Control Loop(const byte* pc, int stack_depth, SsaEnv* end_env) {
-    return {pc,      stack_depth, end_env, nullptr, nullptr,
-            nullptr, nullptr,     kAstEnd, true};
+    return {pc, stack_depth, end_env, nullptr, nullptr, nullptr, kAstEnd, true};
   }
 
   static Control Try(const byte* pc, int stack_depth, SsaEnv* end_env,
-                     SsaEnv* catch_env, SsaEnv* finish_try_env) {
-    return {pc,      stack_depth, end_env, nullptr, catch_env, finish_try_env,
-            nullptr, kAstEnd,     false};
+                     SsaEnv* catch_env) {
+    return {pc,        stack_depth, end_env, nullptr,
+            catch_env, nullptr,     kAstEnd, false};
   }
 };
 
 // Macros that build nodes only if there is a graph and the current SSA
 // environment is reachable from start. This avoids problems with malformed
 // TF graphs when decoding inputs that have unreachable code.
 #define BUILD(func, ...) (build() ? builder_->func(__VA_ARGS__) : nullptr)
 #define BUILD0(func) (build() ? builder_->func() : nullptr)
 
 // Generic Wasm bytecode decoder with utilities for decoding operands,
@@ skipping 152 matching lines @@
       case kExprI64Const:
       case kExprF64Const:
       case kExprF32Const:
       case kExprGetLocal:
       case kExprGetGlobal:
       case kExprNop:
       case kExprUnreachable:
       case kExprEnd:
       case kExprBlock:
       case kExprThrow:
-      case kExprTryCatch:
-      case kExprTryCatchFinally:
-      case kExprTryFinally:
-      case kExprFinally:
+      case kExprTry:
       case kExprLoop:
         return 0;
 
       case kExprSetGlobal:
       case kExprSetLocal:
       case kExprElse:
       case kExprCatch:
         return 1;
 
       case kExprBr: {
@@ skipping 374 matching lines @@
             SetEnv("block:start", Steal(break_env));
             break;
           }
           case kExprThrow: {
             CHECK_PROTOTYPE_OPCODE(wasm_eh_prototype);
             Pop(0, kAstI32);
 
             // TODO(jpp): start exception propagation.
             break;
           }
-          case kExprTryCatch: {
+          case kExprTry: {
             CHECK_PROTOTYPE_OPCODE(wasm_eh_prototype);
             SsaEnv* outer_env = ssa_env_;
             SsaEnv* try_env = Steal(outer_env);
             SsaEnv* catch_env = Split(try_env);
-            PushTry(outer_env, catch_env, nullptr);
-            SetEnv("try_catch:start", try_env);
-            break;
-          }
-          case kExprTryCatchFinally: {
-            CHECK_PROTOTYPE_OPCODE(wasm_eh_prototype);
-            SsaEnv* outer_env = ssa_env_;
-            SsaEnv* try_env = Steal(outer_env);
-            SsaEnv* catch_env = Split(try_env);
-            SsaEnv* finally_env = Split(try_env);
-            PushTry(finally_env, catch_env, outer_env);
-            SetEnv("try_catch_finally:start", try_env);
-            break;
-          }
-          case kExprTryFinally: {
-            CHECK_PROTOTYPE_OPCODE(wasm_eh_prototype);
-            SsaEnv* outer_env = ssa_env_;
-            SsaEnv* try_env = Steal(outer_env);
-            SsaEnv* finally_env = Split(outer_env);
-            PushTry(finally_env, nullptr, outer_env);
-            SetEnv("try_finally:start", try_env);
+            PushTry(outer_env, catch_env);
+            SetEnv("try:start", try_env);
             break;
           }
           case kExprCatch: {
             CHECK_PROTOTYPE_OPCODE(wasm_eh_prototype);
             LocalIndexOperand operand(this, pc_);
             len = 1 + operand.length;
 
             if (control_.empty()) {
               error(pc_, "catch does not match a any try");
               break;
             }
 
             Control* c = &control_.back();
-            if (!c->has_catch()) {
-              error(pc_, "catch does not match a try with catch");
+            if (!c->is_try()) {
+              error(pc_, "catch does not match a try");
               break;
             }
 
             if (c->catch_env == nullptr) {
               error(pc_, "catch already present for try with catch");
               break;
             }
 
             Goto(ssa_env_, c->end_env);
 
             SsaEnv* catch_env = c->catch_env;
             c->catch_env = nullptr;
             SetEnv("catch:begin", catch_env);
 
             if (Validate(pc_, operand)) {
               // TODO(jpp): figure out how thrown value is propagated. It is
               // unlikely to be a value on the stack.
               if (ssa_env_->locals) {
                 ssa_env_->locals[operand.index] = nullptr;
               }
             }
 
             PopUpTo(c->stack_depth);
 
             break;
           }
-          case kExprFinally: {
-            CHECK_PROTOTYPE_OPCODE(wasm_eh_prototype);
-            if (control_.empty()) {
-              error(pc_, "finally does not match a any try");
-              break;
-            }
-
-            Control* c = &control_.back();
-            if (c->has_catch() && c->catch_env != nullptr) {
-              error(pc_, "missing catch for try with catch and finally");
-              break;
-            }
-
-            if (!c->has_finally()) {
-              error(pc_, "finally does not match a try with finally");
-              break;
-            }
-
-            if (c->finish_try_env == nullptr) {
-              error(pc_, "finally already present for try with finally");
-              break;
-            }
-
-            // ssa_env_ is either the env for either the try or the catch, but
-            // it does not matter: either way we need to direct the control flow
-            // to the end_env, which is the env for the finally.
-            // c->finish_try_env is the the environment enclosing the try block.
-            Goto(ssa_env_, c->end_env);
-
-            PopUpTo(c->stack_depth);
-
-            // The current environment becomes end_env, and finish_try_env
-            // becomes the new end_env. This ensures that any control flow
-            // leaving a try block up to now will do so by branching to the
-            // finally block. Setting the end_env to be finish_try_env ensures
-            // that kExprEnd below can handle the try block as it would any
-            // other block construct.
-            SsaEnv* finally_env = c->end_env;
-            c->end_env = c->finish_try_env;
-            SetEnv("finally:begin", finally_env);
-            c->finish_try_env = nullptr;
-
-            break;
-          }
           case kExprLoop: {
             // The break environment is the outer environment.
             SsaEnv* break_env = ssa_env_;
             PushBlock(break_env);
             SsaEnv* finish_try_env = Steal(break_env);
             // The continue environment is the inner environment.
             PrepareForLoop(pc_, finish_try_env);
             SetEnv("loop:start", Split(finish_try_env));
             ssa_env_->SetNotMerged();
             PushLoop(finish_try_env);
@@ skipping 30 matching lines @@
             }
             Value val = PopUpTo(c->stack_depth);
             MergeInto(c->end_env, &c->node, &c->type, val);
             // Switch to environment for false branch.
             SetEnv("if_else:false", c->false_env);
             c->false_env = nullptr;  // record that an else is already seen
             break;
           }
           case kExprEnd: {
             if (control_.empty()) {
-              error(pc_, "end does not match any if or block");
+              error(pc_, "end does not match any if, try, or block");
               break;
             }
             const char* name = "block:end";
             Control* c = &control_.back();
             Value val = PopUpTo(c->stack_depth);
             if (c->is_loop) {
               // Loops always push control in pairs.
-              control_.pop_back();
+              PopControl();
               c = &control_.back();
               name = "loop:end";
             } else if (c->is_if()) {
               if (c->false_env != nullptr) {
                 // End the true branch of a one-armed if.
                 Goto(c->false_env, c->end_env);
                 val = {val.pc, nullptr, kAstStmt};
                 name = "if:merge";
               } else {
                 // End the false branch of a two-armed if.
                 name = "if_else:merge";
               }
             } else if (c->is_try()) {
               name = "try:end";
 
-              // try blocks do not yield a value.
-              val = {val.pc, nullptr, kAstStmt};
-
-              // validate that catch/finally were seen.
+              // validate that catch was seen.
               if (c->catch_env != nullptr) {
-                error(pc_, "missing catch in try with catch");
-                break;
-              }
-
-              if (c->finish_try_env != nullptr) {
-                error(pc_, "missing finally in try with finally");
+                error(pc_, "missing catch in try");
                 break;
               }
             }
 
             if (ssa_env_->go()) {
+              // Adds a fallthrough edge to the next control block.
               MergeInto(c->end_env, &c->node, &c->type, val);
             }
             SetEnv(name, c->end_env);
             stack_.resize(c->stack_depth);
             Push(c->type, c->node);
-            control_.pop_back();
+            PopControl();
             break;
           }
           case kExprSelect: {
             Value cond = Pop(2, kAstI32);
             Value fval = Pop();
             Value tval = Pop();
             if (tval.type == kAstStmt || tval.type != fval.type) {
               if (tval.type != kAstEnd && fval.type != kAstEnd) {
                 error(pc_, "type mismatch in select");
                 break;
@@ skipping 380 matching lines @@
   void PushLoop(SsaEnv* end_env) {
     const int stack_depth = static_cast<int>(stack_.size());
     control_.emplace_back(Control::Loop(pc_, stack_depth, end_env));
   }
 
   void PushIf(SsaEnv* end_env, SsaEnv* false_env) {
     const int stack_depth = static_cast<int>(stack_.size());
     control_.emplace_back(Control::If(pc_, stack_depth, end_env, false_env));
   }
 
-  void PushTry(SsaEnv* end_env, SsaEnv* catch_env, SsaEnv* finish_try_env) {
+  void PushTry(SsaEnv* end_env, SsaEnv* catch_env) {
     const int stack_depth = static_cast<int>(stack_.size());
-    control_.emplace_back(
-        Control::Try(pc_, stack_depth, end_env, catch_env, finish_try_env));
+    control_.emplace_back(Control::Try(pc_, stack_depth, end_env, catch_env));
   }
 
+  void PopControl() { control_.pop_back(); }
+
   int DecodeLoadMem(LocalType type, MachineType mem_type) {
     MemoryAccessOperand operand(this, pc_,
                                 ElementSizeLog2Of(mem_type.representation()));
 
     Value index = Pop(0, kAstI32);
     TFNode* node = BUILD(LoadMem, type, mem_type, index.node, operand.offset,
                          operand.alignment, position());
     Push(type, node);
     return 1 + operand.length;
   }
@@ skipping 100 matching lines @@
       return val;
     }
   }
 
   int baserel(const byte* ptr) {
     return base_ ? static_cast<int>(ptr - base_) : 0;
   }
 
   int startrel(const byte* ptr) { return static_cast<int>(ptr - start_); }
 
-  void BreakTo(Control* block, Value& val) {
+  void BreakTo(Control* block, const Value& val) {
     if (block->is_loop) {
       // This is the inner loop block, which does not have a value.
       Goto(ssa_env_, block->end_env);
     } else {
       // Merge the value into the production for the block.
       MergeInto(block->end_env, &block->node, &block->type, val);
     }
   }
 
-  void MergeInto(SsaEnv* target, TFNode** node, LocalType* type, Value& val) {
+  void MergeInto(SsaEnv* target, TFNode** node, LocalType* type,
+                 const Value& val) {
     if (!ssa_env_->go()) return;
     DCHECK_NE(kAstEnd, val.type);
 
     bool first = target->state == SsaEnv::kUnreachable;
     Goto(ssa_env_, target);
 
     if (first) {
       // first merge to this environment; set the type and the node.
       *type = val.type;
       *node = val.node;
@@ skipping 224 matching lines @@
         new (zone_) BitVector(static_cast<int>(local_type_vec_.size()), zone_);
     int depth = 0;
     // Iteratively process all AST nodes nested inside the loop.
     while (pc < limit_ && ok()) {
       WasmOpcode opcode = static_cast<WasmOpcode>(*pc);
       unsigned length = 1;
       switch (opcode) {
         case kExprLoop:
         case kExprIf:
         case kExprBlock:
-        case kExprTryCatch:
-        case kExprTryCatchFinally:
-        case kExprTryFinally:
+        case kExprTry:
           depth++;
           DCHECK_EQ(1, OpcodeLength(pc));
           break;
         case kExprSetLocal: {
           LocalIndexOperand operand(this, pc);
           if (assigned->length() > 0 &&
               operand.index < static_cast<uint32_t>(assigned->length())) {
             // Unverified code might have an out-of-bounds index.
             assigned->Add(operand.index);
           }
@@ skipping 150 matching lines @@
 
     for (size_t j = 1; j < length; ++j) {
       os << " " << AsHex(i.pc()[j], 2) << ",";
     }
 
     switch (opcode) {
       case kExprIf:
       case kExprElse:
       case kExprLoop:
       case kExprBlock:
-      case kExprTryCatch:
-      case kExprTryCatchFinally:
-      case kExprTryFinally:
+      case kExprTry:
         os << "   // @" << i.pc_offset();
         control_depth++;
         break;
       case kExprEnd:
         os << "   // @" << i.pc_offset();
         control_depth--;
         break;
       case kExprBr: {
         BreakDepthOperand operand(&i, i.pc());
         os << "   // arity=" << operand.arity << " depth=" << operand.depth;
@@ skipping 55 matching lines @@
 BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
                                            const byte* start, const byte* end) {
   FunctionBody body = {nullptr, nullptr, nullptr, start, end};
   WasmFullDecoder decoder(zone, nullptr, body);
   return decoder.AnalyzeLoopAssignmentForTesting(start, num_locals);
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8