[wasm] Add stack checks to loops.

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/zone-containers.h"
@@ skipping 666 matching lines @@
                 ssa_env_->locals[operand.index] = exception_as_i32;
               }
             }
 
             break;
           }
           case kExprLoop: {
             BlockTypeOperand operand(this, pc_);
             SsaEnv* finish_try_env = Steal(ssa_env_);
             // The continue environment is the inner environment.
             PrepareForLoop(pc_, finish_try_env);

[titzer, 2016/10/11 18:44:33]

Can we make PrepareForLoop() return a new environment, the one that should be
used for the loop body?

[ahaas, 2016/10/12 18:03:58]

Done.

-            SetEnv("loop:start", Split(finish_try_env));
+            SetEnv("loop:start", SetLoopStackCheck(Split(finish_try_env)));
             ssa_env_->SetNotMerged();
             PushLoop(finish_try_env);
             SetBlockType(&control_.back(), operand);
             len = 1 + operand.length;
             break;
           }
           case kExprIf: {
             // Condition on top of stack. Split environments for branches.
             BlockTypeOperand operand(this, pc_);
             Value cond = Pop(0, kAstI32);
@@ skipping 933 matching lines @@
       }
     }
 
     // Conservatively introduce phis for all local variables.
     for (int i = EnvironmentCount() - 1; i >= 0; i--) {
       env->locals[i] =
           builder_->Phi(local_type_vec_[i], 1, &env->locals[i], env->control);
     }
   }
 
+  SsaEnv* SetLoopStackCheck(SsaEnv* env) {
+    builder_->StackCheck(position(), &(env->effect), &(env->control));
+    return env;
+  }
+
   // Create a complete copy of the {from}.
   SsaEnv* Split(SsaEnv* from) {
     DCHECK_NOT_NULL(from);
     SsaEnv* result = reinterpret_cast<SsaEnv*>(zone_->New(sizeof(SsaEnv)));
     size_t size = sizeof(TFNode*) * EnvironmentCount();
     result->control = from->control;
     result->effect = from->effect;
 
     if (from->go()) {
       result->state = SsaEnv::kReached;
@@ skipping 284 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