[wasm] Add stack checks to loops.

src/wasm/ast-decoder.cc

Index: src/wasm/ast-decoder.cc
diff --git a/src/wasm/ast-decoder.cc b/src/wasm/ast-decoder.cc
index 025ccdf1d7bfc0d2c159e511600b0d313cf0fa9b..b47ab82ec122fc46d092eecc96e6fdb6db9ccf6e 100644
--- a/src/wasm/ast-decoder.cc
+++ b/src/wasm/ast-decoder.cc
@@ -685,7 +685,7 @@ class WasmFullDecoder : public WasmDecoder {
             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);
@@ -1639,6 +1639,11 @@ class WasmFullDecoder : public WasmDecoder {
     }
   }
 
+  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);