From 13ec76dfbc1c72a5e77d6a33fca5bf349308162d Mon Sep 17 00:00:00 2001
From: Alon Zakai <alonzakai@gmail.com>
Date: Tue, 21 Nov 2017 17:08:28 -0800
Subject: Fix reading breaks to the function exit (#1304)

* remove unneeded code to handle a br to the return from the function. Now that we use getBlockOrSingleton there, it does that for us anyhow
---
 src/wasm-binary.h        |  1 -
 src/wasm/wasm-binary.cpp | 22 +++++-----------------
 2 files changed, 5 insertions(+), 18 deletions(-)

(limited to 'src')

diff --git a/src/wasm-binary.h b/src/wasm-binary.h
index 068f59d62..a407c56e4 100644
--- a/src/wasm-binary.h
+++ b/src/wasm-binary.h
@@ -864,7 +864,6 @@ public:
   };
   std::vector<BreakTarget> breakStack;
   std::unordered_set<Name> breakTargetNames;
-  bool breaksToReturn; // whether a break is done to the function scope, which is in effect a return
 
   std::vector<Expression*> expressionStack;
 
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index b5bce8649..2d1e8734c 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -1204,8 +1204,6 @@ void WasmBinaryWriter::visitDrop(Drop *curr) {
 
 // reader
 
-static Name RETURN_BREAK("binaryen|break-to-return");
-
 void WasmBinaryBuilder::read() {
 
   readHeader();
@@ -1626,17 +1624,14 @@ void WasmBinaryBuilder::readFunctions() {
       if (debug) std::cerr << "processing function: " << i << std::endl;
       nextLabel = 0;
       useDebugLocation = false;
-      breaksToReturn = false;
       // process body
       assert(breakTargetNames.size() == 0);
       assert(breakStack.empty());
-      breakStack.emplace_back(RETURN_BREAK, func->result != none); // the break target for the function scope
       assert(expressionStack.empty());
       assert(depth == 0);
       func->body = getBlockOrSingleton(func->result);
       assert(depth == 0);
-      assert(breakStack.size() == 1);
-      breakStack.pop_back();
+      assert(breakStack.size() == 0);
       assert(breakTargetNames.size() == 0);
       if (!expressionStack.empty()) {
         throw ParseException("stack not empty on function exit");
@@ -1644,10 +1639,6 @@ void WasmBinaryBuilder::readFunctions() {
       if (pos != endOfFunction) {
         throw ParseException("binary offset at function exit not at expected location");
       }
-      if (breaksToReturn) {
-        // we broke to return, so we need an outer block to break to
-        func->body = Builder(wasm).blockifyWithName(func->body, RETURN_BREAK);
-      }
     }
     currFunction = nullptr;
     functions.push_back(func);
@@ -2325,15 +2316,12 @@ void WasmBinaryBuilder::visitLoop(Loop *curr) {
 
 WasmBinaryBuilder::BreakTarget WasmBinaryBuilder::getBreakTarget(int32_t offset) {
   if (debug) std::cerr << "getBreakTarget " << offset << std::endl;
+  if (breakStack.size() < 1 + size_t(offset)) {
+    throw ParseException("bad breakindex (low)");
+  }
   size_t index = breakStack.size() - 1 - offset;
   if (index >= breakStack.size()) {
-    throw ParseException("bad breakindex");
-  }
-  if (index == 0) {
-    // trying to access the topmost element means we break out
-    // to the function scope, doing in effect a return, we'll
-    // need to create a block for that.
-    breaksToReturn = true;
+    throw ParseException("bad breakindex (high)");
   }
   if (debug) std::cerr << "breaktarget "<< breakStack[index].name << " arity " << breakStack[index].arity <<  std::endl;
   auto& ret = breakStack[index];
-- 
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