1 files changed, 34 insertions, 0 deletions
diff --git a/src/wasm.h b/src/wasm.h
index 8b60885e3..f30a24d6b 100644
--- a/src/wasm.h
+++ b/src/wasm.h
@@ -1172,7 +1172,39 @@ struct BinaryLocations {
   struct Span {
     BinaryLocation start = 0, end = 0;
   };
+
+  // Track the range of addresses an expressions appears at. This is the
+  // contiguous range that all instructions have - control flow instructions
+  // have additional opcodes later (like an end for a block or loop), see
+  // just after this.
   std::unordered_map<Expression*, Span> expressions;
+
+  // Track the extra delimiter positions that some instructions, in particular
+  // control flow, have, like 'end' for loop and block. We keep these in a
+  // separate map because they are rare and we optimize for the storage space
+  // for the common type of instruction which just needs a Span. We implement
+  // this as a simple struct with two elements (as two extra elements is the
+  // maximum currently needed; due to 'catch' and 'end' for try-catch). The
+  // second value may be 0, indicating it is not used.
+  struct DelimiterLocations : public std::array<BinaryLocation, 2> {
+    DelimiterLocations() {
+      // Ensure zero-initialization.
+      for (auto& item : *this) {
+        item = 0;
+      }
+    }
+  };
+
+  enum DelimiterId {
+    // All control flow structures have an end, so use index 0 for that.
+    End = 0,
+    // Use index 1 for all other current things.
+    Else = 1,
+    Catch = 1,
+    Invalid = -1
+  };
+  std::unordered_map<Expression*, DelimiterLocations> delimiters;
+
   std::unordered_map<Function*, Span> functions;
 };
 
@@ -1231,6 +1263,8 @@ public:
 
   // General debugging info support: track instructions and the function itself.
   std::unordered_map<Expression*, BinaryLocations::Span> expressionLocations;
+  std::unordered_map<Expression*, BinaryLocations::DelimiterLocations>
+    delimiterLocations;
   BinaryLocations::Span funcLocation;
 
   size_t getNumParams();