[Parser] Propagate debug locations like the old parser

src/parser/wat-parser.cpp

@@ -19,6 +19,7 @@
 #include "ir/names.h"
 #include "lexer.h"
 #include "parsers.h"
+#include "pass.h"
 #include "wasm-type.h"
 #include "wasm.h"
 
@@ -90,6 +91,58 @@ Result<> parseDefs(Ctx& ctx,
   return Ok{};
 }
 
+void propagateDebugLocations(Module& wasm) {
+  // Copy debug locations from parents or previous siblings to expressions that
+  // do not already have their own debug locations.
+  struct Propagator : WalkerPass<ExpressionStackWalker<Propagator>> {
+    using Super = WalkerPass<ExpressionStackWalker<Propagator>>;
+    bool isFunctionParallel() override { return true; }
+    bool modifiesBinaryenIR() override { return false; }
+    bool requiresNonNullableLocalFixups() override { return false; }
+    void runOnFunction(Module* module, Function* func) override {
+      if (!func->debugLocations.empty()) {
+        Super::runOnFunction(module, func);
+      }
+    }
+
+    // Unannotated instructions inherit either their previous sibling's location
+    // or their parent's location. Look up whichever is current for a given
+    // parent.
+    std::unordered_map<Expression*, Function::DebugLocation> parentDefaults;
+
+    static void doPreVisit(Propagator* self, Expression** currp) {
+      Super::doPreVisit(self, currp);
+      auto* curr = *currp;
+      auto& locs = self->getFunction()->debugLocations;
+      auto& parentDefaults = self->parentDefaults;
+      if (auto it = locs.find(curr); it != locs.end()) {
+        // Children will inherit this location.
+        parentDefaults[curr] = it->second;
+        if (auto* parent = self->getParent()) {
+          // Subsequent siblings will inherit this location.
+          parentDefaults[parent] = it->second;
+        }
+      } else {
+        // No annotation, see if we should inherit one.
+        if (auto* parent = self->getParent()) {
+          if (auto defaultIt = parentDefaults.find(parent);
+              defaultIt != parentDefaults.end()) {
+            // We have a default to inherit. Our children will inherit it, too.
+            locs[curr] = parentDefaults[curr] = defaultIt->second;
+          }
+        }
+      }
+    }
+
+    std::unique_ptr<Pass> create() override {
+      return std::make_unique<Propagator>();
+    }
+  };
+  PassRunner runner(&wasm);
+  runner.add(std::make_unique<Propagator>());
+  runner.run();
+}
+
 // ================
 // Parser Functions
 // ================
@@ -212,6 +265,8 @@ Result<> parseModule(Module& wasm, std::string_view input) {
     }
   }
 
+  propagateDebugLocations(wasm);
+
   return Ok{};
 }
 

test/lit/wat-kitchen-sink.wast

@@ -5192,6 +5192,32 @@
   end
  )
 
+ ;; CHECK:      (func $source-map-propagation (type $void)
+ ;; CHECK-NEXT:  ;;@ src.cpp:20:1
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (i32.add
+ ;; CHECK-NEXT:    ;;@ src.cpp:10:1
+ ;; CHECK-NEXT:    (i32.const 0)
+ ;; CHECK-NEXT:    ;;@ src.cpp:10:1
+ ;; CHECK-NEXT:    (i32.const 1)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT:  ;;@ src.cpp:20:1
+ ;; CHECK-NEXT:  (drop
+ ;; CHECK-NEXT:   (i32.const 2)
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $source-map-propagation
+  ;;@ src.cpp:10:1
+  i32.const 0
+  i32.const 1
+  i32.add
+  ;;@ src.cpp:20:1
+  drop
+  i32.const 2
+  drop
+ )
+
  ;; CHECK:      (func $use-types (type $104) (param $0 (ref $s0)) (param $1 (ref $s1)) (param $2 (ref $s2)) (param $3 (ref $s3)) (param $4 (ref $s4)) (param $5 (ref $s5)) (param $6 (ref $s6)) (param $7 (ref $s7)) (param $8 (ref $s8)) (param $9 (ref $a0)) (param $10 (ref $a1)) (param $11 (ref $a2)) (param $12 (ref $a3)) (param $13 (ref $subvoid)) (param $14 (ref $submany)) (param $15 (ref $all-types))
  ;; CHECK-NEXT:  (nop)
  ;; CHECK-NEXT: )