[NFC] Encapsulate source map reader state (#7132)

Move all state relevant to reading source maps out of WasmBinaryReader
and into a new utility, SourceMapReader. This is a prerequisite for
parallelizing the parsing of function bodies, since the source map
reader state is different at the beginning of each function.

Also take the opportunity to simplify the way we read source maps, for
example by deferring the reading of anything but the position of a debug
location until it will be used and by using `std::optional` instead of
singleton `std::set`s to store function prologue and epilogue debug
locations.

1 files changed, 12 insertions, 24 deletions

diff --git a/src/ir/module-utils.cpp b/src/ir/module-utils.cpp
index 5ebd6edef..431e33cc6 100644
--- a/src/ir/module-utils.cpp
+++ b/src/ir/module-utils.cpp
@@ -26,32 +26,20 @@ namespace wasm::ModuleUtils {
 
 // Update the file name indices when moving a set of debug locations from one
 // module to another.
-static void updateLocationSet(std::set<Function::DebugLocation>& locations,
-                              std::vector<Index>& fileIndexMap) {
-  std::set<Function::DebugLocation> updatedLocations;
-
-  for (auto iter : locations) {
-    iter.fileIndex = fileIndexMap[iter.fileIndex];
-    updatedLocations.insert(iter);
+static void updateLocation(std::optional<Function::DebugLocation>& location,
+                           std::vector<Index>& fileIndexMap) {
+  if (location) {
+    location->fileIndex = fileIndexMap[location->fileIndex];
   }
-  locations.clear();
-  std::swap(locations, updatedLocations);
 }
 
 // Update the symbol name indices when moving a set of debug locations from one
 // module to another.
-static void updateSymbolSet(std::set<Function::DebugLocation>& locations,
-                            std::vector<Index>& symbolIndexMap) {
-  std::set<Function::DebugLocation> updatedLocations;
-
-  for (auto iter : locations) {
-    if (iter.symbolNameIndex) {
-      iter.symbolNameIndex = symbolIndexMap[*iter.symbolNameIndex];
-    }
-    updatedLocations.insert(iter);
+static void updateSymbol(std::optional<Function::DebugLocation>& location,
+                         std::vector<Index>& symbolIndexMap) {
+  if (location && location->symbolNameIndex) {
+    location->symbolNameIndex = symbolIndexMap[*location->symbolNameIndex];
   }
-  locations.clear();
-  std::swap(locations, updatedLocations);
 }
 
 // Copies a function into a module. If newName is provided it is used as the
@@ -94,8 +82,8 @@ copyFunctionWithoutAdd(Function* func,
         iter.second->fileIndex = (*fileIndexMap)[iter.second->fileIndex];
       }
     }
-    updateLocationSet(ret->prologLocation, *fileIndexMap);
-    updateLocationSet(ret->epilogLocation, *fileIndexMap);
+    updateLocation(ret->prologLocation, *fileIndexMap);
+    updateLocation(ret->epilogLocation, *fileIndexMap);
   }
   if (symbolNameIndexMap) {
     for (auto& iter : ret->debugLocations) {
@@ -105,8 +93,8 @@ copyFunctionWithoutAdd(Function* func,
             (*symbolNameIndexMap)[*(iter.second->symbolNameIndex)];
         }
       }
-      updateSymbolSet(ret->prologLocation, *symbolNameIndexMap);
-      updateSymbolSet(ret->epilogLocation, *symbolNameIndexMap);
+      updateSymbol(ret->prologLocation, *symbolNameIndexMap);
+      updateSymbol(ret->epilogLocation, *symbolNameIndexMap);
     }
   }
   ret->module = func->module;