[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.

2 files changed, 13 insertions, 25 deletions

diff --git a/test/gtest/CMakeLists.txt b/test/gtest/CMakeLists.txt
index c3d281f1c..102d3ca2a 100644
--- a/test/gtest/CMakeLists.txt
+++ b/test/gtest/CMakeLists.txt
@@ -3,7 +3,7 @@ include_directories(../../src/wasm)
 
 set(unittest_SOURCES
   arena.cpp
-  binary-reader.cpp
+  source-map.cpp
   cfg.cpp
   dfa_minimization.cpp
   disjoint_sets.cpp
diff --git a/test/gtest/binary-reader.cpp b/test/gtest/source-map.cpp
index b73fe55bd..c943be172 100644
--- a/test/gtest/binary-reader.cpp
+++ b/test/gtest/source-map.cpp
@@ -14,24 +14,19 @@
  * limitations under the License.
  */
 
-#include "parser/wat-parser.h"
+#include "source-map.h"
 #include "print-test.h"
-#include "wasm-binary.h"
 #include "gtest/gtest.h"
 
 using namespace wasm;
 
-using BinaryReaderTest = PrintTest;
+using SourceMapTest = PrintTest;
 
 // Check that debug location parsers can handle single-segment mappings.
-TEST_F(BinaryReaderTest, SourceMappingSingleSegment) {
-  auto moduleText = "(module)";
-  Module module;
-  parseWast(module, moduleText);
-
-  BufferWithRandomAccess buffer;
-  WasmBinaryWriter(&module, buffer, PassOptions());
-  auto moduleBytes = buffer.getAsChars();
+TEST_F(SourceMapTest, SourceMappingSingleSegment) {
+  auto text = "(module)";
+  Module wasm;
+  parseWast(wasm, text);
 
   // A single-segment mapping starting at offset 0.
   std::string sourceMap = R"(
@@ -42,22 +37,15 @@ TEST_F(BinaryReaderTest, SourceMappingSingleSegment) {
           "mappings": "A"
       }
   )";
-  std::stringstream sourceMapStream(sourceMap);
+  std::vector<char> buffer(sourceMap.begin(), sourceMap.end());
+
+  SourceMapReader reader(buffer);
 
   // Test `readSourceMapHeader` (only check for errors, as there is no mapping
   // to print).
-  {
-    Module module;
-    WasmBinaryReader binaryReader(module, FeatureSet::All, moduleBytes);
-    binaryReader.setDebugLocations(&sourceMapStream);
-    binaryReader.readSourceMapHeader();
-  }
+  reader.readHeader(wasm);
 
   // Test `readNextDebugLocation`.
-  {
-    Module module;
-    WasmBinaryReader binaryReader(module, FeatureSet::All, moduleBytes);
-    binaryReader.setDebugLocations(&sourceMapStream);
-    binaryReader.readNextDebugLocation();
-  }
+  // TODO: Actually check the result.
+  reader.readDebugLocationAt(1);
 }