reanalyze: add parallel processing for CMT file analysis

Add support for parallel processing of CMT files during dead code and
exception analysis using OCaml 5 Domains.

Features:
- New -parallel N flag: process files using N domains (0 = sequential)
- -parallel -1: auto-detect number of CPU cores
- New -timing flag: report internal timing breakdown by phase
- New benchmark infrastructure for performance testing

The parallelization targets the CMT file processing phase, which is the
main bottleneck (typically 75-80% of analysis time). The analysis and
reporting phases remain sequential as they require merged cross-file data.

Signed-Off-By: Cursor AI <noreply@cursor.com>

Author: cristianoc

Makefile

@@ -172,6 +172,16 @@ test: lib ninja
 test-analysis: lib ninja
 	make -C tests/analysis_tests clean test
 
+test-reanalyze: lib ninja
+	make -C tests/analysis_tests/tests-reanalyze/deadcode test
+
+test-reanalyze-parallel: lib ninja
+	make -C tests/analysis_tests/tests-reanalyze/deadcode test-parallel
+
+# Benchmark parallel analysis on larger codebase (COPIES=N for more files)
+benchmark-reanalyze: lib ninja
+	make -C tests/analysis_tests/tests-reanalyze/deadcode-benchmark benchmark COPIES=$(or $(COPIES),50)
+
 test-tools: lib ninja
 	make -C tests/tools_tests clean test
 
@@ -244,4 +254,4 @@ dev-container:
 
 .DEFAULT_GOAL := build
 
-.PHONY: yarn-install build ninja rewatch compiler lib artifacts bench test test-analysis test-tools test-syntax test-syntax-roundtrip test-gentype test-rewatch test-all playground playground-compiler playground-test playground-cmijs playground-release format checkformat clean-ninja clean-rewatch clean-compiler clean-lib clean-gentype clean-tests clean dev-container
+.PHONY: yarn-install build ninja rewatch compiler lib artifacts bench test test-analysis test-reanalyze test-reanalyze-parallel benchmark-reanalyze test-tools test-syntax test-syntax-roundtrip test-gentype test-rewatch test-all playground playground-compiler playground-test playground-cmijs playground-release format checkformat clean-ninja clean-rewatch clean-compiler clean-lib clean-gentype clean-tests clean dev-container

analysis/reanalyze/src/Cli.ml

@@ -21,3 +21,9 @@ let excludePaths = ref ([] : string list)
 
 (* test flag: shuffle file order to verify order-independence *)
 let testShuffle = ref false
+
+(* parallel processing: number of domains to use (0 = sequential) *)
+let parallel = ref 0
+
+(* timing: report internal timing of analysis phases *)
+let timing = ref false

analysis/reanalyze/src/DeadValue.ml

@@ -384,9 +384,10 @@ let traverseStructure ~config ~decls ~refs ~file_deps ~cross_file ~file ~doTypes
                   modulePath.path @ [FileContext.module_name_tagged file]
                 in
                 let name = id |> Ident.name |> Name.create in
-                name
-                |> DeadException.add ~config ~decls ~file ~path ~loc
-                     ~strLoc:structureItem.str_loc ~moduleLoc:modulePath.loc;
+                ignore
+                  (DeadException.add ~config ~decls ~file ~path ~loc
+                     ~strLoc:structureItem.str_loc ~moduleLoc:modulePath.loc
+                     name);
                 None
               | _ -> None
             in

analysis/reanalyze/src/Exception.ml

@@ -1,10 +1,10 @@
 open DeadCommon
 
-(** Per-file mutable builder for exception values during AST processing *)
 type values_builder = (Name.t, Exceptions.t) Hashtbl.t
+(** Per-file mutable builder for exception values during AST processing *)
 
-(** Merged immutable table for cross-file lookups *)
 type values_table = (string, (Name.t, Exceptions.t) Hashtbl.t) Hashtbl.t
+(** Merged immutable table for cross-file lookups *)
 
 let create_values_builder () : values_builder = Hashtbl.create 15
 
@@ -174,8 +174,8 @@ module Event = struct
     (exnSet, exnTable)
 end
 
-(** Per-file mutable builder for checks during AST processing *)
 type checks_builder = check list ref
+(** Per-file mutable builder for checks during AST processing *)
 
 and check = {
   events: Event.t list;
@@ -248,8 +248,7 @@ let traverseAst ~file ~values_builder ~checks_builder () =
     | None -> (
       match modulePath with
       | [] -> None
-      | _ :: restModulePath ->
-        path |> findLocalPath ~modulePath:restModulePath)
+      | _ :: restModulePath -> path |> findLocalPath ~modulePath:restModulePath)
   in
   let exceptionsOfPatterns patterns =
     patterns
@@ -537,12 +536,12 @@ let traverseAst ~file ~values_builder ~checks_builder () =
   fun (structure : Typedtree.structure) ->
     process_structure ModulePath.initial structure
 
-(** Result of processing a single file *)
 type file_result = {
   module_name: string;
   values_builder: values_builder;
   checks: check list;
 }
+(** Result of processing a single file *)
 
 let processStructure ~file ~values_builder ~checks_builder
     (structure : Typedtree.structure) =