[compiler] Add a stress mode for lazy source positions

If --stress-lazy-source-positions is enabled then always collect source
positions after lazy compilation to try and flush out bytecode mismatch
bugs.

Bug: v8:8510
Change-Id: I895611c9fde2c4743d62951674277973def01d3c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1679502
Commit-Queue: Dan Elphick <delphick@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Auto-Submit: Dan Elphick <delphick@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62414}

src/codegen/compiler.cc

@@ -1346,6 +1346,13 @@ bool Compiler::Compile(Handle<SharedFunctionInfo> shared_info,
   DCHECK(!isolate->has_pending_exception());
   *is_compiled_scope = shared_info->is_compiled_scope();
   DCHECK(is_compiled_scope->is_compiled());
+
+  if (FLAG_stress_lazy_source_positions) {
+    // Collect source positions immediately to try and flush out bytecode
+    // mismatches.
+    SharedFunctionInfo::EnsureSourcePositionsAvailable(isolate, shared_info);
+  }
+
   return true;
 }
 

src/flags/flag-definitions.h

@@ -412,6 +412,8 @@ DEFINE_BOOL(print_bytecode, false,
 DEFINE_BOOL(enable_lazy_source_positions, V8_LAZY_SOURCE_POSITIONS_BOOL,
             "skip generating source positions during initial compile but "
             "regenerate when actually required")
+DEFINE_BOOL(stress_lazy_source_positions, false,
+            "collect lazy source positions immediately after lazy compile")
 DEFINE_STRING(print_bytecode_filter, "*",
               "filter for selecting which functions to print bytecode")
 #ifdef V8_TRACE_IGNITION