[wasm] Make trace flags read only in release builds

This saves us 14.2kB binary size in libv8.so (in release mode), and
probably also improves performance a little bit.

R=titzer@chromium.org

Bug: v8:7109
Change-Id: I345a48369aaf054572a4fd4368bf5cd526ed146a
Reviewed-on: https://chromium-review.googlesource.com/797270
Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49905}

src/flag-definitions.h

@@ -26,7 +26,7 @@
 #define FLAG_FULL(ftype, ctype, nam, def, cmt) \
   V8_EXPORT_PRIVATE extern ctype FLAG_##nam;
 #define FLAG_READONLY(ftype, ctype, nam, def, cmt) \
-  static ctype const FLAG_##nam = def;
+  static constexpr ctype FLAG_##nam = def;
 
 // We want to supply the actual storage and value for the flag variable in the
 // .cc file.  We only do this for writable flags.
@@ -44,7 +44,7 @@
 // for MODE_META, so there is no impact on the flags interface.
 #elif defined(FLAG_MODE_DEFINE_DEFAULTS)
 #define FLAG_FULL(ftype, ctype, nam, def, cmt) \
-  static ctype const FLAGDEFAULT_##nam = def;
+  static constexpr ctype FLAGDEFAULT_##nam = def;
 
 // We want to write entries into our meta data table, for internal parsing and
 // printing / etc in the flag parser code.  We only do this for writable flags.
@@ -172,6 +172,12 @@ struct MaybeBoolFlag {
   FLAG_ALIAS(STRING, const char*, alias, nam)
 #define DEFINE_ALIAS_ARGS(alias, nam) FLAG_ALIAS(ARGS, JSArguments, alias, nam)
 
+#ifdef DEBUG
+#define DEFINE_DEBUG_BOOL DEFINE_BOOL
+#else
+#define DEFINE_DEBUG_BOOL DEFINE_BOOL_READONLY
+#endif
+
 //
 // Flags in all modes.
 //
@@ -473,7 +479,8 @@ DEFINE_BOOL(wasm_disable_structured_cloning, false,
             "disable wasm structured cloning")
 DEFINE_INT(wasm_num_compilation_tasks, 10,
            "number of parallel compilation tasks for wasm")
-DEFINE_BOOL(wasm_trace_native_heap, false, "trace wasm native heap events")
+DEFINE_DEBUG_BOOL(wasm_trace_native_heap, false,
+                  "trace wasm native heap events")
 DEFINE_BOOL(wasm_jit_to_native, false,
             "JIT wasm code to native (not JS GC) memory")
 DEFINE_BOOL(wasm_trace_serialization, false,
@@ -492,21 +499,24 @@ DEFINE_UINT(wasm_max_mem_pages, v8::internal::wasm::kV8MaxWasmMemoryPages,
             "maximum memory size of a wasm instance")
 DEFINE_UINT(wasm_max_table_size, v8::internal::wasm::kV8MaxWasmTableSize,
             "maximum table size of a wasm instance")
-DEFINE_BOOL(trace_wasm_decoder, false, "trace decoding of wasm code")
-DEFINE_BOOL(trace_wasm_decode_time, false, "trace decoding time of wasm code")
-DEFINE_BOOL(trace_wasm_compiler, false, "trace compiling of wasm code")
-DEFINE_BOOL(trace_wasm_interpreter, false, "trace interpretation of wasm code")
-DEFINE_BOOL(trace_wasm_streaming, false,
-            "trace streaming compilation of wasm code")
+DEFINE_DEBUG_BOOL(trace_wasm_decoder, false, "trace decoding of wasm code")
+DEFINE_DEBUG_BOOL(trace_wasm_decode_time, false,
+                  "trace decoding time of wasm code")
+DEFINE_DEBUG_BOOL(trace_wasm_compiler, false, "trace compiling of wasm code")
+DEFINE_DEBUG_BOOL(trace_wasm_interpreter, false,
+                  "trace interpretation of wasm code")
+DEFINE_DEBUG_BOOL(trace_wasm_streaming, false,
+                  "trace streaming compilation of wasm code")
 DEFINE_INT(trace_wasm_ast_start, 0,
            "start function for wasm AST trace (inclusive)")
 DEFINE_INT(trace_wasm_ast_end, 0, "end function for wasm AST trace (exclusive)")
 DEFINE_BOOL(liftoff, false,
             "enable liftoff, the experimental wasm baseline compiler")
-DEFINE_BOOL(trace_liftoff, false, "trace liftoff, the wasm baseline compiler")
+DEFINE_DEBUG_BOOL(trace_liftoff, false,
+                  "trace liftoff, the wasm baseline compiler")
 DEFINE_UINT(skip_compiling_wasm_funcs, 0, "start compiling at function N")
-DEFINE_BOOL(wasm_break_on_decoder_error, false,
-            "debug break when wasm decoder encounters an error")
+DEFINE_DEBUG_BOOL(wasm_break_on_decoder_error, false,
+                  "debug break when wasm decoder encounters an error")
 DEFINE_BOOL(wasm_trace_memory, false,
             "print all memory updates performed in wasm code")
 
@@ -519,7 +529,7 @@ DEFINE_BOOL(trace_asm_scanner, false,
 DEFINE_BOOL(trace_asm_parser, false, "verbose logging of asm.js parse failures")
 DEFINE_BOOL(stress_validate_asm, false, "try to validate everything as asm.js")
 
-DEFINE_BOOL(dump_wasm_module, false, "dump wasm module bytes")
+DEFINE_DEBUG_BOOL(dump_wasm_module, false, "dump wasm module bytes")
 DEFINE_STRING(dump_wasm_module_path, nullptr,
               "directory to dump wasm modules to")
 
@@ -551,8 +561,8 @@ DEFINE_BOOL(asm_wasm_lazy_compilation, false,
 DEFINE_IMPLICATION(validate_asm, asm_wasm_lazy_compilation)
 DEFINE_BOOL(wasm_lazy_compilation, false,
             "enable lazy compilation for all wasm modules")
-DEFINE_BOOL(trace_wasm_lazy_compilation, false,
-            "trace lazy compilation of wasm functions")
+DEFINE_DEBUG_BOOL(trace_wasm_lazy_compilation, false,
+                  "trace lazy compilation of wasm functions")
 // wasm-interpret-all resets {asm-,}wasm-lazy-compilation.
 DEFINE_NEG_IMPLICATION(wasm_interpret_all, asm_wasm_lazy_compilation)
 DEFINE_NEG_IMPLICATION(wasm_interpret_all, wasm_lazy_compilation)
@@ -1081,8 +1091,8 @@ DEFINE_BOOL(trace_regexp_parser, false, "trace regexp parsing")
 DEFINE_BOOL(print_break_location, false, "print source location on debug break")
 
 // wasm instance management
-DEFINE_BOOL(trace_wasm_instances, false,
-            "trace creation and collection of wasm instances")
+DEFINE_DEBUG_BOOL(trace_wasm_instances, false,
+                  "trace creation and collection of wasm instances")
 
 //
 // Logging and profiling flags
@@ -1285,6 +1295,7 @@ DEFINE_IMPLICATION(unbox_double_fields, track_double_fields)
 
 #undef DEFINE_BOOL
 #undef DEFINE_MAYBE_BOOL
+#undef DEFINE_DEBUG_BOOL
 #undef DEFINE_INT
 #undef DEFINE_STRING
 #undef DEFINE_FLOAT

src/wasm/decoder.h

@@ -19,7 +19,6 @@ namespace v8 {
 namespace internal {
 namespace wasm {
 
-#if DEBUG
 #define TRACE(...)                                    \
   do {                                                \
     if (FLAG_trace_wasm_decoder) PrintF(__VA_ARGS__); \
@@ -28,10 +27,6 @@ namespace wasm {
   do {                                                          \
     if (FLAG_trace_wasm_decoder && (cond)) PrintF(__VA_ARGS__); \
   } while (false)
-#else
-#define TRACE(...)
-#define TRACE_IF(...)
-#endif
 
 // A {DecodeResult} only stores the failure / success status, but no data. Thus
 // we use {nullptr_t} as data value, such that the only valid data stored in

src/wasm/function-body-decoder-impl.h

@@ -22,14 +22,10 @@ namespace wasm {
 struct WasmGlobal;
 struct WasmException;
 
-#if DEBUG
 #define TRACE(...)                                    \
   do {                                                \
     if (FLAG_trace_wasm_decoder) PrintF(__VA_ARGS__); \
   } while (false)
-#else
-#define TRACE(...)
-#endif
 
 // Return the evaluation of `condition` if validate==true, DCHECK that it's
 // true and always return true otherwise.

src/wasm/module-decoder.cc

@@ -21,14 +21,11 @@ namespace v8 {
 namespace internal {
 namespace wasm {
 
-#if DEBUG
 #define TRACE(...)                                    \
   do {                                                \
     if (FLAG_trace_wasm_decoder) PrintF(__VA_ARGS__); \
   } while (false)
-#else
-#define TRACE(...)
-#endif
+
 namespace {
 
 constexpr char kNameString[] = "name";

src/wasm/wasm-interpreter.cc

@@ -32,14 +32,10 @@ namespace v8 {
 namespace internal {
 namespace wasm {
 
-#if DEBUG
 #define TRACE(...)                                        \
   do {                                                    \
     if (FLAG_trace_wasm_interpreter) PrintF(__VA_ARGS__); \
   } while (false)
-#else
-#define TRACE(...)
-#endif
 
 #define FOREACH_INTERNAL_OPCODE(V) V(Breakpoint, 0xFF)
 

src/wasm/wasm-module.cc

@@ -31,21 +31,6 @@ namespace v8 {
 namespace internal {
 namespace wasm {
 
-#define TRACE(...)                                      \
-  do {                                                  \
-    if (FLAG_trace_wasm_instances) PrintF(__VA_ARGS__); \
-  } while (false)
-
-#define TRACE_CHAIN(instance)        \
-  do {                               \
-    instance->PrintInstancesChain(); \
-  } while (false)
-
-#define TRACE_COMPILE(...)                             \
-  do {                                                 \
-    if (FLAG_trace_wasm_compiler) PrintF(__VA_ARGS__); \
-  } while (false)
-
 // static
 const WasmExceptionSig WasmException::empty_sig_(0, 0, nullptr);
 
@@ -449,10 +434,6 @@ const char* ExternalKindName(WasmExternalKind kind) {
   return "unknown";
 }
 
-#undef TRACE
-#undef TRACE_CHAIN
-#undef TRACE_COMPILE
-
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8

test/cctest/wasm/wasm-run-utils.cc

@@ -274,11 +274,13 @@ void TestBuildingGraph(
   DecodeResult result =
       BuildTFGraph(zone->allocator(), &builder, sig, start, end);
   if (result.failed()) {
+#ifdef DEBUG
     if (!FLAG_trace_wasm_decoder) {
       // Retry the compilation with the tracing flag on, to help in debugging.
       FLAG_trace_wasm_decoder = true;
       result = BuildTFGraph(zone->allocator(), &builder, sig, start, end);
     }
+#endif
 
     uint32_t pc = result.error_offset();
     std::ostringstream str;