[wasm] Add a "boolean validation" mode

All instantiations of the function body decoder (validation, Liftoff,
TurboFan) currently generate precise error messages. For Liftoff though,
the error message and location is never used. Thus we can save some
binary size and performance by only keeping a flag whether an error
occured or not. In the error case, the TurboFan compiler will execute
right afterwards anyway, generating a proper error message.

As as follow-up, we can avoid storing the pc in {ValueBase} and
{ControlBase}, because that's only used for error reporting.

R=thibaudm@chromium.org

Bug: v8:10969
Change-Id: I65c46cb9d8b654f9476f2c34ca9a8dd45d6bbbc5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2436347
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70235}

src/wasm/baseline/liftoff-compiler.cc

@@ -258,7 +258,7 @@ class DebugSideTableBuilder {
 class LiftoffCompiler {
  public:
   // TODO(clemensb): Make this a template parameter.
-  static constexpr Decoder::ValidateFlag validate = Decoder::kFullValidation;
+  static constexpr Decoder::ValidateFlag validate = Decoder::kBooleanValidation;
 
   using Value = ValueBase;
 
@@ -4116,7 +4116,7 @@ WasmCompilationResult ExecuteLiftoffCompilation(
   if (debug_sidetable) {
     debug_sidetable_builder = std::make_unique<DebugSideTableBuilder>();
   }
-  WasmFullDecoder<Decoder::kFullValidation, LiftoffCompiler> decoder(
+  WasmFullDecoder<Decoder::kBooleanValidation, LiftoffCompiler> decoder(
       &zone, env->module, env->enabled_features, detected, func_body,
       call_descriptor, env, &zone, instruction_buffer->CreateView(),
       debug_sidetable_builder.get(), for_debugging, func_index, breakpoints,
@@ -4173,7 +4173,7 @@ std::unique_ptr<DebugSideTable> GenerateLiftoffDebugSideTable(
   auto call_descriptor = compiler::GetWasmCallDescriptor(&zone, func_body.sig);
   DebugSideTableBuilder debug_sidetable_builder;
   WasmFeatures detected;
-  WasmFullDecoder<Decoder::kFullValidation, LiftoffCompiler> decoder(
+  WasmFullDecoder<Decoder::kBooleanValidation, LiftoffCompiler> decoder(
       &zone, env->module, env->enabled_features, &detected, func_body,
       call_descriptor, env, &zone,
       NewAssemblerBuffer(AssemblerBase::kDefaultBufferSize),

src/wasm/decoder.h

@@ -40,10 +40,9 @@ using DecodeResult = VoidResult;
 class Decoder {
  public:
   // {ValidateFlag} can be used in a boolean manner ({if (!validate) ...}).
-  // TODO(clemensb): Introduce a "boolean validation" mode where error messages
-  // are locations are not tracked.
   enum ValidateFlag : int8_t {
     kNoValidation = 0,   // Don't run validation, assume valid input.
+    kBooleanValidation,  // Run validation but only store a generic error.
     kFullValidation      // Run full validation with error message and location.
   };
 
@@ -231,6 +230,14 @@ class Decoder {
     return true;
   }
 
+  // Use this for "boolean validation", i.e. if the error message is not used
+  // anyway.
+  void V8_NOINLINE MarkError() {
+    if (!ok()) return;
+    error_ = {0, "validation failed"};
+    onFirstError();
+  }
+
   // Do not inline error methods. This has measurable impact on validation time,
   // see https://crbug.com/910432.
   void V8_NOINLINE error(const char* msg) { errorf(pc_offset(), "%s", msg); }
@@ -241,6 +248,13 @@ class Decoder {
     errorf(offset, "%s", msg);
   }
 
+  void V8_NOINLINE PRINTF_FORMAT(2, 3) errorf(const char* format, ...) {
+    va_list args;
+    va_start(args, format);
+    verrorf(pc_offset(), format, args);
+    va_end(args);
+  }
+
   void V8_NOINLINE PRINTF_FORMAT(3, 4)
       errorf(uint32_t offset, const char* format, ...) {
     va_list args;
@@ -350,7 +364,7 @@ class Decoder {
     onFirstError();
   }
 
-  template <typename IntType, bool validate>
+  template <typename IntType, ValidateFlag validate>
   inline IntType read_little_endian(const byte* pc, const char* msg) {
     if (!validate) {
       DCHECK(validate_size(pc, sizeof(IntType), msg));
@@ -368,7 +382,7 @@ class Decoder {
       pc_ = end_;
       return IntType{0};
     }
-    IntType val = read_little_endian<IntType, false>(pc_, name);
+    IntType val = read_little_endian<IntType, kNoValidation>(pc_, name);
     traceByteRange(pc_, pc_ + sizeof(IntType));
     TRACE("= %d\n", val);
     pc_ += sizeof(IntType);
@@ -418,7 +432,11 @@ class Decoder {
     *length = byte_index + (at_end ? 0 : 1);
     if (validate && V8_UNLIKELY(at_end || (b & 0x80))) {
       TRACE_IF(trace, at_end ? "<end> " : "<length overflow> ");
+      if (validate == kFullValidation) {
         errorf(pc, "expected %s", name);
+      } else {
+        MarkError();
+      }
       result = 0;
     }
     if (is_last_byte) {
@@ -438,7 +456,11 @@ class Decoder {
       if (!validate) {
         DCHECK(valid_extra_bits);
       } else if (V8_UNLIKELY(!valid_extra_bits)) {
+        if (validate == kFullValidation) {
           error(pc, "extra bits in varint");
+        } else {
+          MarkError();
+        }
         result = 0;
       }
     }