[asm.js] Track token positions in scanner.

This adds support for tracking token positions in the asm.js scanner and
uses these positions to emit a mapping from WASM to asm.js positions.
Note that the mapping is still incomplete (some call sites are not yet
covered).

R=clemensh@chromium.org
TEST=debugger/debug/wasm/asm-debug
BUG=v8:6127

Change-Id: Ic8aad1a85e7d9e19da2eec523fcc73d4984afcc8
Reviewed-on: https://chromium-review.googlesource.com/466046
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44335}

src/asmjs/asm-parser.cc

@@ -2000,6 +2000,7 @@ AsmType* AsmJsParser::ParenthesizedExpression() {
 AsmType* AsmJsParser::ValidateCall() {
   AsmType* return_type = call_coercion_;
   call_coercion_ = nullptr;
+  int pos = static_cast<int>(scanner_.Position());
   AsmJsScanner::token_t function_name = Consume();
   int32_t tmp = TempVariable(0);
   if (Check('[')) {
@@ -2113,6 +2114,8 @@ AsmType* AsmJsParser::ValidateCall() {
     } else {
       index = function_info->import->cache_index[cache_index];
     }
+    // TODO(mstarzinger): Fix the {to_number_position} and test it.
+    current_function_builder_->AddAsmWasmOffset(pos, pos);
     current_function_builder_->Emit(kExprCallFunction);
     current_function_builder_->EmitVarUint(index);
   } else if (function_info->type->IsA(AsmType::None())) {
@@ -2127,8 +2130,8 @@ AsmType* AsmJsParser::ValidateCall() {
       current_function_builder_->EmitVarUint(signature_index);
       current_function_builder_->EmitVarUint(0);  // table index
     } else {
-      //      current_function_builder_->AddAsmWasmOffset(scanner_.GetPosition(),
-      //                                                  scanner_.GetPosition());
+      // TODO(mstarzinger): Fix the {to_number_position} and test it.
+      current_function_builder_->AddAsmWasmOffset(pos, pos);
       current_function_builder_->Emit(kExprCallFunction);
       current_function_builder_->EmitDirectCallIndex(function_info->index);
     }

src/asmjs/asm-parser.h

@@ -303,4 +303,5 @@ class AsmJsParser {
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
-#endif
+
+#endif  // V8_ASMJS_ASM_PARSER_H_

src/asmjs/asm-scanner.cc

@@ -22,6 +22,9 @@ AsmJsScanner::AsmJsScanner()
     : token_(kUninitialized),
       preceding_token_(kUninitialized),
       next_token_(kUninitialized),
+      position_(0),
+      preceding_position_(0),
+      next_position_(0),
       rewind_(false),
       in_local_scope_(false),
       global_count_(0),
@@ -49,8 +52,11 @@ void AsmJsScanner::SetStream(std::unique_ptr<Utf16CharacterStream> stream) {
 void AsmJsScanner::Next() {
   if (rewind_) {
     preceding_token_ = token_;
+    preceding_position_ = position_;
     token_ = next_token_;
+    position_ = next_position_;
     next_token_ = kUninitialized;
+    next_position_ = 0;
     rewind_ = false;
     return;
   }
@@ -74,7 +80,10 @@ void AsmJsScanner::Next() {
 
   preceded_by_newline_ = false;
   preceding_token_ = token_;
+  preceding_position_ = position_;
+
   for (;;) {
+    position_ = stream_->pos();
     uc32 ch = stream_->Advance();
     switch (ch) {
       case ' ':
@@ -145,13 +154,17 @@ void AsmJsScanner::Next() {
 }
 
 void AsmJsScanner::Rewind() {
+  DCHECK_NE(kUninitialized, preceding_token_);
   // TODO(bradnelson): Currently rewinding needs to leave in place the
   // preceding newline state (in case a |0 ends a line).
   // This is weird and stateful, fix me.
   DCHECK(!rewind_);
   next_token_ = token_;
+  next_position_ = position_;
   token_ = preceding_token_;
+  position_ = preceding_position_;
   preceding_token_ = kUninitialized;
+  preceding_position_ = 0;
   rewind_ = true;
   identifier_string_.clear();
 }
@@ -207,6 +220,9 @@ void AsmJsScanner::Seek(int pos) {
   preceding_token_ = kUninitialized;
   token_ = kUninitialized;
   next_token_ = kUninitialized;
+  preceding_position_ = 0;
+  position_ = 0;
+  next_position_ = 0;
   rewind_ = false;
   Next();
 }

src/asmjs/asm-scanner.h

@@ -37,6 +37,8 @@ class V8_EXPORT_PRIVATE AsmJsScanner {
 
   // Get current token.
   token_t Token() const { return token_; }
+  // Get position of current token.
+  size_t Position() const { return position_; }
   // Advance to the next token.
   void Next();
   // Back up by one token.
@@ -128,7 +130,10 @@ class V8_EXPORT_PRIVATE AsmJsScanner {
   std::unique_ptr<Utf16CharacterStream> stream_;
   token_t token_;
   token_t preceding_token_;
-  token_t next_token_;
+  token_t next_token_;         // Only set when in {rewind} state.
+  size_t position_;            // Corresponds to {token} position.
+  size_t preceding_position_;  // Corresponds to {preceding_token} position.
+  size_t next_position_;       // Only set when in {rewind} state.
   bool rewind_;
   std::string identifier_string_;
   bool in_local_scope_;
@@ -156,4 +161,5 @@ class V8_EXPORT_PRIVATE AsmJsScanner {
 
 }  // namespace internal
 }  // namespace v8
-#endif
+
+#endif  // V8_ASMJS_ASM_SCANNER_H_

test/debugger/debugger.status

@@ -71,13 +71,6 @@
   'debug/debug-evaluate-locals': [FAIL],
 }],  # variant == turbofan_opt
 
-##############################################################################
-['variant == asm_wasm', {
-  # Issue 6127: We won't fix these in the "old" validator. But we definitely
-  # need to re-enable these for the "new" validator.
-  'debug/wasm/asm-debug': [SKIP],
-}],  # variant == asm_wasm
-
 ##############################################################################
 ['variant == wasm_traps', {
   '*': [SKIP],

test/mjsunit/mjsunit.status

@@ -660,7 +660,6 @@
   # Issue 6127: We won't fix these in the "old" validator. But we definitely
   # need to re-enable these for the "new" validator.
   'regress/regress-618608': [SKIP],
-  'regress/regress-670808': [SKIP],
   'wasm/asm-wasm-exception-in-tonumber': [SKIP],
   'wasm/asm-wasm-stack': [SKIP],
 }],  # variant == asm_wasm