Revert "[Torque] Add source positions for Torque files"

This reverts commit 0a24e67a7f.

Reason for revert: Broke Linux 64 UBSan build with unaligned read in the snapshot. Will investigate...

Original change's description:
> [Torque] Add source positions for Torque files
> 
> To improve the Torque debugging experience, we can add source positions
> for each line. This information is carried through the generated
> CSA code (in <output directory>/gen/torque-generated/*.cc) and
> embedded as SourcePositions in the Code object.
> 
> At snapshot time, these SourcePositions are stripped from the Code
> object and turned into platform-appropriate line number debug
> information.
> 
> At this time on Linux, you'll need to build with "is_clang=false"
> in order to use GCC, because crucial steps are missing in Clang's
> ability to convey the information into the binary successfully.
> 
> This CL also introduces a flag to control the existing source
> information in CSA code. --enable-source-at-csa-bind is now set
> to false by default because it's a bit confusing to "hop" between
> source lines in .TQ files and in .CC files. I expect to continue
> making adjustments there, as I want to provide helpful
> debugging aids at the CSA level as well as the Torque level.
> The current configuration prioritizes Torque.
> 
> A detailed guide on usage to follow (also on v8.dev).
> 
> Bug: v8:8418
> Change-Id: Ib4226877ce4cae451bb4d0c546927e89f4e66b58
> Reviewed-on: https://chromium-review.googlesource.com/c/1475473
> Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
> Commit-Queue: Michael Stanton <mvstanton@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59636}

TBR=mvstanton@chromium.org,tebbi@chromium.org

Change-Id: I4ccf94dfdb8b2ba238a60db9ecc8e3ceebef2699
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:8418
Reviewed-on: https://chromium-review.googlesource.com/c/1475757
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59637}

src/compiler/code-assembler.cc

@@ -1762,9 +1762,7 @@ void CodeAssemblerLabel::Bind(AssemblerDebugInfo debug_info) {
         << "\n#    previous: " << *label_->block();
     FATAL("%s", str.str().c_str());
   }
-  if (FLAG_enable_source_at_csa_bind) {
-    state_->raw_assembler_->SetSourcePosition(debug_info.file, debug_info.line);
-  }
+  state_->raw_assembler_->SetSourcePosition(debug_info.file, debug_info.line);
   state_->raw_assembler_->Bind(label_, debug_info);
   UpdateVariablesAfterBind();
 }

src/flag-definitions.h

@@ -850,10 +850,6 @@ DEFINE_STRING(mcpu, "auto", "enable optimization for specific cpu")
 DEFINE_BOOL(partial_constant_pool, true,
             "enable use of partial constant pools (X64 only)")
 
-// Controlling source positions for Torque/CSA code.
-DEFINE_BOOL(enable_source_at_csa_bind, false,
-            "Include source information in the binary at CSA bind locations.")
-
 // Deprecated ARM flags (replaced by arm_arch).
 DEFINE_MAYBE_BOOL(enable_armv7, "deprecated (use --arm_arch instead)")
 DEFINE_MAYBE_BOOL(enable_vfp3, "deprecated (use --arm_arch instead)")

src/torque/csa-generator.cc

@@ -54,20 +54,8 @@ Stack<std::string> CSAGenerator::EmitBlock(const Block* block) {
   return stack;
 }
 
-void CSAGenerator::EmitSourcePosition(SourcePosition pos, bool always_emit) {
-  const std::string& file = SourceFileMap::GetSource(pos.source);
-  if (always_emit || !previous_position_.CompareIgnoreColumn(pos)) {
-    // Lines in Torque SourcePositions are zero-based, while the
-    // CodeStubAssembler and downwind systems are one-based.
-    out_ << "    ca_.SetSourcePosition(\"" << file << "\", " << (pos.line + 1)
-         << ");\n";
-    previous_position_ = pos;
-  }
-}
-
 void CSAGenerator::EmitInstruction(const Instruction& instruction,
                                    Stack<std::string>* stack) {
-  EmitSourcePosition(instruction->pos);
   switch (instruction.kind()) {
 #define ENUM_ITEM(T)          \
   case InstructionKind::k##T: \

src/torque/csa-generator.h

@@ -18,10 +18,7 @@ class CSAGenerator {
  public:
   CSAGenerator(const ControlFlowGraph& cfg, std::ostream& out,
                base::Optional<Builtin::Kind> linkage = base::nullopt)
-      : cfg_(cfg),
-        out_(out),
-        linkage_(linkage),
-        previous_position_(SourcePosition::Invalid()) {}
+      : cfg_(cfg), out_(out), linkage_(linkage) {}
   base::Optional<Stack<std::string>> EmitGraph(Stack<std::string> parameters);
 
   static constexpr const char* ARGUMENTS_VARIABLE_STRING = "arguments";
@@ -34,9 +31,6 @@ class CSAGenerator {
   std::ostream& out_;
   size_t fresh_id_ = 0;
   base::Optional<Builtin::Kind> linkage_;
-  SourcePosition previous_position_;
-
-  void EmitSourcePosition(SourcePosition pos, bool always_emit = false);
 
   std::string PreCallableExceptionPreparation(
       base::Optional<Block*> catch_block);

src/torque/source-positions.h

@@ -14,10 +14,6 @@ namespace internal {
 namespace torque {
 
 class SourceId {
- public:
-  static SourceId Invalid() { return SourceId(-1); }
-  int operator==(const SourceId& s) const { return id_ == s.id_; }
-
  private:
   explicit SourceId(int id) : id_(id) {}
   int id_;
@@ -28,17 +24,6 @@ struct SourcePosition {
   SourceId source;
   int line;
   int column;
-  static SourcePosition Invalid() {
-    SourcePosition pos{SourceId::Invalid(), -1, -1};
-    return pos;
-  }
-  int operator==(const SourcePosition& pos) const {
-    return line == pos.line && column == pos.column && source == pos.source;
-  }
-  int operator!=(const SourcePosition& pos) const { return !(*this == pos); }
-  bool CompareIgnoreColumn(const SourcePosition& pos) const {
-    return line == pos.line && source == pos.source;
-  }
 };
 
 DECLARE_CONTEXTUAL_VARIABLE(CurrentSourceFile, SourceId);