[code-assembler] Make phi creation deterministic

Phi creation in the code assembler was dependent on the addresses
of the CodeAssemblerVariable::Impl object. This caused non-determinism
in mksnapshot which sometimes occurred on Windows.

This CL adds IDs to CodeAssemblerVariable::Impl objects and ensures
all iterations are done in ID order instead of object address order.


Change-Id: I2b370dc5153202be864a5c13289e70f5ebd59e2e
Bug: v8:8391
Reviewed-on: https://chromium-review.googlesource.com/c/1319749
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57276}

src/compiler/code-assembler.cc

@@ -1545,13 +1545,14 @@ RawMachineAssembler* CodeAssembler::raw_assembler() const {
 // properly be verified.
 class CodeAssemblerVariable::Impl : public ZoneObject {
  public:
-  explicit Impl(MachineRepresentation rep)
+  explicit Impl(MachineRepresentation rep, CodeAssemblerState::VariableId id)
       :
 #if DEBUG
         debug_info_(AssemblerDebugInfo(nullptr, nullptr, -1)),
 #endif
         value_(nullptr),
-        rep_(rep) {
+        rep_(rep),
+        var_id_(id) {
   }
 
 #if DEBUG
@@ -1562,13 +1563,25 @@ class CodeAssemblerVariable::Impl : public ZoneObject {
 
   AssemblerDebugInfo debug_info_;
 #endif  // DEBUG
+  bool operator<(const CodeAssemblerVariable::Impl& other) const {
+    return var_id_ < other.var_id_;
+  }
   Node* value_;
   MachineRepresentation rep_;
+  CodeAssemblerState::VariableId var_id_;
 };
 
+bool CodeAssemblerVariable::ImplComparator::operator()(
+    const CodeAssemblerVariable::Impl* a,
+    const CodeAssemblerVariable::Impl* b) const {
+  return *a < *b;
+}
+
 CodeAssemblerVariable::CodeAssemblerVariable(CodeAssembler* assembler,
                                              MachineRepresentation rep)
-    : impl_(new (assembler->zone()) Impl(rep)), state_(assembler->state()) {
+    : impl_(new (assembler->zone())
+                Impl(rep, assembler->state()->NextVariableId())),
+      state_(assembler->state()) {
   state_->variables_.insert(impl_);
 }
 
@@ -1583,7 +1596,9 @@ CodeAssemblerVariable::CodeAssemblerVariable(CodeAssembler* assembler,
 CodeAssemblerVariable::CodeAssemblerVariable(CodeAssembler* assembler,
                                              AssemblerDebugInfo debug_info,
                                              MachineRepresentation rep)
-    : impl_(new (assembler->zone()) Impl(rep)), state_(assembler->state()) {
+    : impl_(new (assembler->zone())
+                Impl(rep, assembler->state()->NextVariableId())),
+      state_(assembler->state()) {
   impl_->set_debug_info(debug_info);
   state_->variables_.insert(impl_);
 }

src/compiler/code-assembler.h

@@ -1389,6 +1389,10 @@ class CodeAssemblerVariable {
   friend class CodeAssemblerState;
   friend std::ostream& operator<<(std::ostream&, const Impl&);
   friend std::ostream& operator<<(std::ostream&, const CodeAssemblerVariable&);
+  struct ImplComparator {
+    bool operator()(const CodeAssemblerVariable::Impl* a,
+                    const CodeAssemblerVariable::Impl* b) const;
+  };
   Impl* impl_;
   CodeAssemblerState* state_;
   DISALLOW_COPY_AND_ASSIGN(CodeAssemblerVariable);
@@ -1478,10 +1482,14 @@ class CodeAssemblerLabel {
   RawMachineLabel* label_;
   // Map of variables that need to be merged to their phi nodes (or placeholders
   // for those phis).
-  std::map<CodeAssemblerVariable::Impl*, Node*> variable_phis_;
+  std::map<CodeAssemblerVariable::Impl*, Node*,
+           CodeAssemblerVariable::ImplComparator>
+      variable_phis_;
   // Map of variables to the list of value nodes that have been added from each
   // merge path in their order of merging.
-  std::map<CodeAssemblerVariable::Impl*, std::vector<Node*>> variable_merges_;
+  std::map<CodeAssemblerVariable::Impl*, std::vector<Node*>,
+           CodeAssemblerVariable::ImplComparator>
+      variable_merges_;
 };
 
 class CodeAssemblerParameterizedLabelBase {
@@ -1592,10 +1600,14 @@ class V8_EXPORT_PRIVATE CodeAssemblerState {
   uint32_t stub_key_;
   int32_t builtin_index_;
   bool code_generated_;
-  ZoneSet<CodeAssemblerVariable::Impl*> variables_;
+  ZoneSet<CodeAssemblerVariable::Impl*, CodeAssemblerVariable::ImplComparator>
+      variables_;
   CodeAssemblerCallback call_prologue_;
   CodeAssemblerCallback call_epilogue_;
   std::vector<CodeAssemblerExceptionHandlerLabel*> exception_handler_labels_;
+  typedef uint32_t VariableId;
+  VariableId next_variable_id_ = 0;
+  VariableId NextVariableId() { return next_variable_id_++; }
 
   DISALLOW_COPY_AND_ASSIGN(CodeAssemblerState);
 };