PostfixExpression: move parser out of NativePDB internals

Summary:
The postfix expressions in PDB and breakpad symbol files are similar
enough that they can be parsed by the same parser. This patch
generalizes the parser in the NativePDB plugin and moves it into the
PostfixExpression file created in the previous commit (r358976).

The generalization consists of treating any unrecognised token as a
"symbol" node (previously these would only be created for tokens
starting with "$", and other token would abort the parse). This is
needed because breakpad symbols can also contain ".cfa" tokens, which
refer to the frame's CFA.

The cosmetic changes include:
- using a factory function instead of a class for creating nodes (this
  is more generic as it allows the same BumpPtrAllocator to be used for
  other things too)
- using dedicated function for parsing operator tokens instead of a
  DenseMap (more efficient as we don't need to create the DenseMap every
  time).

Reviewers: amccarth, clayborg, JDevlieghere, aleksandr.urakov

Subscribers: jasonmolenda, lldb-commits, markmentovai, mgorny

Differential Revision: https://reviews.llvm.org/D61003

llvm-svn: 359073

lldb/include/lldb/Symbol/PostfixExpression.h

@@ -15,6 +15,7 @@
 #define LLDB_SYMBOL_POSTFIXEXPRESSION_H
 
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Allocator.h"
 #include "llvm/Support/Casting.h"
 
 namespace lldb_private {
@@ -173,6 +174,17 @@ protected:
   }
 };
 
+template <typename T, typename... Args>
+inline T *MakeNode(llvm::BumpPtrAllocator &alloc, Args &&... args) {
+  static_assert(std::is_trivially_destructible<T>::value,
+                "This object will not be destroyed!");
+  return new (alloc.Allocate<T>()) T(std::forward<Args>(args)...);
+}
+
+/// Parse the given postfix expression. The parsed nodes are placed into the
+/// provided allocator.
+Node *Parse(llvm::StringRef expr, llvm::BumpPtrAllocator &alloc);
+
 } // namespace postfix
 } // namespace lldb_private
 

lldb/source/Plugins/SymbolFile/NativePDB/PdbFPOProgramToDWARFExpression.cpp

@@ -26,19 +26,6 @@ using namespace lldb_private::postfix;
 
 namespace {
 
-class NodeAllocator {
-public:
-  template <typename T, typename... Args> T *makeNode(Args &&... args) {
-    static_assert(std::is_trivially_destructible<T>::value,
-                  "This object will not be destroyed!");
-    void *new_node_mem = m_alloc.Allocate(sizeof(T), alignof(T));
-    return new (new_node_mem) T(std::forward<Args>(args)...);
-  }
-
-private:
-  llvm::BumpPtrAllocator m_alloc;
-};
-
 class FPOProgramASTVisitorMergeDependent : public Visitor<> {
 public:
   void Visit(BinaryOpNode &binary, Node *&) override {
@@ -81,7 +68,8 @@ class FPOProgramASTVisitorResolveRegisterRefs : public Visitor<bool> {
 public:
   static bool
   Resolve(const llvm::DenseMap<llvm::StringRef, Node *> &dependent_programs,
-          llvm::Triple::ArchType arch_type, NodeAllocator &alloc, Node *&ast) {
+          llvm::Triple::ArchType arch_type, llvm::BumpPtrAllocator &alloc,
+          Node *&ast) {
     return FPOProgramASTVisitorResolveRegisterRefs(dependent_programs,
                                                    arch_type, alloc)
         .Dispatch(ast);
@@ -104,13 +92,13 @@ public:
 private:
   FPOProgramASTVisitorResolveRegisterRefs(
       const llvm::DenseMap<llvm::StringRef, Node *> &dependent_programs,
-      llvm::Triple::ArchType arch_type, NodeAllocator &alloc)
+      llvm::Triple::ArchType arch_type, llvm::BumpPtrAllocator &alloc)
       : m_dependent_programs(dependent_programs), m_arch_type(arch_type),
         m_alloc(alloc) {}
 
   const llvm::DenseMap<llvm::StringRef, Node *> &m_dependent_programs;
   llvm::Triple::ArchType m_arch_type;
-  NodeAllocator &m_alloc;
+  llvm::BumpPtrAllocator &m_alloc;
 };
 
 static uint32_t ResolveLLDBRegisterNum(llvm::StringRef reg_name, llvm::Triple::ArchType arch_type) {
@@ -145,7 +133,7 @@ bool FPOProgramASTVisitorResolveRegisterRefs::Visit(SymbolNode &symbol,
   if (reg_num == LLDB_INVALID_REGNUM)
     return false;
 
-  ref = m_alloc.makeNode<RegisterNode>(reg_num);
+  ref = MakeNode<RegisterNode>(m_alloc, reg_num);
   return true;
 }
 
@@ -227,95 +215,23 @@ void FPOProgramASTVisitorDWARFCodegen::Visit(UnaryOpNode &unary, Node *&) {
 } // namespace
 
 static bool ParseFPOSingleAssignmentProgram(llvm::StringRef program,
-                                            NodeAllocator &alloc,
+                                            llvm::BumpPtrAllocator &alloc,
                                             llvm::StringRef &register_name,
                                             Node *&ast) {
-  llvm::SmallVector<llvm::StringRef, 16> tokens;
-  llvm::SplitString(program, tokens, " ");
-
-  if (tokens.empty())
-    return false;
-
-  llvm::SmallVector<Node *, 4> eval_stack;
-
-  llvm::DenseMap<llvm::StringRef, BinaryOpNode::OpType> ops_binary = {
-      {"+", BinaryOpNode::Plus},
-      {"-", BinaryOpNode::Minus},
-      {"@", BinaryOpNode::Align},
-  };
-
-  llvm::DenseMap<llvm::StringRef, UnaryOpNode::OpType> ops_unary = {
-      {"^", UnaryOpNode::Deref},
-  };
-
-  constexpr llvm::StringLiteral ra_search_keyword = ".raSearch";
-
   // lvalue of assignment is always first token
   // rvalue program goes next
-  for (size_t i = 1; i < tokens.size(); ++i) {
-    llvm::StringRef cur = tokens[i];
-
-    auto ops_binary_it = ops_binary.find(cur);
-    if (ops_binary_it != ops_binary.end()) {
-      // token is binary operator
-      if (eval_stack.size() < 2) {
-        return false;
-      }
-      Node *right = eval_stack.pop_back_val();
-      Node *left = eval_stack.pop_back_val();
-      Node *node =
-          alloc.makeNode<BinaryOpNode>(ops_binary_it->second, *left, *right);
-      eval_stack.push_back(node);
-      continue;
-    }
-
-    auto ops_unary_it = ops_unary.find(cur);
-    if (ops_unary_it != ops_unary.end()) {
-      // token is unary operator
-      if (eval_stack.empty()) {
-        return false;
-      }
-      Node *operand = eval_stack.pop_back_val();
-      Node *node = alloc.makeNode<UnaryOpNode>(ops_unary_it->second, *operand);
-      eval_stack.push_back(node);
-      continue;
-    }
-
-    if (cur.startswith("$")) {
-      eval_stack.push_back(alloc.makeNode<SymbolNode>(cur));
-      continue;
-    }
-
-    if (cur == ra_search_keyword) {
-      // TODO: .raSearch is unsupported
-      return false;
-    }
-
-    uint32_t value;
-    if (!cur.getAsInteger(10, value)) {
-      // token is integer literal
-      eval_stack.push_back(alloc.makeNode<IntegerNode>(value));
-      continue;
-    }
-
-    // unexpected token
+  std::tie(register_name, program) = getToken(program);
+  if (register_name.empty())
     return false;
-  }
 
-  if (eval_stack.size() != 1) {
-    return false;
-  }
-
-  register_name = tokens[0];
-  ast = eval_stack.pop_back_val();
-
-  return true;
+  ast = Parse(program, alloc);
+  return ast != nullptr;
 }
 
 static Node *ParseFPOProgram(llvm::StringRef program,
                              llvm::StringRef register_name,
                              llvm::Triple::ArchType arch_type,
-                             NodeAllocator &alloc) {
+                             llvm::BumpPtrAllocator &alloc) {
   llvm::DenseMap<llvm::StringRef, Node *> dependent_programs;
 
   size_t cur = 0;
@@ -365,7 +281,7 @@ static Node *ParseFPOProgram(llvm::StringRef program,
 bool lldb_private::npdb::TranslateFPOProgramToDWARFExpression(
     llvm::StringRef program, llvm::StringRef register_name,
     llvm::Triple::ArchType arch_type, Stream &stream) {
-  NodeAllocator node_alloc;
+  llvm::BumpPtrAllocator node_alloc;
   Node *target_program =
       ParseFPOProgram(program, register_name, arch_type, node_alloc);
   if (target_program == nullptr) {

lldb/source/Symbol/CMakeLists.txt

@@ -26,6 +26,7 @@ add_lldb_library(lldbSymbol
   LineTable.cpp
   LocateSymbolFile.cpp
   ObjectFile.cpp
+  PostfixExpression.cpp
   Symbol.cpp
   SymbolContext.cpp
   SymbolFile.cpp

lldb/source/Symbol/PostfixExpression.cpp

@@ -0,0 +1,82 @@
+//===-- PostfixExpression.cpp -----------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements support for postfix expressions found in several symbol
+//  file formats, and their conversion to DWARF.
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Symbol/PostfixExpression.h"
+#include "llvm/ADT/StringExtras.h"
+
+using namespace lldb_private;
+using namespace lldb_private::postfix;
+
+static llvm::Optional<BinaryOpNode::OpType>
+GetBinaryOpType(llvm::StringRef token) {
+  if (token.size() != 1)
+    return llvm::None;
+  switch (token[0]) {
+  case '@':
+    return BinaryOpNode::Align;
+  case '-':
+    return BinaryOpNode::Minus;
+  case '+':
+    return BinaryOpNode::Plus;
+  }
+  return llvm::None;
+}
+
+static llvm::Optional<UnaryOpNode::OpType>
+GetUnaryOpType(llvm::StringRef token) {
+  if (token == "^")
+    return UnaryOpNode::Deref;
+  return llvm::None;
+}
+
+Node *postfix::Parse(llvm::StringRef expr, llvm::BumpPtrAllocator &alloc) {
+  llvm::SmallVector<Node *, 4> stack;
+
+  llvm::StringRef token;
+  while (std::tie(token, expr) = getToken(expr), !token.empty()) {
+    if (auto op_type = GetBinaryOpType(token)) {
+      // token is binary operator
+      if (stack.size() < 2)
+        return nullptr;
+
+      Node *right = stack.pop_back_val();
+      Node *left = stack.pop_back_val();
+      stack.push_back(MakeNode<BinaryOpNode>(alloc, *op_type, *left, *right));
+      continue;
+    }
+
+    if (auto op_type = GetUnaryOpType(token)) {
+      // token is unary operator
+      if (stack.empty())
+        return nullptr;
+
+      Node *operand = stack.pop_back_val();
+      stack.push_back(MakeNode<UnaryOpNode>(alloc, *op_type, *operand));
+      continue;
+    }
+
+    uint32_t value;
+    if (to_integer(token, value, 10)) {
+      // token is integer literal
+      stack.push_back(MakeNode<IntegerNode>(alloc, value));
+      continue;
+    }
+
+    stack.push_back(MakeNode<SymbolNode>(alloc, token));
+  }
+
+  if (stack.size() != 1)
+    return nullptr;
+
+  return stack.back();
+}

lldb/unittests/Symbol/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_lldb_unittest(SymbolTests
   LocateSymbolFileTest.cpp
+  PostfixExpressionTest.cpp
   TestClangASTContext.cpp
   TestDWARFCallFrameInfo.cpp
   TestType.cpp

lldb/unittests/Symbol/PostfixExpressionTest.cpp

@@ -0,0 +1,97 @@
+//===-- PostfixExpressionTest.cpp -------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Symbol/PostfixExpression.h"
+#include "llvm/Support/FormatVariadic.h"
+#include "llvm/Support/raw_ostream.h"
+#include "gtest/gtest.h"
+
+using namespace lldb_private;
+using namespace lldb_private::postfix;
+
+static std::string ToString(BinaryOpNode::OpType type) {
+  switch (type) {
+  case BinaryOpNode::Align:
+    return "@";
+  case BinaryOpNode::Minus:
+    return "-";
+  case BinaryOpNode::Plus:
+    return "+";
+  }
+  llvm_unreachable("Fully covered switch!");
+}
+
+static std::string ToString(UnaryOpNode::OpType type) {
+  switch (type) {
+  case UnaryOpNode::Deref:
+    return "^";
+  }
+  llvm_unreachable("Fully covered switch!");
+}
+
+struct ASTPrinter : public Visitor<std::string> {
+protected:
+  std::string Visit(BinaryOpNode &binary, Node *&) override {
+    return llvm::formatv("{0}({1}, {2})", ToString(binary.GetOpType()),
+                         Dispatch(binary.Left()), Dispatch(binary.Right()));
+  }
+
+  std::string Visit(IntegerNode &integer, Node *&) override {
+    return llvm::formatv("int({0})", integer.GetValue());
+  }
+
+  std::string Visit(RegisterNode &reg, Node *&) override {
+    return llvm::formatv("reg({0})", reg.GetRegNum());
+  }
+
+  std::string Visit(SymbolNode &symbol, Node *&) override {
+    return symbol.GetName();
+  }
+
+  std::string Visit(UnaryOpNode &unary, Node *&) override {
+    return llvm::formatv("{0}({1})", ToString(unary.GetOpType()),
+                         Dispatch(unary.Operand()));
+  }
+
+public:
+  static std::string Print(Node *node) {
+    if (node)
+      return ASTPrinter().Dispatch(node);
+    return "nullptr";
+  }
+};
+
+static std::string ParseAndStringify(llvm::StringRef expr) {
+  llvm::BumpPtrAllocator alloc;
+  return ASTPrinter::Print(Parse(expr, alloc));
+}
+
+TEST(PostfixExpression, Parse) {
+  EXPECT_EQ("int(47)", ParseAndStringify("47"));
+  EXPECT_EQ("$foo", ParseAndStringify("$foo"));
+  EXPECT_EQ("+(int(1), int(2))", ParseAndStringify("1 2 +"));
+  EXPECT_EQ("-(int(1), int(2))", ParseAndStringify("1 2 -"));
+  EXPECT_EQ("@(int(1), int(2))", ParseAndStringify("1 2 @"));
+  EXPECT_EQ("+(int(1), +(int(2), int(3)))", ParseAndStringify("1 2 3 + +"));
+  EXPECT_EQ("+(+(int(1), int(2)), int(3))", ParseAndStringify("1 2 + 3 +"));
+  EXPECT_EQ("^(int(1))", ParseAndStringify("1 ^"));
+  EXPECT_EQ("^(^(int(1)))", ParseAndStringify("1 ^ ^"));
+  EXPECT_EQ("^(+(int(1), ^(int(2))))", ParseAndStringify("1 2 ^ + ^"));
+  EXPECT_EQ("-($foo, int(47))", ParseAndStringify("$foo 47 -"));
+
+  EXPECT_EQ("nullptr", ParseAndStringify("+"));
+  EXPECT_EQ("nullptr", ParseAndStringify("^"));
+  EXPECT_EQ("nullptr", ParseAndStringify("1 +"));
+  EXPECT_EQ("nullptr", ParseAndStringify("1 2 ^"));
+  EXPECT_EQ("nullptr", ParseAndStringify("1 2 3 +"));
+  EXPECT_EQ("nullptr", ParseAndStringify("^ 1"));
+  EXPECT_EQ("nullptr", ParseAndStringify("+ 1 2"));
+  EXPECT_EQ("nullptr", ParseAndStringify("1 + 2"));
+  EXPECT_EQ("nullptr", ParseAndStringify("1 2"));
+  EXPECT_EQ("nullptr", ParseAndStringify(""));
+}