Check function data in symbol table against data in .eh_frame.

Summary:
At the moment we rely solely on the symbol table information to discover
function boundaries. However, similar information is contained in
.eh_frame. Verify that the information from these two sources is
consistent, and if it's not, then skip processing the functions with
conflicting information.

(cherry picked from FBD3043800)

bolt/BinaryFunction.h

@@ -109,10 +109,6 @@ class BinaryFunction {
   /// Alignment requirements for the function.
   uint64_t Alignment{1};
 
-  /// False if the function is too complex to reconstruct its control
-  /// flow graph and re-assemble.
-  bool IsSimple{true};
-
   /// True if this function needs to be emitted in two separate parts, one for
   /// the hot basic blocks and another for the cold basic blocks.
   bool IsSplit{false};
@@ -125,6 +121,10 @@ class BinaryFunction {
 
   BinaryContext &BC;
 
+  /// False if the function is too complex to reconstruct its control
+  /// flow graph and re-assemble.
+  bool IsSimple{true};
+
   /// The address for the code for this function in codegen memory.
   uint64_t ImageAddress{0};
 
@@ -326,9 +326,10 @@ class BinaryFunction {
 
 
   BinaryFunction(std::string Name, SymbolRef Symbol, SectionRef Section,
-                 uint64_t Address, uint64_t Size, BinaryContext &BC) :
+                 uint64_t Address, uint64_t Size, BinaryContext &BC,
+                 bool IsSimple = true) :
       Name(Name), Symbol(Symbol), Section(Section), Address(Address),
-      Size(Size), BC(BC), CodeSectionName(".text." + Name),
+      Size(Size), BC(BC), IsSimple(IsSimple), CodeSectionName(".text." + Name),
       FunctionNumber(++Count)
   {}
 

bolt/Exceptions.h

@@ -42,15 +42,25 @@ class CFIReaderWriter {
     }
   }
 
-  using FDEsMap = std::map<uint64_t, const dwarf::FDE *>;
-
   bool fillCFIInfoFor(BinaryFunction &Function) const;
 
   // Include a new EHFrame, updating the .eh_frame_hdr
   void rewriteHeaderFor(StringRef EHFrame, uint64_t EHFrameAddress,
                         uint64_t NewFrameHdrAddress,
                         ArrayRef<uint64_t> FailedAddresses);
 
+  using FDEsMap = std::map<uint64_t, const dwarf::FDE *>;
+  using fde_iterator = FDEsMap::const_iterator;
+
+  /// Get all FDEs discovered by this reader.
+  iterator_range<fde_iterator> fdes() const {
+    return iterator_range<fde_iterator>(FDEs.begin(), FDEs.end());
+  }
+
+  const FDEsMap &getFDEs() const {
+    return FDEs;
+  }
+
 private:
   const DWARFFrame &EHFrame;
   uint64_t FrameHdrAddress;

bolt/RewriteInstance.cpp

@@ -540,9 +540,10 @@ void RewriteInstance::run() {
     return;
   }
 
+  // Main "loop".
   discoverStorage();
-  readSymbolTable();
   readSpecialSections();
+  discoverFileObjects();
   disassembleFunctions();
   runOptimizationPasses();
   emitFunctions();
@@ -558,7 +559,7 @@ void RewriteInstance::run() {
   rewriteFile();
 }
 
-void RewriteInstance::readSymbolTable() {
+void RewriteInstance::discoverFileObjects() {
   std::string FileSymbolName;
 
   FileSymRefs.clear();
@@ -654,11 +655,45 @@ void RewriteInstance::readSymbolTable() {
       continue;
     }
 
+    // Checkout for conflicts with function data from FDEs.
+    bool IsSimple = true;
+    auto FDEI = CFIRdWrt->getFDEs().lower_bound(Address);
+    if (FDEI != CFIRdWrt->getFDEs().end()) {
+      auto &FDE = *FDEI->second;
+      if (FDEI->first != Address) {
+        // There's no matching starting address in FDE. Make sure the previous
+        // FDE does not contain this address.
+        if (FDEI != CFIRdWrt->getFDEs().begin()) {
+          --FDEI;
+          auto &PrevFDE = *FDEI->second;
+          auto PrevStart = PrevFDE.getInitialLocation();
+          auto PrevLength = PrevFDE.getAddressRange();
+          if (Address > PrevStart && Address < PrevStart + PrevLength) {
+            errs() << "BOLT-WARNING: function " << UniqueName
+                   << " is in conflict with FDE ["
+                   << Twine::utohexstr(PrevStart) << ", "
+                   << Twine::utohexstr(PrevStart + PrevLength)
+                   << "). Skipping.\n";
+            IsSimple = false;
+          }
+        }
+      } else if (FDE.getAddressRange() != SymbolSize) {
+        // Function addresses match but sizes differ.
+        errs() << "BOLT-WARNING: sizes differ for function " << UniqueName
+               << ". FDE : " << FDE.getAddressRange()
+               << "; symbol table : " << SymbolSize << ". Skipping.\n";
+
+        // Create maximum size non-simple function.
+        IsSimple = false;
+        SymbolSize = std::max(SymbolSize, FDE.getAddressRange());
+      }
+    }
+
     // Create the function and add to the map.
     BinaryFunctions.emplace(
         Address,
         BinaryFunction(UniqueName, Symbol, *Section, Address,
-                       SymbolSize, *BC)
+                       SymbolSize, *BC, IsSimple)
     );
   }
 }

bolt/RewriteInstance.h

@@ -125,9 +125,9 @@ class RewriteInstance {
   /// Run all the necessary steps to read, optimize and rewrite the binary.
   void run();
 
-  /// Populate array of binary functions and file symbols from file symbol
-  /// table.
-  void readSymbolTable();
+  /// Populate array of binary functions and other objects of interest
+  /// from meta data in the file.
+  void discoverFileObjects();
 
   /// Read .eh_frame, .eh_frame_hdr and .gcc_except_table sections for exception
   /// and stack unwinding information.