The JIT calls TidyLandingPads to tidy up the landing pads. However, because the

JIT doesn't use the MC back-end asm printer to emit labels that it uses, the
section for the MCSymbol is never set. And thus the MCSymbol for the EH label
isn't marked as "defined". Because of that, TidyLandingPads removes the needed
landing pads from the JIT output. This breaks EH for every JIT program.

This is a work-around for this limitation. We pass in the label locations
map. If the label has a non-zero value, then it was "emitted" by the JIT and
TidyLandingPads shouldn't remove that label.

A nicer solution would be to mark the MCSymbol as "used" by the JIT and not rely
upon the section being set to determine if it's defined or not.

llvm-svn: 101453

llvm/include/llvm/CodeGen/JITCodeEmitter.h

@@ -21,6 +21,7 @@
 #include "llvm/System/DataTypes.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/CodeGen/MachineCodeEmitter.h"
+#include "llvm/ADT/DenseMap.h"
 
 using namespace std;
 
@@ -324,6 +325,10 @@ public:
   /// Specifies the MachineModuleInfo object. This is used for exception handling
   /// purposes.
   virtual void setModuleInfo(MachineModuleInfo* Info) = 0;
+
+  /// getLabelLocations - Return the label locations map of the label IDs to
+  /// their address.
+  virtual DenseMap<MCSymbol*, uintptr_t> *getLabelLocations() { return 0; }
 };
 
 } // End llvm namespace

llvm/include/llvm/CodeGen/MachineModuleInfo.h

@@ -295,7 +295,7 @@ public:
 
   /// TidyLandingPads - Remap landing pad labels and remove any deleted landing
   /// pads.
-  void TidyLandingPads();
+  void TidyLandingPads(DenseMap<MCSymbol*, uintptr_t> *LPMap = 0);
                         
   /// getLandingPads - Return a reference to the landing pad info for the
   /// current function.

llvm/lib/CodeGen/MachineModuleInfo.cpp

@@ -450,10 +450,12 @@ void MachineModuleInfo::addCleanup(MachineBasicBlock *LandingPad) {
 
 /// TidyLandingPads - Remap landing pad labels and remove any deleted landing
 /// pads.
-void MachineModuleInfo::TidyLandingPads() {
+void MachineModuleInfo::TidyLandingPads(DenseMap<MCSymbol*, uintptr_t> *LPMap) {
   for (unsigned i = 0; i != LandingPads.size(); ) {
     LandingPadInfo &LandingPad = LandingPads[i];
-    if (LandingPad.LandingPadLabel && !LandingPad.LandingPadLabel->isDefined())
+    if (LandingPad.LandingPadLabel &&
+        !LandingPad.LandingPadLabel->isDefined() &&
+        (!LPMap || (*LPMap)[LandingPad.LandingPadLabel] == 0))
       LandingPad.LandingPadLabel = 0;
 
     // Special case: we *should* emit LPs with null LP MBB. This indicates
@@ -466,7 +468,10 @@ void MachineModuleInfo::TidyLandingPads() {
     for (unsigned j = 0, e = LandingPads[i].BeginLabels.size(); j != e; ++j) {
       MCSymbol *BeginLabel = LandingPad.BeginLabels[j];
       MCSymbol *EndLabel = LandingPad.EndLabels[j];
-      if (BeginLabel->isDefined() && EndLabel->isDefined()) continue;
+      if ((BeginLabel->isDefined() ||
+           (LPMap && (*LPMap)[BeginLabel] != 0)) &&
+          (EndLabel->isDefined() ||
+           (LPMap && (*LPMap)[EndLabel] != 0))) continue;
       
       LandingPad.BeginLabels.erase(LandingPad.BeginLabels.begin() + j);
       LandingPad.EndLabels.erase(LandingPad.EndLabels.begin() + j);

llvm/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp

@@ -199,7 +199,7 @@ unsigned char* JITDwarfEmitter::EmitExceptionTable(MachineFunction* MF,
   assert(MMI && "MachineModuleInfo not registered!");
 
   // Map all labels and get rid of any dead landing pads.
-  MMI->TidyLandingPads();
+  MMI->TidyLandingPads(JCE->getLabelLocations());
 
   const std::vector<const GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
   const std::vector<unsigned> &FilterIds = MMI->getFilterIds();
@@ -780,7 +780,7 @@ JITDwarfEmitter::GetExceptionTableSizeInBytes(MachineFunction* MF) const {
   unsigned FinalSize = 0;
 
   // Map all labels and get rid of any dead landing pads.
-  MMI->TidyLandingPads();
+  MMI->TidyLandingPads(JCE->getLabelLocations());
 
   const std::vector<const GlobalVariable *> &TypeInfos = MMI->getTypeInfos();
   const std::vector<unsigned> &FilterIds = MMI->getFilterIds();

llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp

@@ -23,6 +23,7 @@
 #include "llvm/Analysis/DebugInfo.h"
 #include "llvm/CodeGen/JITCodeEmitter.h"
 #include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineCodeInfo.h"
 #include "llvm/CodeGen/MachineConstantPool.h"
 #include "llvm/CodeGen/MachineJumpTableInfo.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
@@ -30,8 +31,8 @@
 #include "llvm/ExecutionEngine/GenericValue.h"
 #include "llvm/ExecutionEngine/JITEventListener.h"
 #include "llvm/ExecutionEngine/JITMemoryManager.h"
-#include "llvm/CodeGen/MachineCodeInfo.h"
 #include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetJITInfo.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
@@ -43,7 +44,6 @@
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/System/Disassembler.h"
 #include "llvm/System/Memory.h"
-#include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
@@ -463,6 +463,10 @@ namespace {
       LabelLocations[Label] = getCurrentPCValue();
     }
 
+    virtual DenseMap<MCSymbol*, uintptr_t> *getLabelLocations() {
+      return &LabelLocations;
+    }
+
     virtual uintptr_t getLabelAddress(MCSymbol *Label) const {
       assert(LabelLocations.count(Label) && "Label not emitted!");
       return LabelLocations.find(Label)->second;