Beginning of the Great Exception Handling Rewrite.

* Add a "landing pad" attribute to the BasicBlock.
* Modify the bitcode reader and writer to handle said attribute.

Later: The verifier will ensure that the landing pad attribute is used in the
appropriate manner. I.e., not applied to the entry block, and applied only to
basic blocks that are branched to via a `dispatch' instruction.

(This is a work-in-progress.)

llvm-svn: 129235

7 files changed, 49 insertions, 14 deletions

diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index 857fa1ef626..da26cb82106 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -587,6 +587,8 @@ lltok::Kind LLLexer::LexIdentifier() {
 
   KEYWORD(x);
   KEYWORD(blockaddress);
+
+  KEYWORD(landingpad);
 #undef KEYWORD
 
   // Keywords for types.
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 0c3237a6799..afd10a0826f 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -2918,6 +2918,11 @@ bool LLParser::ParseBasicBlock(PerFunctionState &PFS) {
   BasicBlock *BB = PFS.DefineBB(Name, NameLoc);
   if (BB == 0) return true;
 
+  if (Lex.getKind() == lltok::kw_landingpad) {
+    BB->setIsLandingPad();
+    Lex.Lex();
+  }
+
   std::string NameStr;
 
   // Parse the instructions in this block until we get a terminator.
diff --git a/llvm/lib/AsmParser/LLToken.h b/llvm/lib/AsmParser/LLToken.h
index 576da191aec..53cf8d87f35 100644
--- a/llvm/lib/AsmParser/LLToken.h
+++ b/llvm/lib/AsmParser/LLToken.h
@@ -125,6 +125,9 @@ namespace lltok {
     kw_extractelement, kw_insertelement, kw_shufflevector, kw_getresult,
     kw_extractvalue, kw_insertvalue, kw_blockaddress,
 
+    // Basic block attribute.
+    kw_landingpad,
+
     // Unsigned Valued tokens (UIntVal).
     GlobalID,          // @42
     LocalVarID,        // %42
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 8223f76bbbc..235519850f0 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -714,7 +714,8 @@ bool BitcodeReader::ParseValueSymbolTable() {
 
     // Read a record.
     Record.clear();
-    switch (Stream.ReadRecord(Code, Record)) {
+    unsigned VSTCode = Stream.ReadRecord(Code, Record);
+    switch (VSTCode) {
     default:  // Default behavior: unknown type.
       break;
     case bitc::VST_CODE_ENTRY: {  // VST_ENTRY: [valueid, namechar x N]
@@ -729,13 +730,17 @@ bool BitcodeReader::ParseValueSymbolTable() {
       ValueName.clear();
       break;
     }
-    case bitc::VST_CODE_BBENTRY: {
+    case bitc::VST_CODE_BBENTRY:
+    case bitc::VST_CODE_LPADENTRY: {
       if (ConvertToString(Record, 1, ValueName))
         return Error("Invalid VST_BBENTRY record");
       BasicBlock *BB = getBasicBlock(Record[0]);
       if (BB == 0)
         return Error("Invalid BB ID in VST_BBENTRY record");
 
+      if (VSTCode == bitc::VST_CODE_LPADENTRY)
+        BB->setIsLandingPad(true);
+
       BB->setName(StringRef(ValueName.data(), ValueName.size()));
       ValueName.clear();
       break;
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index e34137f6155..51c13bd5016 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -40,6 +40,7 @@ enum {
   VST_ENTRY_7_ABBREV,
   VST_ENTRY_6_ABBREV,
   VST_BBENTRY_6_ABBREV,
+  VST_LPADENTRY_6_ABBREV,
 
   // CONSTANTS_BLOCK abbrev id's.
   CONSTANTS_SETTYPE_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
@@ -1179,13 +1180,20 @@ static void WriteValueSymbolTable(const ValueSymbolTable &VST,
 
     unsigned AbbrevToUse = VST_ENTRY_8_ABBREV;
 
-    // VST_ENTRY:   [valueid, namechar x N]
-    // VST_BBENTRY: [bbid, namechar x N]
+    // VST_ENTRY:     [valueid, namechar x N]
+    // VST_BBENTRY:   [bbid, namechar x N]
+    // VST_LPADENTRY: [lpadid, namechar x N]
     unsigned Code;
-    if (isa<BasicBlock>(SI->getValue())) {
-      Code = bitc::VST_CODE_BBENTRY;
-      if (isChar6)
-        AbbrevToUse = VST_BBENTRY_6_ABBREV;
+    if (const BasicBlock *BB = dyn_cast<BasicBlock>(SI->getValue())) {
+      if (BB->isLandingPad()) {
+        Code = bitc::VST_CODE_LPADENTRY;
+        if (isChar6)
+          AbbrevToUse = VST_LPADENTRY_6_ABBREV;
+      } else {
+        Code = bitc::VST_CODE_BBENTRY;
+        if (isChar6)
+          AbbrevToUse = VST_BBENTRY_6_ABBREV;
+      }
     } else {
       Code = bitc::VST_CODE_ENTRY;
       if (isChar6)
@@ -1366,8 +1374,16 @@ static void WriteBlockInfo(const ValueEnumerator &VE, BitstreamWriter &Stream) {
                                    Abbv) != VST_BBENTRY_6_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
-
-
+  { // 6-bit char6 VST_LPADENTRY strings.
+    BitCodeAbbrev *Abbv = new BitCodeAbbrev();
+    Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_LPADENTRY));
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
+    if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
+                                   Abbv) != VST_LPADENTRY_6_ABBREV)
+      llvm_unreachable("Unexpected abbrev ordering!");
+  }
 
   { // SETTYPE abbrev for CONSTANTS_BLOCK.
     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
diff --git a/llvm/lib/VMCore/AsmWriter.cpp b/llvm/lib/VMCore/AsmWriter.cpp
index ffd367a7ada..a92c9bc668d 100644
--- a/llvm/lib/VMCore/AsmWriter.cpp
+++ b/llvm/lib/VMCore/AsmWriter.cpp
@@ -1687,8 +1687,13 @@ void AssemblyWriter::printBasicBlock(const BasicBlock *BB) {
     Out << "\n";
     PrintLLVMName(Out, BB->getName(), LabelPrefix);
     Out << ':';
+    if (BB->isLandingPad())
+      Out << " landingpad";
   } else if (!BB->use_empty()) {      // Don't print block # of no uses...
-    Out << "\n; <label>:";
+    Out << '\n';
+    if (BB->isLandingPad())
+      Out << "landingpad ";
+    Out << "; <label>:";
     int Slot = Machine.getLocalSlot(BB);
     if (Slot != -1)
       Out << Slot;
diff --git a/llvm/lib/VMCore/BasicBlock.cpp b/llvm/lib/VMCore/BasicBlock.cpp
index 955a0285b26..b46fab590f1 100644
--- a/llvm/lib/VMCore/BasicBlock.cpp
+++ b/llvm/lib/VMCore/BasicBlock.cpp
@@ -38,10 +38,10 @@ LLVMContext &BasicBlock::getContext() const {
 // are not in the public header file...
 template class llvm::SymbolTableListTraits<Instruction, BasicBlock>;
 
-
 BasicBlock::BasicBlock(LLVMContext &C, const Twine &Name, Function *NewParent,
                        BasicBlock *InsertBefore)
-  : Value(Type::getLabelTy(C), Value::BasicBlockVal), Parent(0) {
+  : Value(Type::getLabelTy(C), Value::BasicBlockVal), Parent(0),
+    IsLandingPad(false) {
 
   // Make sure that we get added to a function
   LeakDetector::addGarbageObject(this);
@@ -57,7 +57,6 @@ BasicBlock::BasicBlock(LLVMContext &C, const Twine &Name, Function *NewParent,
   setName(Name);
 }
 
-
 BasicBlock::~BasicBlock() {
   // If the address of the block is taken and it is being deleted (e.g. because
   // it is dead), this means that there is either a dangling constant expr