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

1 files changed, 24 insertions, 8 deletions

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();