first part of implementation of abbrevs. The writer isn't fully there yet and the

reader doesn't handle them at all yet.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36363 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Bitcode/BitCodes.h

@@ -18,6 +18,10 @@
 #ifndef LLVM_BITCODE_BITCODES_H
 #define LLVM_BITCODE_BITCODES_H
 
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/DataTypes.h"
+#include <cassert>
+
 namespace llvm {
 namespace bitc {
   enum StandardWidths {
@@ -31,16 +35,71 @@ namespace bitc {
   enum FixedCodes {
     END_BLOCK = 0,  // Must be zero to guarantee termination for broken bitcode.
     ENTER_SUBBLOCK = 1,
+
+    /// DEFINE_ABBREV - Defines an abbrev for the current block.  It consists
+    /// of a vbr5 for # operand infos.  Each operand info is emitted with a
+    /// single bit to indicate if it is a literal encoding.  If so, the value is
+    /// emitted with a vbr8.  If not, the encoding is emitted as 3 bits followed
+    /// by the info value as a vbr5 if needed.
+    DEFINE_ABBREV = 2, 
     
-    // Two codes are reserved for defining abbrevs and for emitting an
-    // unabbreviated record.
-    DEFINE_ABBREVS = 2,
+    // UNABBREV_RECORDs are emitted with a vbr6 for the record code, followed by
+    // a vbr6 for the # operands, followed by vbr6's for each operand.
     UNABBREV_RECORD = 3,
     
     // This is not a code, this is a marker for the first abbrev assignment.
     FIRST_ABBREV = 4
   };
 } // End bitc namespace
+
+/// BitCodeAbbrevOp - This describes one or more operands in an abbreviation.
+/// This is actually a union of two different things:
+///   1. It could be a literal integer value ("the operand is always 17").
+///   2. It could be an encoding specification ("this operand encoded like so").
+///
+class BitCodeAbbrevOp {
+  uint64_t Val;        // A literal value or data for an encoding.
+  bool IsLiteral : 1;  // Indicate whether this is a literal value or not.
+  unsigned Enc   : 3;  // The encoding to use.
+public:
+  enum Encoding {
+    FixedWidth = 1,   // A fixed with field, Val specifies number of bits.
+    VBR        = 2   // A VBR field where Val specifies the width of each chunk.
+  };
+    
+  BitCodeAbbrevOp(uint64_t V) :  Val(V), IsLiteral(true) {}
+  BitCodeAbbrevOp(Encoding E, uint64_t Data)
+    : Val(Data), IsLiteral(false), Enc(E) {}
+  
+  bool isLiteral() const { return IsLiteral; }
+  bool isEncoding() const { return !IsLiteral; }
+
+  // Accessors for literals.
+  uint64_t getLiteralValue() const { assert(isLiteral()); return Val; }
+  
+  // Accessors for encoding info.
+  Encoding getEncoding() const { assert(isEncoding()); return (Encoding)Enc; }
+  uint64_t getEncodingData() const { assert(isEncoding()); return Val; }
+  
+  bool hasEncodingData() const { return hasEncodingData(getEncoding()); }
+  static bool hasEncodingData(Encoding E) {
+    return true; 
+  }
+};
+
+class BitCodeAbbrev {
+  SmallVector<BitCodeAbbrevOp, 8> OperandList;
+public:
+  
+  unsigned getNumOperandInfos() const { return OperandList.size(); }
+  const BitCodeAbbrevOp &getOperandInfo(unsigned N) const {
+    return OperandList[N];
+  }
+  
+  void Add(const BitCodeAbbrevOp &OpInfo) {
+    OperandList.push_back(OpInfo);
+  }
+};
 } // End llvm namespace
 
 #endif