Fix IntegerType::MAX_INT_BITS value

[andreybokhanko]

Summary

IntegerType::MAX_INT_BITS is apparently not in sync with Type::SubclassData size. This patch fixes this.

Not sure it would be better to introduce a #define or something in Type.h with SubclassData's size and use it in both places. I haven't seen a precedent elsewhere in llvm, so simply added a comment.

[andreybokhanko]

Ping!

[rnk]

lgtm

[andreybokhanko]

Reid, thanks for looking at this!

Yours,
Andrey

include/llvm/IR/DerivedTypes.h

protected:
   explicit IntegerType(LLVMContext &C, unsigned NumBits) : Type(C, IntegerTyID){
     setSubclassData(NumBits);
   }
 
 public:
   /// This enum is just used to hold constants we need for IntegerType.
   enum {
     MIN_INT_BITS = 1,        ///< Minimum number of bits that can be specified
-    MAX_INT_BITS = (1<<23)-1 ///< Maximum number of bits that can be specified
+    MAX_INT_BITS = (1<<24)-1 ///< Maximum number of bits that can be specified
       ///< Note that bit width is stored in the Type classes SubclassData field
-      ///< which has 23 bits. This yields a maximum bit width of 8,388,607 bits.
+      ///< which has 24 bits. This yields a maximum bit width of 16,777,215
+      ///< bits.
   };
 
   /// This static method is the primary way of constructing an IntegerType.
   /// If an IntegerType with the same NumBits value was previously instantiated,
   /// that instance will be returned. Otherwise a new one will be created. Only
   /// one instance with a given NumBits value is ever created.
   /// @brief Get or create an IntegerType instance.
   static IntegerType *get(LLVMContext &C, unsigned NumBits);

include/llvm/IR/Type.h

public:
   };
 
 private:
   /// This refers to the LLVMContext in which this type was uniqued.
   LLVMContext &Context;
 
   TypeID   ID : 8;            // The current base type of this type.
   unsigned SubclassData : 24; // Space for subclasses to store data.
+                              // Note that this should be synchronized with
+                              // MAX_INT_BITS value in IntegerType class.
 
 protected:
   friend class LLVMContextImpl;
   explicit Type(LLVMContext &C, TypeID tid)
     : Context(C), ID(tid), SubclassData(0),
       NumContainedTys(0), ContainedTys(nullptr) {}
   ~Type() = default;
 

test/Assembler/invalid-inttype.ll

+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+
+; i16777216 is the smallest integer type that can't be represented in LLVM IR
+@i2 = common global i16777216 0, align 4
+; CHECK: expected type

test/Assembler/max-inttype.ll

+; RUN: llvm-as < %s | llvm-dis
+
+; i16777215 is the maximum integer type represented in LLVM IR
+@i2 = common global i16777215 0, align 4