Add some comments explaining what MVT and EVT are, and how they differ.

[oota-llvm.git] / include / llvm / CodeGen / ValueTypes.h

diff --git a/include/llvm/CodeGen/ValueTypes.h b/include/llvm/CodeGen/ValueTypes.h
index 61b6d59c288d6a206df92fd7dd47459145f3f96a..9e583ef4d69c7991e08031ab67c5c3c995d78ec7 100644 (file)
--- a/include/llvm/CodeGen/ValueTypes.h
+++ b/include/llvm/CodeGen/ValueTypes.h
@@ -26,7 +26,10 @@ namespace llvm {
   class LLVMContext;
   struct EVT;
 
-  class MVT { // MVT = Machine Value Type
+  /// MVT - Machine Value Type.  Every type that is supported natively by some
+  /// processor targeted by LLVM occurs here.  This means that any legal value
+  /// type can be represented by a MVT.
+  class MVT {
   public:
     enum SimpleValueType {
       // If you change this numbering, you must change the values in
@@ -126,13 +129,13 @@ namespace llvm {
 
     MVT() : SimpleTy((SimpleValueType)(INVALID_SIMPLE_VALUE_TYPE)) {}
     MVT(SimpleValueType SVT) : SimpleTy(SVT) { }
-    
+
     bool operator>(const MVT& S)  const { return SimpleTy >  S.SimpleTy; }
     bool operator<(const MVT& S)  const { return SimpleTy <  S.SimpleTy; }
     bool operator==(const MVT& S) const { return SimpleTy == S.SimpleTy; }
     bool operator>=(const MVT& S) const { return SimpleTy >= S.SimpleTy; }
     bool operator<=(const MVT& S) const { return SimpleTy <= S.SimpleTy; }
-    
+
     /// isFloatingPoint - Return true if this is a FP, or a vector FP type.
     bool isFloatingPoint() const {
       return ((SimpleTy >= MVT::f32 && SimpleTy <= MVT::ppcf128) ||
@@ -151,14 +154,14 @@ namespace llvm {
       return (SimpleTy >= MVT::FIRST_VECTOR_VALUETYPE &&
               SimpleTy <= MVT::LAST_VECTOR_VALUETYPE);
     }
-    
+
     /// isPow2VectorType - Returns true if the given vector is a power of 2.
     bool isPow2VectorType() const {
       unsigned NElts = getVectorNumElements();
       return !(NElts & (NElts - 1));
     }
 
-    /// getPow2VectorType - Widens the length of the given vector EVT up to
+    /// getPow2VectorType - Widens the length of the given vector MVT up to
     /// the nearest power of 2 and returns that type.
     MVT getPow2VectorType() const {
       if (isPow2VectorType())
@@ -174,7 +177,7 @@ namespace llvm {
     MVT getScalarType() const {
       return isVector() ? getVectorElementType() : *this;
     }
-    
+
     MVT getVectorElementType() const {
       switch (SimpleTy) {
       default:
@@ -202,7 +205,7 @@ namespace llvm {
       case v4f64: return f64;
       }
     }
-    
+
     unsigned getVectorNumElements() const {
       switch (SimpleTy) {
       default:
@@ -230,7 +233,7 @@ namespace llvm {
       case v1i64: return 1;
       }
     }
-    
+
     unsigned getSizeInBits() const {
       switch (SimpleTy) {
       case iPTR:
@@ -276,7 +279,7 @@ namespace llvm {
       case v8i64: return 512;
       }
     }
-    
+
     static MVT getFloatingPointVT(unsigned BitWidth) {
       switch (BitWidth) {
       default:
@@ -291,7 +294,7 @@ namespace llvm {
         return MVT::f128;
       }
     }
-    
+
     static MVT getIntegerVT(unsigned BitWidth) {
       switch (BitWidth) {
       default:
@@ -310,7 +313,7 @@ namespace llvm {
         return MVT::i128;
       }
     }
-    
+
     static MVT getVectorVT(MVT VT, unsigned NumElements) {
       switch (VT.SimpleTy) {
       default:
@@ -353,7 +356,11 @@ namespace llvm {
     }
   };
 
-  struct EVT { // EVT = Extended Value Type
+
+  /// EVT - Extended Value Type.  Capable of holding value types which are not
+  /// native for any processor (such as the i12345 type), as well as the types
+  /// a MVT can represent.
+  struct EVT {
   private:
     MVT V;
     const Type *LLVMTy;
@@ -530,7 +537,7 @@ namespace llvm {
     EVT getScalarType() const {
       return isVector() ? getVectorElementType() : *this;
     }
-    
+
     /// getVectorElementType - Given a vector type, return the type of
     /// each element.
     EVT getVectorElementType() const {