- Fix description of SUBREG_TO_REG. It's not going to generate a zext. But it

is used to assert that an *implicit* zext is performed.

- Fix grammar-o in INSERT_SUBREG. (required reformatting)

llvm-svn: 105735

llvm/include/llvm/Target/TargetOpcodes.h

@@ -36,22 +36,21 @@ namespace TargetOpcode {
     /// truncation operations on target architectures which support it.
     EXTRACT_SUBREG = 6,
     
-    /// INSERT_SUBREG - This instruction takes three operands: a register
-    /// that has subregisters, a register providing an insert value, and a
-    /// subregister index. It returns the value of the first register with
-    /// the value of the second register inserted. The first register is
-    /// often defined by an IMPLICIT_DEF, as is commonly used to implement
+    /// INSERT_SUBREG - This instruction takes three operands: a register that
+    /// has subregisters, a register providing an insert value, and a
+    /// subregister index. It returns the value of the first register with the
+    /// value of the second register inserted. The first register is often
+    /// defined by an IMPLICIT_DEF, because it is commonly used to implement
     /// anyext operations on target architectures which support it.
     INSERT_SUBREG = 7,
     
     /// IMPLICIT_DEF - This is the MachineInstr-level equivalent of undef.
     IMPLICIT_DEF = 8,
     
-    /// SUBREG_TO_REG - This instruction is similar to INSERT_SUBREG except
-    /// that the first operand is an immediate integer constant. This constant
-    /// is often zero, as is commonly used to implement zext operations on
-    /// target architectures which support it, such as with x86-64 (with
-    /// zext from i32 to i64 via implicit zero-extension).
+    /// SUBREG_TO_REG - This instruction is similar to INSERT_SUBREG except that
+    /// the first operand is an immediate integer constant. This constant is
+    /// often zero, because it is commonly used to assert that the instruction
+    /// defining the register implicitly clears the high bits.
     SUBREG_TO_REG = 9,
     
     /// COPY_TO_REGCLASS - This instruction is a placeholder for a plain