Cleanup and document MachineLocation.

Clarify documentation and API to make the difference between register and
register-indirect addressed locations more explicit. Put in a comment
to point out that with the current implementation we cannot specify
a register-indirect location with offset 0 (a breg 0 in DWARF).
No functionality change intended.

rdar://problem/13658587

llvm-svn: 180641

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/include/llvm/MC/MachineLocation.h b/llvm/include/llvm/MC/MachineLocation.h
index 5caad337f82..83c8b72ee4a 100644
--- a/llvm/include/llvm/MC/MachineLocation.h
+++ b/llvm/include/llvm/MC/MachineLocation.h
@@ -9,7 +9,7 @@
 // The MachineLocation class is used to represent a simple location in a machine
 // frame.  Locations will be one of two forms; a register or an address formed
 // from a base address plus an offset.  Register indirection can be specified by
-// using an offset of zero.
+// explicitly passing an offset to the constructor.
 //
 // The MachineMove class is used to represent abstract move operations in the
 // prolog/epilog of a compiled function.  A collection of these objects can be
@@ -37,8 +37,10 @@ public:
   };
   MachineLocation()
     : IsRegister(false), Register(0), Offset(0) {}
+  /// Create a direct register location.
   explicit MachineLocation(unsigned R)
     : IsRegister(true), Register(R), Offset(0) {}
+  /// Create a register-indirect location with an offset.
   MachineLocation(unsigned R, int O)
     : IsRegister(false), Register(R), Offset(O) {}
 
@@ -48,17 +50,20 @@ public:
   }
 
   // Accessors
+  bool isIndirect()      const { return !IsRegister; }
   bool isReg()           const { return IsRegister; }
   unsigned getReg()      const { return Register; }
   int getOffset()        const { return Offset; }
   void setIsRegister(bool Is)  { IsRegister = Is; }
   void setRegister(unsigned R) { Register = R; }
   void setOffset(int O)        { Offset = O; }
+  /// Make this location a direct register location.
   void set(unsigned R) {
     IsRegister = true;
     Register = R;
     Offset = 0;
   }
+  /// Make this location a register-indirect+offset location.
   void set(unsigned R, int O) {
     IsRegister = false;
     Register = R;