[llvm] r179391 - Add a comment about the PPC Interpretation64Bit bit

[Hal Finkel]

Author: hfinkel
Date: Fri Apr 12 13:17:38 2013
New Revision: 179391

URL: http://llvm.org/viewvc/llvm-project?rev=179391&view=rev
Log:
Add a comment about the PPC Interpretation64Bit bit

Modified:
    llvm/trunk/lib/Target/PowerPC/PPCInstrFormats.td

Modified: llvm/trunk/lib/Target/PowerPC/PPCInstrFormats.td
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/PPCInstrFormats.td?rev=179391&r1=179390&r2=179391&view=diff
==============================================================================
--- llvm/trunk/lib/Target/PowerPC/PPCInstrFormats.td (original)
+++ llvm/trunk/lib/Target/PowerPC/PPCInstrFormats.td Fri Apr 12 13:17:38 2013
@@ -38,6 +38,11 @@ class I<bits<6> opcode, dag OOL, dag IOL
 
   // Fields used for relation models.
   string BaseName = "";
+
+  // For cases where multiple instruction definitions really represent the
+  // same underlying instruction but with one definition for 64-bit arguments
+  // and one for 32-bit arguments, this bit breaks the degeneracy between
+  // the two forms and allows TableGen to generate mapping tables.
   bit Interpretation64Bit = 0;
 }