[llvm-commits] [llvm] r123114 - /llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp

[Cameron Zwarich]

Author: zwarich
Date: Sun Jan  9 04:32:30 2011
New Revision: 123114

URL: http://llvm.org/viewvc/llvm-project?rev=123114&view=rev
Log:
Add an informative comment.

Modified:
    llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp

Modified: llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp?rev=123114&r1=123113&r2=123114&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp (original)
+++ llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp Sun Jan  9 04:32:30 2011
@@ -89,7 +89,15 @@
     /// Add a register in a new congruence class containing only itself.
     void addReg(unsigned);
 
-    /// Join the congruence classes of two registers.
+    /// Join the congruence classes of two registers. This function is biased
+    /// towards the left argument, i.e. after
+    ///
+    /// addReg(r2);
+    /// unionRegs(r1, r2);
+    ///
+    /// the leader of the unioned congruence class is the same as the leader of
+    /// r1's congruence class prior to the union. This is actually relied upon
+    /// in the copy insertion code.
     void unionRegs(unsigned, unsigned);
 
     /// Get the color of a register. The color is 0 if the register has been