[llvm-commits] [llvm] r78139 - /llvm/trunk/lib/CodeGen/MachineSink.cpp

[Dan Gohman]

Author: djg
Date: Tue Aug  4 20:19:01 2009
New Revision: 78139

URL: http://llvm.org/viewvc/llvm-project?rev=78139&view=rev
Log:
Various comment fixes.

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

Modified: llvm/trunk/lib/CodeGen/MachineSink.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineSink.cpp?rev=78139&r1=78138&r2=78139&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/MachineSink.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineSink.cpp Tue Aug  4 20:19:01 2009
@@ -7,7 +7,12 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This pass 
+// This pass moves instructions into successor blocks, when possible, so that
+// they aren't executed on paths where their results aren't needed.
+//
+// This pass is not intended to be a replacement or a complete alternative
+// for an LLVM-IR-level sinking pass. It is only designed to sink simple
+// constructs that are not exposed before lowering and instruction selection.
 //
 //===----------------------------------------------------------------------===//
 
@@ -31,7 +36,7 @@
     const TargetInstrInfo *TII;
     MachineFunction       *CurMF; // Current MachineFunction
     MachineRegisterInfo  *RegInfo; // Machine register information
-    MachineDominatorTree *DT;   // Machine dominator tree for the current Loop
+    MachineDominatorTree *DT;   // Machine dominator tree
 
   public:
     static char ID; // Pass identification
@@ -152,7 +157,7 @@
   // also sink them down before their first use in the block.  This xform has to
   // be careful not to *increase* register pressure though, e.g. sinking
   // "x = y + z" down if it kills y and z would increase the live ranges of y
-  // and z only the shrink the live range of x.
+  // and z and only shrink the live range of x.
   
   // Loop over all the operands of the specified instruction.  If there is
   // anything we can't handle, bail out.