[llvm-commits] [llvm] r104268 - /llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

[Dan Gohman]

Author: djg
Date: Thu May 20 15:00:41 2010
New Revision: 104268

URL: http://llvm.org/viewvc/llvm-project?rev=104268&view=rev
Log:
Add some comments.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp?rev=104268&r1=104267&r2=104268&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Thu May 20 15:00:41 2010
@@ -2811,6 +2811,9 @@
       bool Any = false;
       for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
         Formula &F = LU.Formulae[i];
+        // Look for a formula with a constant or GV in a register. If the use
+        // also has a formula with that same value in an immediate field,
+        // delete the one that uses a register.
         for (SmallVectorImpl<const SCEV *>::const_iterator
              I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
           if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
@@ -2861,6 +2864,8 @@
                     "separated by a constant offset will use the same "
                     "registers.\n");
 
+    // This is especially useful for unrolled loops.
+
     for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
       LSRUse &LU = Uses[LUIdx];
       for (size_t FIdx = 0, NumForms = LU.Formulae.size();
@@ -3074,6 +3079,7 @@
   DenseSet<const SCEV *> VisitedRegs;
   Workspace.reserve(Uses.size());
 
+  // SolveRecurse does all the work.
   SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
                CurRegs, VisitedRegs);