[llvm-commits] [llvm] r112437 - /llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp

[Dan Gohman]

Author: djg
Date: Sun Aug 29 10:27:08 2010
New Revision: 112437

URL: http://llvm.org/viewvc/llvm-project?rev=112437&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=112437&r1=112436&r2=112437&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Sun Aug 29 10:27:08 2010
@@ -1932,20 +1932,25 @@
 LSRUse *
 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
                                        const LSRUse &OrigLU) {
-  // Search all uses for the formula. This could be more clever. Ignore
-  // ICmpZero uses because they may contain formulae generated by
-  // GenerateICmpZeroScales, in which case adding fixup offsets may
-  // be invalid.
+  // Search all uses for the formula. This could be more clever.
   for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
     LSRUse &LU = Uses[LUIdx];
+    // Check whether this use is close enough to OrigLU, to see whether it's
+    // worthwhile looking through its formulae.
+    // Ignore ICmpZero uses because they may contain formulae generated by
+    // GenerateICmpZeroScales, in which case adding fixup offsets may
+    // be invalid.
     if (&LU != &OrigLU &&
         LU.Kind != LSRUse::ICmpZero &&
         LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
         LU.WidestFixupType == OrigLU.WidestFixupType &&
         LU.HasFormulaWithSameRegs(OrigF)) {
+      // Scan through this use's formulae.
       for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
            E = LU.Formulae.end(); I != E; ++I) {
         const Formula &F = *I;
+        // Check to see if this formula has the same registers and symbols
+        // as OrigF.
         if (F.BaseRegs == OrigF.BaseRegs &&
             F.ScaledReg == OrigF.ScaledReg &&
             F.AM.BaseGV == OrigF.AM.BaseGV &&
@@ -1953,12 +1958,16 @@
             LU.Kind) {
           if (F.AM.BaseOffs == 0)
             return &LU;
+          // This is the formula where all the registers and symbols matched;
+          // there aren't going to be any others. Since we declined it, we
+          // can skip the rest of the formulae and procede to the next LSRUse.
           break;
         }
       }
     }
   }
 
+  // Nothing looked good.
   return 0;
 }