[PATCH] Refactor identification of reductions and expose them as utility functions

[Adam Nemet]

================
Comment at: include/llvm/Transforms/Utils/LoopUtils.h:45-62
@@ -44,1 +44,20 @@
 
+/// This enum represents the kinds of reductions that we support.
+enum ReductionKind {
+  RK_NoReduction,   ///< Not a reduction.
+  RK_IntegerAdd,    ///< Sum of integers.
+  RK_IntegerMult,   ///< Product of integers.
+  RK_IntegerOr,     ///< Bitwise or logical OR of numbers.
+  RK_IntegerAnd,    ///< Bitwise or logical AND of numbers.
+  RK_IntegerXor,    ///< Bitwise or logical XOR of numbers.
+  RK_IntegerMinMax, ///< Min/max implemented in terms of select(cmp()).
+  RK_FloatAdd,      ///< Sum of floats.
+  RK_FloatMult,     ///< Product of floats.
+  RK_FloatMinMax    ///< Min/max implemented in terms of select(cmp()).
+};
+
+// This enum represents the kind of minmax reduction.
+enum MinMaxReductionKind {
+  MRK_Invalid,
+  MRK_UIntMin,
+  MRK_UIntMax,
----------------
I haven't dealt with this part of the vectorizer yet so I only have general comments about some interface improvements, now, that these interfaces are made public.

Are these enums local to the structures that follow right after?  If yes, they should be local to those structs.

================
Comment at: include/llvm/Transforms/Utils/LoopUtils.h:123-126
@@ +122,6 @@
+
+bool AddReductionVar(PHINode *Phi, ReductionKind Kind, Loop *TheLoop,
+                     bool HasFunNoNaNAttr, ReductionDescriptor &RedDes);
+
+bool isReductionPHI(PHINode *Phi, Loop *TheLoop, ReductionDescriptor &RedDes);
+
----------------
These are missing comments.  Also if they operate on a ReductionDesc, they should probably made a member function.  And possibly turning the struct into classes to describe the public interface of the class.

================
Comment at: include/llvm/Transforms/Utils/LoopUtils.h:128-130
@@ +127,5 @@
+
+bool hasMultipleUsesOf(Instruction *I, SmallPtrSetImpl<Instruction *> &Insts);
+
+bool areAllUsesIn(Instruction *I, SmallPtrSetImpl<Instruction *> &Set);
+
----------------
These don't look like loop-related utilities.  Are you using these in your pass?

In that case you either want to move them to Instruction.h or make them static member of the above classes if these are specific to the algorithm finding reductions.

http://reviews.llvm.org/D9046

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