Add support for bottom-up SLP vectorization infrastructure.

This commit adds the infrastructure for performing bottom-up SLP vectorization (and other optimizations) on parallel computations.
The infrastructure has three potential users:

  1. The loop vectorizer needs to be able to vectorize AOS data structures such as (sum += A[i] + A[i+1]).

  2. The BB-vectorizer needs this infrastructure for bottom-up SLP vectorization, because bottom-up vectorization is faster to compute.

  3. A loop-roller needs to be able to analyze consecutive chains and roll them into a loop, in order to reduce code size. A loop roller does not need to create vector instructions, and this infrastructure separates the chain analysis from the vectorization.

This patch also includes a simple (100 LOC) bottom up SLP vectorizer that uses the infrastructure, and can vectorize this code:

void SAXPY(int *x, int *y, int a, int i) {
  x[i]   = a * x[i]   + y[i];
  x[i+1] = a * x[i+1] + y[i+1];
  x[i+2] = a * x[i+2] + y[i+2];
  x[i+3] = a * x[i+3] + y[i+3];
}



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179117 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 108 insertions, 0 deletions

diff --git a/lib/Transforms/Vectorize/VecUtils.h b/lib/Transforms/Vectorize/VecUtils.h
new file mode 100644
index 0000000000..b1c2b0c649
--- /dev/null
+++ b/lib/Transforms/Vectorize/VecUtils.h
@@ -0,0 +1,108 @@
+//===- VecUtils.cpp - Vectorization Utilities -----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This family of classes and functions manipulate vectors and chains of
+// vectors.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_VECTORIZE_AOSVECTORIZER_H
+#define  LLVM_TRANSFORMS_VECTORIZE_AOSVECTORIZER_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include <vector>
+
+using namespace llvm;
+
+namespace llvm {
+
+class BasicBlock; class Instruction; class Type;
+class VectorType; class StoreInst; class Value;
+class ScalarEvolution; class DataLayout;
+class TargetTransformInfo; class AliasAnalysis;
+
+/// Bottom Up SLP vectorization utility class.
+struct BoUpSLP  {
+  typedef SmallVector<Value*, 8> ValueList;
+  typedef SmallPtrSet<Value*, 16> ValueSet;
+  typedef SmallVector<StoreInst*, 8> StoreList;
+  static const int max_cost = 1<<20;
+
+  // \brief C'tor.
+  BoUpSLP(BasicBlock *Bb, ScalarEvolution *Se, DataLayout *Dl,
+         TargetTransformInfo *Tti, AliasAnalysis *Aa);
+
+  /// \returns true if the memory operations A and B are consecutive.
+  bool isConsecutiveAccess(Value *A, Value *B);
+
+  /// \brief Vectorize the tree that starts with the elements in \p VL.
+  /// \returns the vectorized value.
+  Value *vectorizeTree(ValueList &VL, int VF);
+
+  /// \returns the vectorization cost of the subtree that starts at \p VL.
+  /// A negative number means that this is profitable.
+  int getTreeRollCost(ValueList &VL, unsigned Depth);
+
+  /// \brief Take the pointer operand from the Load/Store instruction.
+  /// \returns NULL if this is not a valid Load/Store instruction.
+  static Value *getPointerOperand(Value *I);
+
+  /// \brief Take the address space operand from the Load/Store instruction.
+  /// \returns -1 if this is not a valid Load/Store instruction.
+  static unsigned getAddressSpaceOperand(Value *I);
+
+  /// \brief Attempts to order and vectorize a sequence of stores. This
+  /// function does a quadratic scan of the given stores.
+  /// \returns true if the basic block was modified.
+  bool vectorizeStores(StoreList &Stores, int costThreshold);
+
+  /// \brief Number all of the instructions in the block.
+  void numberInstructions();
+
+private:
+  /// \returns the scalarization cost for this type. Scalarization in this
+  /// context means the creation of vectors from a group of scalars.
+  int getScalarizationCost(Type *Ty);
+
+  /// \returns the AA location that is being access by the instruction.
+  AliasAnalysis::Location getLocation(Instruction *I);
+
+  /// \brief Checks if it is possible to sink an instruction from
+  /// \p Src to \p Dst.
+  /// \returns the pointer to the barrier instruction if we can't sink.
+  Value *isUnsafeToSink(Instruction *Src, Instruction *Dst);
+
+  /// \returns the instruction that appears last in the BB from \p VL.
+  /// Only consider the first \p VF elements.
+  Instruction *GetLastInstr(ValueList &VL, unsigned VF);
+
+  /// \returns a vector from a collection of scalars in \p VL.
+  Value *Scalarize(ValueList &VL, VectorType *Ty);
+
+  // Maps instructions to numbers and back.
+  SmallDenseMap<Value*, int> InstrIdx;
+  std::vector<Instruction*> InstrVec;
+  // A list of instructions to ignore while sinking
+  // memory instructions.
+  SmallSet<Value*, 8> MemBarrierIgnoreList;
+  // Analysis and block reference.
+  BasicBlock *BB;
+  ScalarEvolution *SE;
+  DataLayout *DL;
+  TargetTransformInfo *TTI;
+  AliasAnalysis *AA;
+};
+
+} // end of namespace
+# endif  //LLVM_TRANSFORMS_VECTORIZE_AOSVECTORIZER_H
+