Move delinearization from SCEVAddRecExpr to ScalarEvolution

The expressions we delinearize do not necessarily have to have a SCEVAddRecExpr
at the outermost level. At this moment, the additional flexibility  is not
exploited in LLVM itself, but in Polly we will soon soonish use this
functionality. For LLVM, this change should not affect existing functionality
(which is covered by test/Analysis/Delinearization/)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240952 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h
index 1d1bd67b61ff5970a727ef7714e60669ff1b6221..d47cab829cedba26e44f97a332846fe47a07a134 100644 (file)
--- a/include/llvm/Analysis/ScalarEvolution.h
+++ b/include/llvm/Analysis/ScalarEvolution.h
@@ -954,6 +954,86 @@ namespace llvm {
     void print(raw_ostream &OS, const Module* = nullptr) const override;
     void verifyAnalysis() const override;
 
+    /// Collect parametric terms occurring in step expressions.
+    void collectParametricTerms(const SCEV *Expr,
+                                SmallVectorImpl<const SCEV *> &Terms);
+
+
+
+    /// Return in Subscripts the access functions for each dimension in Sizes.
+    void computeAccessFunctions(const SCEV *Expr,
+                                SmallVectorImpl<const SCEV *> &Subscripts,
+                                SmallVectorImpl<const SCEV *> &Sizes);
+
+    /// Split this SCEVAddRecExpr into two vectors of SCEVs representing the
+    /// subscripts and sizes of an array access.
+    ///
+    /// The delinearization is a 3 step process: the first two steps compute the
+    /// sizes of each subscript and the third step computes the access functions
+    /// for the delinearized array:
+    ///
+    /// 1. Find the terms in the step functions
+    /// 2. Compute the array size
+    /// 3. Compute the access function: divide the SCEV by the array size
+    ///    starting with the innermost dimensions found in step 2. The Quotient
+    ///    is the SCEV to be divided in the next step of the recursion. The
+    ///    Remainder is the subscript of the innermost dimension. Loop over all
+    ///    array dimensions computed in step 2.
+    ///
+    /// To compute a uniform array size for several memory accesses to the same
+    /// object, one can collect in step 1 all the step terms for all the memory
+    /// accesses, and compute in step 2 a unique array shape. This guarantees
+    /// that the array shape will be the same across all memory accesses.
+    ///
+    /// FIXME: We could derive the result of steps 1 and 2 from a description of
+    /// the array shape given in metadata.
+    ///
+    /// Example:
+    ///
+    /// A[][n][m]
+    ///
+    /// for i
+    ///   for j
+    ///     for k
+    ///       A[j+k][2i][5i] =
+    ///
+    /// The initial SCEV:
+    ///
+    /// A[{{{0,+,2*m+5}_i, +, n*m}_j, +, n*m}_k]
+    ///
+    /// 1. Find the different terms in the step functions:
+    /// -> [2*m, 5, n*m, n*m]
+    ///
+    /// 2. Compute the array size: sort and unique them
+    /// -> [n*m, 2*m, 5]
+    /// find the GCD of all the terms = 1
+    /// divide by the GCD and erase constant terms
+    /// -> [n*m, 2*m]
+    /// GCD = m
+    /// divide by GCD -> [n, 2]
+    /// remove constant terms
+    /// -> [n]
+    /// size of the array is A[unknown][n][m]
+    ///
+    /// 3. Compute the access function
+    /// a. Divide {{{0,+,2*m+5}_i, +, n*m}_j, +, n*m}_k by the innermost size m
+    /// Quotient: {{{0,+,2}_i, +, n}_j, +, n}_k
+    /// Remainder: {{{0,+,5}_i, +, 0}_j, +, 0}_k
+    /// The remainder is the subscript of the innermost array dimension: [5i].
+    ///
+    /// b. Divide Quotient: {{{0,+,2}_i, +, n}_j, +, n}_k by next outer size n
+    /// Quotient: {{{0,+,0}_i, +, 1}_j, +, 1}_k
+    /// Remainder: {{{0,+,2}_i, +, 0}_j, +, 0}_k
+    /// The Remainder is the subscript of the next array dimension: [2i].
+    ///
+    /// The subscript of the outermost dimension is the Quotient: [j+k].
+    ///
+    /// Overall, we have: A[][n][m], and the access function: A[j+k][2i][5i].
+    void delinearize(const SCEV *Expr,
+                     SmallVectorImpl<const SCEV *> &Subscripts,
+                     SmallVectorImpl<const SCEV *> &Sizes,
+                     const SCEV *ElementSize);
+
   private:
     /// Compute the backedge taken count knowing the interval difference, the
     /// stride and presence of the equality in the comparison.

diff --git a/include/llvm/Analysis/ScalarEvolutionExpressions.h b/include/llvm/Analysis/ScalarEvolutionExpressions.h
index ff82db19b9e7ed881d7284deff3a712d350373de..da24de281d4757e2a26383324e4345963daeddad 100644 (file)
--- a/include/llvm/Analysis/ScalarEvolutionExpressions.h
+++ b/include/llvm/Analysis/ScalarEvolutionExpressions.h
@@ -356,84 +356,6 @@ namespace llvm {
     static inline bool classof(const SCEV *S) {
       return S->getSCEVType() == scAddRecExpr;
     }
-
-    /// Collect parametric terms occurring in step expressions.
-    void collectParametricTerms(ScalarEvolution &SE,
-                                SmallVectorImpl<const SCEV *> &Terms) const;
-
-    /// Return in Subscripts the access functions for each dimension in Sizes.
-    void computeAccessFunctions(ScalarEvolution &SE,
-                                SmallVectorImpl<const SCEV *> &Subscripts,
-                                SmallVectorImpl<const SCEV *> &Sizes) const;
-
-    /// Split this SCEVAddRecExpr into two vectors of SCEVs representing the
-    /// subscripts and sizes of an array access.
-    ///
-    /// The delinearization is a 3 step process: the first two steps compute the
-    /// sizes of each subscript and the third step computes the access functions
-    /// for the delinearized array:
-    ///
-    /// 1. Find the terms in the step functions
-    /// 2. Compute the array size
-    /// 3. Compute the access function: divide the SCEV by the array size
-    ///    starting with the innermost dimensions found in step 2. The Quotient
-    ///    is the SCEV to be divided in the next step of the recursion. The
-    ///    Remainder is the subscript of the innermost dimension. Loop over all
-    ///    array dimensions computed in step 2.
-    ///
-    /// To compute a uniform array size for several memory accesses to the same
-    /// object, one can collect in step 1 all the step terms for all the memory
-    /// accesses, and compute in step 2 a unique array shape. This guarantees
-    /// that the array shape will be the same across all memory accesses.
-    ///
-    /// FIXME: We could derive the result of steps 1 and 2 from a description of
-    /// the array shape given in metadata.
-    ///
-    /// Example:
-    ///
-    /// A[][n][m]
-    ///
-    /// for i
-    ///   for j
-    ///     for k
-    ///       A[j+k][2i][5i] =
-    ///
-    /// The initial SCEV:
-    ///
-    /// A[{{{0,+,2*m+5}_i, +, n*m}_j, +, n*m}_k]
-    ///
-    /// 1. Find the different terms in the step functions:
-    /// -> [2*m, 5, n*m, n*m]
-    ///
-    /// 2. Compute the array size: sort and unique them
-    /// -> [n*m, 2*m, 5]
-    /// find the GCD of all the terms = 1
-    /// divide by the GCD and erase constant terms
-    /// -> [n*m, 2*m]
-    /// GCD = m
-    /// divide by GCD -> [n, 2]
-    /// remove constant terms
-    /// -> [n]
-    /// size of the array is A[unknown][n][m]
-    ///
-    /// 3. Compute the access function
-    /// a. Divide {{{0,+,2*m+5}_i, +, n*m}_j, +, n*m}_k by the innermost size m
-    /// Quotient: {{{0,+,2}_i, +, n}_j, +, n}_k
-    /// Remainder: {{{0,+,5}_i, +, 0}_j, +, 0}_k
-    /// The remainder is the subscript of the innermost array dimension: [5i].
-    ///
-    /// b. Divide Quotient: {{{0,+,2}_i, +, n}_j, +, n}_k by next outer size n
-    /// Quotient: {{{0,+,0}_i, +, 1}_j, +, 1}_k
-    /// Remainder: {{{0,+,2}_i, +, 0}_j, +, 0}_k
-    /// The Remainder is the subscript of the next array dimension: [2i].
-    ///
-    /// The subscript of the outermost dimension is the Quotient: [j+k].
-    ///
-    /// Overall, we have: A[][n][m], and the access function: A[j+k][2i][5i].
-    void delinearize(ScalarEvolution &SE,
-                     SmallVectorImpl<const SCEV *> &Subscripts,
-                     SmallVectorImpl<const SCEV *> &Sizes,
-                     const SCEV *ElementSize) const;
   };
 
   //===--------------------------------------------------------------------===//

diff --git a/lib/Analysis/Delinearization.cpp b/lib/Analysis/Delinearization.cpp
index d603b7b21e310f525de37fbec65d83d7355691c1..9d157860326857cb5f8e49ee0b4183dd6c98ea88 100644 (file)
--- a/lib/Analysis/Delinearization.cpp
+++ b/lib/Analysis/Delinearization.cpp
@@ -115,7 +115,7 @@ void Delinearization::print(raw_ostream &O, const Module *) const {
       O << "AddRec: " << *AR << "\n";
 
       SmallVector<const SCEV *, 3> Subscripts, Sizes;
-      AR->delinearize(*SE, Subscripts, Sizes, SE->getElementSize(Inst));
+      SE->delinearize(AR, Subscripts, Sizes, SE->getElementSize(Inst));
       if (Subscripts.size() == 0 || Sizes.size() == 0 ||
           Subscripts.size() != Sizes.size()) {
         O << "failed to delinearize\n";

diff --git a/lib/Analysis/DependenceAnalysis.cpp b/lib/Analysis/DependenceAnalysis.cpp
index d9423cebcd9d9f7ff3d8fb48b6344a69cc81b868..4826ac407d7f0a58a51e9e4b811c1eb682d2853f 100644 (file)
--- a/lib/Analysis/DependenceAnalysis.cpp
+++ b/lib/Analysis/DependenceAnalysis.cpp
@@ -3266,8 +3266,8 @@ bool DependenceAnalysis::tryDelinearize(const SCEV *SrcSCEV,
 
   // First step: collect parametric terms in both array references.
   SmallVector<const SCEV *, 4> Terms;
-  SrcAR->collectParametricTerms(*SE, Terms);
-  DstAR->collectParametricTerms(*SE, Terms);
+  SE->collectParametricTerms(SrcAR, Terms);
+  SE->collectParametricTerms(DstAR, Terms);
 
   // Second step: find subscript sizes.
   SmallVector<const SCEV *, 4> Sizes;
@@ -3275,8 +3275,8 @@ bool DependenceAnalysis::tryDelinearize(const SCEV *SrcSCEV,
 
   // Third step: compute the access functions for each subscript.
   SmallVector<const SCEV *, 4> SrcSubscripts, DstSubscripts;
-  SrcAR->computeAccessFunctions(*SE, SrcSubscripts, Sizes);
-  DstAR->computeAccessFunctions(*SE, DstSubscripts, Sizes);
+  SE->computeAccessFunctions(SrcAR, SrcSubscripts, Sizes);
+  SE->computeAccessFunctions(DstAR, DstSubscripts, Sizes);
 
   // Fail when there is only a subscript: that's a linearized access function.
   if (SrcSubscripts.size() < 2 || DstSubscripts.size() < 2 ||

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 0e9f812c05e27cd34dd4009bd123e230af550ddc..9c7c1754e387acbc4a2dc8a539bf626084ee1b1f 100644 (file)
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -7647,11 +7647,11 @@ struct SCEVCollectTerms {
 }
 
 /// Find parametric terms in this SCEVAddRecExpr.
-void SCEVAddRecExpr::collectParametricTerms(
-    ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &Terms) const {
+void ScalarEvolution::collectParametricTerms(const SCEV *Expr,
+    SmallVectorImpl<const SCEV *> &Terms) {
   SmallVector<const SCEV *, 4> Strides;
-  SCEVCollectStrides StrideCollector(SE, Strides);
-  visitAll(this, StrideCollector);
+  SCEVCollectStrides StrideCollector(*this, Strides);
+  visitAll(Expr, StrideCollector);
 
   DEBUG({
       dbgs() << "Strides:\n";
@@ -7867,19 +7867,23 @@ void ScalarEvolution::findArrayDimensions(SmallVectorImpl<const SCEV *> &Terms,
 
 /// Third step of delinearization: compute the access functions for the
 /// Subscripts based on the dimensions in Sizes.
-void SCEVAddRecExpr::computeAccessFunctions(
-    ScalarEvolution &SE, SmallVectorImpl<const SCEV *> &Subscripts,
-    SmallVectorImpl<const SCEV *> &Sizes) const {
+void ScalarEvolution::computeAccessFunctions(
+    const SCEV *Expr, SmallVectorImpl<const SCEV *> &Subscripts,
+    SmallVectorImpl<const SCEV *> &Sizes) {
 
   // Early exit in case this SCEV is not an affine multivariate function.
-  if (Sizes.empty() || !this->isAffine())
+  if (Sizes.empty())
     return;
 
-  const SCEV *Res = this;
+  if (auto AR = dyn_cast<SCEVAddRecExpr>(Expr))
+    if (!AR->isAffine())
+      return;
+
+  const SCEV *Res = Expr;
   int Last = Sizes.size() - 1;
   for (int i = Last; i >= 0; i--) {
     const SCEV *Q, *R;
-    SCEVDivision::divide(SE, Res, Sizes[i], &Q, &R);
+    SCEVDivision::divide(*this, Res, Sizes[i], &Q, &R);
 
     DEBUG({
         dbgs() << "Res: " << *Res << "\n";
@@ -7971,31 +7975,31 @@ void SCEVAddRecExpr::computeAccessFunctions(
 /// asking for the SCEV of the memory access with respect to all enclosing
 /// loops, calling SCEV->delinearize on that and printing the results.
 
-void SCEVAddRecExpr::delinearize(ScalarEvolution &SE,
+void ScalarEvolution::delinearize(const SCEV *Expr,
                                  SmallVectorImpl<const SCEV *> &Subscripts,
                                  SmallVectorImpl<const SCEV *> &Sizes,
-                                 const SCEV *ElementSize) const {
+                                 const SCEV *ElementSize) {
   // First step: collect parametric terms.
   SmallVector<const SCEV *, 4> Terms;
-  collectParametricTerms(SE, Terms);
+  collectParametricTerms(Expr, Terms);
 
   if (Terms.empty())
     return;
 
   // Second step: find subscript sizes.
-  SE.findArrayDimensions(Terms, Sizes, ElementSize);
+  findArrayDimensions(Terms, Sizes, ElementSize);
 
   if (Sizes.empty())
     return;
 
   // Third step: compute the access functions for each subscript.
-  computeAccessFunctions(SE, Subscripts, Sizes);
+  computeAccessFunctions(Expr, Subscripts, Sizes);
 
   if (Subscripts.empty())
     return;
 
   DEBUG({
-      dbgs() << "succeeded to delinearize " << *this << "\n";
+      dbgs() << "succeeded to delinearize " << *Expr << "\n";
       dbgs() << "ArrayDecl[UnknownSize]";
       for (const SCEV *S : Sizes)
         dbgs() << "[" << *S << "]";