[DA] remove Constraints class

[sebpop]

This is to be committed on top of #167698

[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: Sebastian Pop (sebpop)

Changes

This is to be committed on top of #167698

---

Patch is 49.25 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/168963.diff

6 Files Affected:

• (modified) llvm/include/llvm/Analysis/DependenceAnalysis.h (+6-184)
• (modified) llvm/lib/Analysis/DependenceAnalysis.cpp (+28-574)
• (modified) llvm/test/Analysis/DependenceAnalysis/Propagating.ll (+1-1)
• (modified) llvm/test/Analysis/DependenceAnalysis/SymbolicSIV.ll (+1-1)
• (modified) llvm/test/Analysis/DependenceAnalysis/WeakCrossingSIV.ll (+2-2)
• (modified) llvm/test/Analysis/DependenceAnalysis/run-specific-dependence-test.ll (+2-2)

diff --git a/llvm/include/llvm/Analysis/DependenceAnalysis.h b/llvm/include/llvm/Analysis/DependenceAnalysis.h
index 85c9af4fffcde..2e845104464a5 100644
--- a/llvm/include/llvm/Analysis/DependenceAnalysis.h
+++ b/llvm/include/llvm/Analysis/DependenceAnalysis.h
@@ -365,48 +365,6 @@ class DependenceInfo {
   depends(Instruction *Src, Instruction *Dst,
           bool UnderRuntimeAssumptions = false);
 
-  /// getSplitIteration - Give a dependence that's splittable at some
-  /// particular level, return the iteration that should be used to split
-  /// the loop.
-  ///
-  /// Generally, the dependence analyzer will be used to build
-  /// a dependence graph for a function (basically a map from instructions
-  /// to dependences). Looking for cycles in the graph shows us loops
-  /// that cannot be trivially vectorized/parallelized.
-  ///
-  /// We can try to improve the situation by examining all the dependences
-  /// that make up the cycle, looking for ones we can break.
-  /// Sometimes, peeling the first or last iteration of a loop will break
-  /// dependences, and there are flags for those possibilities.
-  /// Sometimes, splitting a loop at some other iteration will do the trick,
-  /// and we've got a flag for that case. Rather than waste the space to
-  /// record the exact iteration (since we rarely know), we provide
-  /// a method that calculates the iteration. It's a drag that it must work
-  /// from scratch, but wonderful in that it's possible.
-  ///
-  /// Here's an example:
-  ///
-  ///    for (i = 0; i < 10; i++)
-  ///        A[i] = ...
-  ///        ... = A[11 - i]
-  ///
-  /// There's a loop-carried flow dependence from the store to the load,
-  /// found by the weak-crossing SIV test. The dependence will have a flag,
-  /// indicating that the dependence can be broken by splitting the loop.
-  /// Calling getSplitIteration will return 5.
-  /// Splitting the loop breaks the dependence, like so:
-  ///
-  ///    for (i = 0; i <= 5; i++)
-  ///        A[i] = ...
-  ///        ... = A[11 - i]
-  ///    for (i = 6; i < 10; i++)
-  ///        A[i] = ...
-  ///        ... = A[11 - i]
-  ///
-  /// breaks the dependence and allows us to vectorize/parallelize
-  /// both loops.
-  LLVM_ABI const SCEV *getSplitIteration(const Dependence &Dep, unsigned Level);
-
   Function *getFunction() const { return F; }
 
   /// getRuntimeAssumptions - Returns all the runtime assumptions under which
@@ -447,106 +405,6 @@ class DependenceInfo {
     unsigned char DirSet;
   };
 
-  /// Constraint - This private class represents a constraint, as defined
-  /// in the paper
-  ///
-  ///           Practical Dependence Testing
-  ///           Goff, Kennedy, Tseng
-  ///           PLDI 1991
-  ///
-  /// There are 5 kinds of constraint, in a hierarchy.
-  ///   1) Any - indicates no constraint, any dependence is possible.
-  ///   2) Line - A line ax + by = c, where a, b, and c are parameters,
-  ///             representing the dependence equation.
-  ///   3) Distance - The value d of the dependence distance;
-  ///   4) Point - A point <x, y> representing the dependence from
-  ///              iteration x to iteration y.
-  ///   5) Empty - No dependence is possible.
-  class Constraint {
-  private:
-    enum ConstraintKind { Empty, Point, Distance, Line, Any } Kind;
-    ScalarEvolution *SE;
-    const SCEV *A;
-    const SCEV *B;
-    const SCEV *C;
-    const Loop *AssociatedSrcLoop;
-    const Loop *AssociatedDstLoop;
-
-  public:
-    /// isEmpty - Return true if the constraint is of kind Empty.
-    bool isEmpty() const { return Kind == Empty; }
-
-    /// isPoint - Return true if the constraint is of kind Point.
-    bool isPoint() const { return Kind == Point; }
-
-    /// isDistance - Return true if the constraint is of kind Distance.
-    bool isDistance() const { return Kind == Distance; }
-
-    /// isLine - Return true if the constraint is of kind Line.
-    /// Since Distance's can also be represented as Lines, we also return
-    /// true if the constraint is of kind Distance.
-    bool isLine() const { return Kind == Line || Kind == Distance; }
-
-    /// isAny - Return true if the constraint is of kind Any;
-    bool isAny() const { return Kind == Any; }
-
-    /// getX - If constraint is a point <X, Y>, returns X.
-    /// Otherwise assert.
-    LLVM_ABI const SCEV *getX() const;
-
-    /// getY - If constraint is a point <X, Y>, returns Y.
-    /// Otherwise assert.
-    LLVM_ABI const SCEV *getY() const;
-
-    /// getA - If constraint is a line AX + BY = C, returns A.
-    /// Otherwise assert.
-    LLVM_ABI const SCEV *getA() const;
-
-    /// getB - If constraint is a line AX + BY = C, returns B.
-    /// Otherwise assert.
-    LLVM_ABI const SCEV *getB() const;
-
-    /// getC - If constraint is a line AX + BY = C, returns C.
-    /// Otherwise assert.
-    LLVM_ABI const SCEV *getC() const;
-
-    /// getD - If constraint is a distance, returns D.
-    /// Otherwise assert.
-    LLVM_ABI const SCEV *getD() const;
-
-    /// getAssociatedSrcLoop - Returns the source loop associated with this
-    /// constraint.
-    LLVM_ABI const Loop *getAssociatedSrcLoop() const;
-
-    /// getAssociatedDstLoop - Returns the destination loop associated with
-    /// this constraint.
-    LLVM_ABI const Loop *getAssociatedDstLoop() const;
-
-    /// setPoint - Change a constraint to Point.
-    LLVM_ABI void setPoint(const SCEV *X, const SCEV *Y,
-                           const Loop *CurrentSrcLoop,
-                           const Loop *CurrentDstLoop);
-
-    /// setLine - Change a constraint to Line.
-    LLVM_ABI void setLine(const SCEV *A, const SCEV *B, const SCEV *C,
-                          const Loop *CurrentSrcLoop,
-                          const Loop *CurrentDstLoop);
-
-    /// setDistance - Change a constraint to Distance.
-    LLVM_ABI void setDistance(const SCEV *D, const Loop *CurrentSrcLoop,
-                              const Loop *CurrentDstLoop);
-
-    /// setEmpty - Change a constraint to Empty.
-    LLVM_ABI void setEmpty();
-
-    /// setAny - Change a constraint to Any.
-    LLVM_ABI void setAny(ScalarEvolution *SE);
-
-    /// dump - For debugging purposes. Dumps the constraint
-    /// out to OS.
-    LLVM_ABI void dump(raw_ostream &OS) const;
-  };
-
   /// Returns true if two loops have the Same iteration Space and Depth. To be
   /// more specific, two loops have SameSD if they are in the same nesting
   /// depth and have the same backedge count. SameSD stands for Same iteration
@@ -713,8 +571,7 @@ class DependenceInfo {
   /// If the dependence isn't proven to exist,
   /// marks the Result as inconsistent.
   bool testSIV(const SCEV *Src, const SCEV *Dst, unsigned &Level,
-               FullDependence &Result, Constraint &NewConstraint,
-               const SCEV *&SplitIter) const;
+               FullDependence &Result) const;
 
   /// testRDIV - Tests the RDIV subscript pair (Src and Dst) for dependence.
   /// Things of the form [c1 + a1*i] and [c2 + a2*j]
@@ -744,7 +601,7 @@ class DependenceInfo {
   bool strongSIVtest(const SCEV *Coeff, const SCEV *SrcConst,
                      const SCEV *DstConst, const Loop *CurrentSrcLoop,
                      const Loop *CurrentDstLoop, unsigned Level,
-                     FullDependence &Result, Constraint &NewConstraint) const;
+                     FullDependence &Result) const;
 
   /// weakCrossingSIVtest - Tests the weak-crossing SIV subscript pair
   /// (Src and Dst) for dependence.
@@ -759,8 +616,7 @@ class DependenceInfo {
   bool weakCrossingSIVtest(const SCEV *SrcCoeff, const SCEV *SrcConst,
                            const SCEV *DstConst, const Loop *CurrentSrcLoop,
                            const Loop *CurrentDstLoop, unsigned Level,
-                           FullDependence &Result, Constraint &NewConstraint,
-                           const SCEV *&SplitIter) const;
+                           FullDependence &Result) const;
 
   /// ExactSIVtest - Tests the SIV subscript pair
   /// (Src and Dst) for dependence.
@@ -774,8 +630,7 @@ class DependenceInfo {
   bool exactSIVtest(const SCEV *SrcCoeff, const SCEV *DstCoeff,
                     const SCEV *SrcConst, const SCEV *DstConst,
                     const Loop *CurrentSrcLoop, const Loop *CurrentDstLoop,
-                    unsigned Level, FullDependence &Result,
-                    Constraint &NewConstraint) const;
+                    unsigned Level, FullDependence &Result) const;
 
   /// weakZeroSrcSIVtest - Tests the weak-zero SIV subscript pair
   /// (Src and Dst) for dependence.
@@ -790,8 +645,7 @@ class DependenceInfo {
   bool weakZeroSrcSIVtest(const SCEV *DstCoeff, const SCEV *SrcConst,
                           const SCEV *DstConst, const Loop *CurrentSrcLoop,
                           const Loop *CurrentDstLoop, unsigned Level,
-                          FullDependence &Result,
-                          Constraint &NewConstraint) const;
+                          FullDependence &Result) const;
 
   /// weakZeroDstSIVtest - Tests the weak-zero SIV subscript pair
   /// (Src and Dst) for dependence.
@@ -806,8 +660,7 @@ class DependenceInfo {
   bool weakZeroDstSIVtest(const SCEV *SrcCoeff, const SCEV *SrcConst,
                           const SCEV *DstConst, const Loop *CurrentSrcLoop,
                           const Loop *CurrentDstLoop, unsigned Level,
-                          FullDependence &Result,
-                          Constraint &NewConstraint) const;
+                          FullDependence &Result) const;
 
   /// exactRDIVtest - Tests the RDIV subscript pair for dependence.
   /// Things of the form [c1 + a*i] and [c2 + b*j],
@@ -927,37 +780,6 @@ class DependenceInfo {
   void findBoundsEQ(CoefficientInfo *A, CoefficientInfo *B, BoundInfo *Bound,
                     unsigned K) const;
 
-  /// intersectConstraints - Updates X with the intersection
-  /// of the Constraints X and Y. Returns true if X has changed.
-  bool intersectConstraints(Constraint *X, const Constraint *Y);
-
-  /// findCoefficient - Given a linear SCEV,
-  /// return the coefficient corresponding to specified loop.
-  /// If there isn't one, return the SCEV constant 0.
-  /// For example, given a*i + b*j + c*k, returning the coefficient
-  /// corresponding to the j loop would yield b.
-  const SCEV *findCoefficient(const SCEV *Expr, const Loop *TargetLoop) const;
-
-  /// zeroCoefficient - Given a linear SCEV,
-  /// return the SCEV given by zeroing out the coefficient
-  /// corresponding to the specified loop.
-  /// For example, given a*i + b*j + c*k, zeroing the coefficient
-  /// corresponding to the j loop would yield a*i + c*k.
-  const SCEV *zeroCoefficient(const SCEV *Expr, const Loop *TargetLoop) const;
-
-  /// addToCoefficient - Given a linear SCEV Expr,
-  /// return the SCEV given by adding some Value to the
-  /// coefficient corresponding to the specified TargetLoop.
-  /// For example, given a*i + b*j + c*k, adding 1 to the coefficient
-  /// corresponding to the j loop would yield a*i + (b+1)*j + c*k.
-  const SCEV *addToCoefficient(const SCEV *Expr, const Loop *TargetLoop,
-                               const SCEV *Value) const;
-
-  /// updateDirection - Update direction vector entry
-  /// based on the current constraint.
-  void updateDirection(Dependence::DVEntry &Level,
-                       const Constraint &CurConstraint) const;
-
   /// Given a linear access function, tries to recover subscripts
   /// for each dimension of the array element access.
   bool tryDelinearize(Instruction *Src, Instruction *Dst,
diff --git a/llvm/lib/Analysis/DependenceAnalysis.cpp b/llvm/lib/Analysis/DependenceAnalysis.cpp
index ea261820fb2e6..940cedea33def 100644
--- a/llvm/lib/Analysis/DependenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DependenceAnalysis.cpp
@@ -18,11 +18,6 @@
 // of memory references in a function, returning either NULL, for no dependence,
 // or a more-or-less detailed description of the dependence between them.
 //
-// Currently, the implementation cannot propagate constraints between
-// coupled RDIV subscripts and lacks a multi-subscript MIV test.
-// Both of these are conservative weaknesses;
-// that is, not a source of correctness problems.
-//
 // Since Clang linearizes some array subscripts, the dependence
 // analysis is using SCEV->delinearize to recover the representation of multiple
 // subscripts, and thus avoid the more expensive and less precise MIV tests. The
@@ -92,8 +87,6 @@ STATISTIC(ExactRDIVapplications, "Exact RDIV applications");
 STATISTIC(ExactRDIVindependence, "Exact RDIV independence");
 STATISTIC(SymbolicRDIVapplications, "Symbolic RDIV applications");
 STATISTIC(SymbolicRDIVindependence, "Symbolic RDIV independence");
-STATISTIC(DeltaApplications, "Delta applications");
-STATISTIC(DeltaSuccesses, "Delta successes");
 STATISTIC(GCDapplications, "GCD applications");
 STATISTIC(GCDsuccesses, "GCD successes");
 STATISTIC(GCDindependence, "GCD independence");
@@ -445,7 +438,6 @@ static void dumpExampleDependence(raw_ostream &OS, DependenceInfo *DA,
             for (unsigned Level = 1; Level <= D->getLevels(); Level++) {
               if (D->isSplitable(Level)) {
                 OS << "  da analyze - split level = " << Level;
-                OS << ", iteration = " << *DA->getSplitIteration(*D, Level);
                 OS << "!\n";
               }
             }
@@ -625,282 +617,6 @@ bool FullDependence::inSameSDLoops(unsigned Level) const {
   return Level > Levels;
 }
 
-//===----------------------------------------------------------------------===//
-// DependenceInfo::Constraint methods
-
-// If constraint is a point <X, Y>, returns X.
-// Otherwise assert.
-const SCEV *DependenceInfo::Constraint::getX() const {
-  assert(Kind == Point && "Kind should be Point");
-  return A;
-}
-
-// If constraint is a point <X, Y>, returns Y.
-// Otherwise assert.
-const SCEV *DependenceInfo::Constraint::getY() const {
-  assert(Kind == Point && "Kind should be Point");
-  return B;
-}
-
-// If constraint is a line AX + BY = C, returns A.
-// Otherwise assert.
-const SCEV *DependenceInfo::Constraint::getA() const {
-  assert((Kind == Line || Kind == Distance) &&
-         "Kind should be Line (or Distance)");
-  return A;
-}
-
-// If constraint is a line AX + BY = C, returns B.
-// Otherwise assert.
-const SCEV *DependenceInfo::Constraint::getB() const {
-  assert((Kind == Line || Kind == Distance) &&
-         "Kind should be Line (or Distance)");
-  return B;
-}
-
-// If constraint is a line AX + BY = C, returns C.
-// Otherwise assert.
-const SCEV *DependenceInfo::Constraint::getC() const {
-  assert((Kind == Line || Kind == Distance) &&
-         "Kind should be Line (or Distance)");
-  return C;
-}
-
-// If constraint is a distance, returns D.
-// Otherwise assert.
-const SCEV *DependenceInfo::Constraint::getD() const {
-  assert(Kind == Distance && "Kind should be Distance");
-  return SE->getNegativeSCEV(C);
-}
-
-// Returns the source loop associated with this constraint.
-const Loop *DependenceInfo::Constraint::getAssociatedSrcLoop() const {
-  assert((Kind == Distance || Kind == Line || Kind == Point) &&
-         "Kind should be Distance, Line, or Point");
-  return AssociatedSrcLoop;
-}
-
-// Returns the destination loop associated with this constraint.
-const Loop *DependenceInfo::Constraint::getAssociatedDstLoop() const {
-  assert((Kind == Distance || Kind == Line || Kind == Point) &&
-         "Kind should be Distance, Line, or Point");
-  return AssociatedDstLoop;
-}
-
-void DependenceInfo::Constraint::setPoint(const SCEV *X, const SCEV *Y,
-                                          const Loop *CurSrcLoop,
-                                          const Loop *CurDstLoop) {
-  Kind = Point;
-  A = X;
-  B = Y;
-  AssociatedSrcLoop = CurSrcLoop;
-  AssociatedDstLoop = CurDstLoop;
-}
-
-void DependenceInfo::Constraint::setLine(const SCEV *AA, const SCEV *BB,
-                                         const SCEV *CC, const Loop *CurSrcLoop,
-                                         const Loop *CurDstLoop) {
-  Kind = Line;
-  A = AA;
-  B = BB;
-  C = CC;
-  AssociatedSrcLoop = CurSrcLoop;
-  AssociatedDstLoop = CurDstLoop;
-}
-
-void DependenceInfo::Constraint::setDistance(const SCEV *D,
-                                             const Loop *CurSrcLoop,
-                                             const Loop *CurDstLoop) {
-  Kind = Distance;
-  A = SE->getOne(D->getType());
-  B = SE->getNegativeSCEV(A);
-  C = SE->getNegativeSCEV(D);
-  AssociatedSrcLoop = CurSrcLoop;
-  AssociatedDstLoop = CurDstLoop;
-}
-
-void DependenceInfo::Constraint::setEmpty() { Kind = Empty; }
-
-void DependenceInfo::Constraint::setAny(ScalarEvolution *NewSE) {
-  SE = NewSE;
-  Kind = Any;
-}
-
-#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
-// For debugging purposes. Dumps the constraint out to OS.
-LLVM_DUMP_METHOD void DependenceInfo::Constraint::dump(raw_ostream &OS) const {
-  if (isEmpty())
-    OS << " Empty\n";
-  else if (isAny())
-    OS << " Any\n";
-  else if (isPoint())
-    OS << " Point is <" << *getX() << ", " << *getY() << ">\n";
-  else if (isDistance())
-    OS << " Distance is " << *getD() << " (" << *getA() << "*X + " << *getB()
-       << "*Y = " << *getC() << ")\n";
-  else if (isLine())
-    OS << " Line is " << *getA() << "*X + " << *getB() << "*Y = " << *getC()
-       << "\n";
-  else
-    llvm_unreachable("unknown constraint type in Constraint::dump");
-}
-#endif
-
-// Updates X with the intersection
-// of the Constraints X and Y. Returns true if X has changed.
-// Corresponds to Figure 4 from the paper
-//
-//            Practical Dependence Testing
-//            Goff, Kennedy, Tseng
-//            PLDI 1991
-bool DependenceInfo::intersectConstraints(Constraint *X, const Constraint *Y) {
-  ++DeltaApplications;
-  LLVM_DEBUG(dbgs() << "\tintersect constraints\n");
-  LLVM_DEBUG(dbgs() << "\t    X ="; X->dump(dbgs()));
-  LLVM_DEBUG(dbgs() << "\t    Y ="; Y->dump(dbgs()));
-  assert(!Y->isPoint() && "Y must not be a Point");
-  if (X->isAny()) {
-    if (Y->isAny())
-      return false;
-    *X = *Y;
-    return true;
-  }
-  if (X->isEmpty())
-    return false;
-  if (Y->isEmpty()) {
-    X->setEmpty();
-    return true;
-  }
-
-  if (X->isDistance() && Y->isDistance()) {
-    LLVM_DEBUG(dbgs() << "\t    intersect 2 distances\n");
-    if (isKnownPredicate(CmpInst::ICMP_EQ, X->getD(), Y->getD()))
-      return false;
-    if (isKnownPredicate(CmpInst::ICMP_NE, X->getD(), Y->getD())) {
-      X->setEmpty();
-      ++DeltaSuccesses;
-      return true;
-    }
-    // Hmmm, interesting situation.
-    // I guess if either is constant, keep it and ignore the other.
-    if (isa<SCEVConstant>(Y->getD())) {
-      *X = *Y;
-      return true;
-    }
-    return false;
-  }
-
-  // At this point, the pseudo-code in Figure 4 of the paper
-  // checks if (X->isPoint() && Y->isPoint()).
-  // This case can't occur in our implementation,
-  // since a Point can only arise as the result of intersecting
-  // two Line constraints, and the right-hand value, Y, is never
-  // the result of an intersection.
-  assert(!(X->isPoint() && Y->isPoint()) &&
-         "We shouldn't ever see X->isPoint() && Y->isPoint()");
-
-  if (X->isLine() && Y->isLine()) {
-    LLVM_DEBUG(dbgs() << "\t    intersect 2 lines\n");
-    const SCEV *Prod1 = SE->getMulExpr(X->getA(), Y->getB());
-    const SCEV *Prod2 = SE->getMulExpr(X->getB(), Y->getA());
-    if (isKnownPredicate(CmpInst::ICMP_EQ, Prod1, Prod2)) {
-      // slopes are equal, so lines are parallel
-      LLVM_DEBUG(dbgs() << "\t\tsame slope\n");
-      Prod1 = SE->getMulExpr(X->getC(), Y->getB());
-      Prod2 = SE->getMulExpr(X->getB(), Y->getC());
-      if (isKnownPredicate(CmpInst::ICMP_EQ, Prod1, Prod2))
-        return false;
-      if (isKnownPredicate(CmpInst::ICMP_NE, Prod1, Prod2)) {
-        X->setEmpty();
-        ++DeltaSuccesses;
-        return true;
-      }
-      return false;
-    }
-    if (isKnownPredicate(CmpInst::ICMP_NE, Prod1, Prod2)) {
-      // slopes differ, so lines intersect
-      LLVM_DEBUG(dbgs() << "\t\tdifferent slopes\n");
-      const SCEV *C1B2 = SE->getMulExpr(X->getC(), Y->getB());
-      const SCEV *C1A2 = SE->getMulExpr(X->getC(), Y->getA());
-      const SCEV *C2B1 = SE->getMulExpr(Y->getC(), X->getB());
-      const SCEV *C2A1 = SE->getMulExpr(Y->getC(), X->g...
[truncated]

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