Add caching to the SCEVAffinator

  While the compile time is not affected by this patch much it will
  allow us to look at all translated expressions after the SCoP is build
  in a convenient way. Additionally, bigger SCoPs or SCoPs with
  repeating complicated expressions might benefit from the cache later
  on.

Reviewers: grosser, Meinersbur

Subscribers: #polly

Differential Revision: http://reviews.llvm.org/D11975

llvm-svn: 244734

diff --git a/polly/include/polly/Support/SCEVAffinator.h b/polly/include/polly/Support/SCEVAffinator.h
index bc2a273..edc3522 100644 (file)
--- a/polly/include/polly/Support/SCEVAffinator.h
+++ b/polly/include/polly/Support/SCEVAffinator.h
@@ -14,6 +14,7 @@
 #ifndef POLLY_SCEV_AFFINATOR_H
 #define POLLY_SCEV_AFFINATOR_H
 
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 
 #include "isl/ctx.h"
@@ -44,6 +45,7 @@ class ScopStmt;
 struct SCEVAffinator : public llvm::SCEVVisitor<SCEVAffinator, isl_pw_aff *> {
 public:
   SCEVAffinator(Scop *S);
+  ~SCEVAffinator();
 
   /// @brief Translate a SCEV to an isl_pw_aff.
   ///
@@ -54,11 +56,18 @@ public:
   __isl_give isl_pw_aff *getPwAff(const llvm::SCEV *E, const ScopStmt *Stmt);
 
 private:
+  /// @brief Key to identify cached expressions.
+  using CacheKey = std::pair<const llvm::SCEV *, const ScopStmt *>;
+
+  /// @brief Map to remembered cached expressions.
+  llvm::DenseMap<CacheKey, isl_pw_aff *> CachedExpressions;
+
   Scop *S;
   isl_ctx *Ctx;
   unsigned NumIterators;
   const llvm::Region &R;
   llvm::ScalarEvolution &SE;
+  const ScopStmt *Stmt;
 
   int getLoopDepth(const llvm::Loop *L);
 

diff --git a/polly/lib/Support/SCEVAffinator.cpp b/polly/lib/Support/SCEVAffinator.cpp
index 7bdc69d..1ac01e0 100644 (file)
--- a/polly/lib/Support/SCEVAffinator.cpp
+++ b/polly/lib/Support/SCEVAffinator.cpp
@@ -29,8 +29,14 @@ using namespace polly;
 SCEVAffinator::SCEVAffinator(Scop *S)
     : S(S), Ctx(S->getIslCtx()), R(S->getRegion()), SE(*S->getSE()) {}
 
+SCEVAffinator::~SCEVAffinator() {
+  for (const auto &CachedPair : CachedExpressions)
+    isl_pw_aff_free(CachedPair.second);
+}
+
 __isl_give isl_pw_aff *SCEVAffinator::getPwAff(const SCEV *Expr,
                                                const ScopStmt *Stmt) {
+  this->Stmt = Stmt;
   NumIterators = Stmt->getNumIterators();
 
   S->addParams(getParamsInAffineExpr(&R, Expr, SE));
@@ -39,6 +45,13 @@ __isl_give isl_pw_aff *SCEVAffinator::getPwAff(const SCEV *Expr,
 }
 
 __isl_give isl_pw_aff *SCEVAffinator::visit(const SCEV *Expr) {
+
+  auto Key = std::make_pair(Expr, Stmt);
+  isl_pw_aff *PWA = CachedExpressions[Key];
+
+  if (PWA)
+    return isl_pw_aff_copy(PWA);
+
   // In case the scev is a valid parameter, we do not further analyze this
   // expression, but create a new parameter in the isl_pw_aff. This allows us
   // to treat subexpressions that we cannot translate into an piecewise affine
@@ -51,10 +64,14 @@ __isl_give isl_pw_aff *SCEVAffinator::visit(const SCEV *Expr) {
     isl_aff *Affine = isl_aff_zero_on_domain(isl_local_space_from_space(Space));
     Affine = isl_aff_add_coefficient_si(Affine, isl_dim_param, 0, 1);
 
-    return isl_pw_aff_alloc(Domain, Affine);
+    PWA = isl_pw_aff_alloc(Domain, Affine);
+    CachedExpressions[Key] = PWA;
+    return isl_pw_aff_copy(PWA);
   }
 
-  return SCEVVisitor<SCEVAffinator, isl_pw_aff *>::visit(Expr);
+  PWA = SCEVVisitor<SCEVAffinator, isl_pw_aff *>::visit(Expr);
+  CachedExpressions[Key] = PWA;
+  return isl_pw_aff_copy(PWA);
 }
 
 __isl_give isl_pw_aff *SCEVAffinator::visitConstant(const SCEVConstant *Expr) {