ScopInfo: Do not derive assumptions from all GEP pointer instructions

... but instead rely on the assumptions that we derive for load/store
instructions.

Before we were able to delinearize arrays, we used GEP pointer instructions
to derive information about the likely range of induction variables, which
gave us more freedom during loop scheduling. Today, this is not needed
any more as we delinearize multi-dimensional memory accesses and as part
of this process also "assume" that all accesses to these arrays remain
inbounds. The old derive-assumptions-from-GEP code has consequently become
mostly redundant. We drop it both to clean up our code, but also to improve
compile time. This change reduces the scop construction time for 3mm in
no-asserts mode on my machine from 48 to 37 ms.

llvm-svn: 280601

2 files changed, 0 insertions, 107 deletions

diff --git a/polly/include/polly/ScopInfo.h b/polly/include/polly/ScopInfo.h
index 2337021e595..cb8c48aff62 100644
--- a/polly/include/polly/ScopInfo.h
+++ b/polly/include/polly/ScopInfo.h
@@ -1193,38 +1193,6 @@ private:
                                 llvm::SmallVectorImpl<MemoryAccess *> &Loads);
   //@}
 
-  /// Derive assumptions about parameter values from GetElementPtrInst
-  ///
-  /// In case a GEP instruction references into a fixed size array e.g., an
-  /// access A[i][j] into an array A[100x100], LLVM-IR does not guarantee that
-  /// the subscripts always compute values that are within array bounds. In this
-  /// function we derive the set of parameter values for which all accesses are
-  /// within bounds and add the assumption that the scop is only every executed
-  /// with this set of parameter values.
-  ///
-  /// Example:
-  ///
-  ///   void foo(float A[][20], long n, long m {
-  ///     for (long i = 0; i < n; i++)
-  ///       for (long j = 0; j < m; j++)
-  ///         A[i][j] = ...
-  ///
-  /// This loop yields out-of-bound accesses if m is at least 20 and at the same
-  /// time at least one iteration of the outer loop is executed. Hence, we
-  /// assume:
-  ///
-  ///   n <= 0 or m <= 20.
-  ///
-  /// TODO: The location where the GEP instruction is executed is not
-  /// necessarily the location where the memory is actually accessed. As a
-  /// result scanning for GEP[s] is imprecise. Even though this is not a
-  /// correctness problem, this imprecision may result in missed optimizations
-  /// or non-optimal run-time checks.
-  void deriveAssumptionsFromGEP(GetElementPtrInst *Inst, LoopInfo &LI);
-
-  /// Derive assumptions about parameter values.
-  void deriveAssumptions(LoopInfo &LI);
-
 public:
   ~ScopStmt();
 
diff --git a/polly/lib/Analysis/ScopInfo.cpp b/polly/lib/Analysis/ScopInfo.cpp
index 61edeaf2841..ee5e94ae826 100644
--- a/polly/lib/Analysis/ScopInfo.cpp
+++ b/polly/lib/Analysis/ScopInfo.cpp
@@ -1397,79 +1397,6 @@ void ScopStmt::buildDomain() {
   Domain = isl_set_set_tuple_id(Domain, Id);
 }
 
-void ScopStmt::deriveAssumptionsFromGEP(GetElementPtrInst *GEP, LoopInfo &LI) {
-  isl_ctx *Ctx = Parent.getIslCtx();
-  isl_local_space *LSpace = isl_local_space_from_space(getDomainSpace());
-  ScalarEvolution &SE = *Parent.getSE();
-
-  // The set of loads that are required to be invariant.
-  auto &ScopRIL = Parent.getRequiredInvariantLoads();
-
-  std::vector<const SCEV *> Subscripts;
-  std::vector<int> Sizes;
-
-  std::tie(Subscripts, Sizes) = getIndexExpressionsFromGEP(GEP, SE);
-
-  int IndexOffset = Subscripts.size() - Sizes.size();
-
-  assert(IndexOffset <= 1 && "Unexpected large index offset");
-
-  auto *NotExecuted = isl_set_complement(isl_set_params(getDomain()));
-  for (size_t i = 0; i < Sizes.size(); i++) {
-    auto *Expr = Subscripts[i + IndexOffset];
-    auto Size = Sizes[i];
-
-    auto *Scope = LI.getLoopFor(getEntryBlock());
-    InvariantLoadsSetTy AccessILS;
-    if (!isAffineExpr(&Parent.getRegion(), Scope, Expr, SE, &AccessILS))
-      continue;
-
-    bool NonAffine = false;
-    for (LoadInst *LInst : AccessILS)
-      if (!ScopRIL.count(LInst))
-        NonAffine = true;
-
-    if (NonAffine)
-      continue;
-
-    isl_pw_aff *AccessOffset = getPwAff(Expr);
-    AccessOffset =
-        isl_pw_aff_set_tuple_id(AccessOffset, isl_dim_in, getDomainId());
-
-    isl_pw_aff *DimSize = isl_pw_aff_from_aff(isl_aff_val_on_domain(
-        isl_local_space_copy(LSpace), isl_val_int_from_si(Ctx, Size)));
-
-    isl_set *OutOfBound = isl_pw_aff_ge_set(AccessOffset, DimSize);
-    OutOfBound = isl_set_intersect(getDomain(), OutOfBound);
-    OutOfBound = isl_set_params(OutOfBound);
-    isl_set *InBound = isl_set_complement(OutOfBound);
-
-    // A => B == !A or B
-    isl_set *InBoundIfExecuted =
-        isl_set_union(isl_set_copy(NotExecuted), InBound);
-
-    InBoundIfExecuted = isl_set_coalesce(InBoundIfExecuted);
-    Parent.recordAssumption(INBOUNDS, InBoundIfExecuted, GEP->getDebugLoc(),
-                            AS_ASSUMPTION);
-  }
-
-  isl_local_space_free(LSpace);
-  isl_set_free(NotExecuted);
-}
-
-void ScopStmt::deriveAssumptions(LoopInfo &LI) {
-  for (auto *MA : *this) {
-    if (!MA->isArrayKind())
-      continue;
-
-    MemAccInst Acc(MA->getAccessInstruction());
-    auto *GEP = dyn_cast_or_null<GetElementPtrInst>(Acc.getPointerOperand());
-
-    if (GEP)
-      deriveAssumptionsFromGEP(GEP, LI);
-  }
-}
-
 void ScopStmt::collectSurroundingLoops() {
   for (unsigned u = 0, e = isl_set_n_dim(Domain); u < e; u++) {
     isl_id *DimId = isl_set_get_dim_id(Domain, isl_dim_set, u);
@@ -1499,8 +1426,6 @@ void ScopStmt::init(LoopInfo &LI) {
   collectSurroundingLoops();
   buildAccessRelations();
 
-  deriveAssumptions(LI);
-
   if (DetectReductions)
     checkForReductions();
 }