Revert "[OpenMP] Avoid VLAs for some reductions on array sections"

This breaks at least two buildbots:
http://lab.llvm.org:8011/builders/clang-cmake-x86_64-avx2-linux/builds/1175
http://lab.llvm.org:8011/builders/clang-atom-d525-fedora-rel/builds/10478

This reverts commit r316229 during local investigation.

llvm-svn: 316235

3 files changed, 9 insertions, 91 deletions

diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index 3396c63cd62..f98ff85565f 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -925,7 +925,7 @@ void ReductionCodeGen::emitAggregateType(CodeGenFunction &CGF, unsigned N) {
       cast<VarDecl>(cast<DeclRefExpr>(ClausesData[N].Private)->getDecl());
   QualType PrivateType = PrivateVD->getType();
   bool AsArraySection = isa<OMPArraySectionExpr>(ClausesData[N].Ref);
-  if (!PrivateType->isVariablyModifiedType()) {
+  if (!AsArraySection && !PrivateType->isVariablyModifiedType()) {
     Sizes.emplace_back(
         CGF.getTypeSize(
             SharedAddresses[N].first.getType().getNonReferenceType()),
@@ -963,9 +963,10 @@ void ReductionCodeGen::emitAggregateType(CodeGenFunction &CGF, unsigned N,
   auto *PrivateVD =
       cast<VarDecl>(cast<DeclRefExpr>(ClausesData[N].Private)->getDecl());
   QualType PrivateType = PrivateVD->getType();
-  if (!PrivateType->isVariablyModifiedType()) {
+  bool AsArraySection = isa<OMPArraySectionExpr>(ClausesData[N].Ref);
+  if (!AsArraySection && !PrivateType->isVariablyModifiedType()) {
     assert(!Size && !Sizes[N].second &&
-           "Size should be nullptr for non-variably modified reduction "
+           "Size should be nullptr for non-variably modified redution "
            "items.");
     return;
   }
@@ -993,7 +994,8 @@ void ReductionCodeGen::emitInitialization(
                                        CGF.ConvertTypeForMem(SharedType)),
       SharedType, SharedAddresses[N].first.getBaseInfo(),
       CGF.CGM.getTBAAAccessInfo(SharedType));
-  if (CGF.getContext().getAsArrayType(PrivateVD->getType())) {
+  if (isa<OMPArraySectionExpr>(ClausesData[N].Ref) ||
+      CGF.getContext().getAsArrayType(PrivateVD->getType())) {
     emitAggregateInitialization(CGF, N, PrivateAddr, SharedLVal, DRD);
   } else if (DRD && (DRD->getInitializer() || !PrivateVD->hasInit())) {
     emitInitWithReductionInitializer(CGF, DRD, ClausesData[N].ReductionOp,
diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index 0e5ea798ebd..cdec3e35f97 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -996,9 +996,7 @@ void CodeGenFunction::EmitOMPReductionClauseInit(
 
     auto *LHSVD = cast<VarDecl>(cast<DeclRefExpr>(*ILHS)->getDecl());
     auto *RHSVD = cast<VarDecl>(cast<DeclRefExpr>(*IRHS)->getDecl());
-    QualType Type = PrivateVD->getType();
-    bool isaOMPArraySectionExpr = isa<OMPArraySectionExpr>(IRef);
-    if (isaOMPArraySectionExpr && Type->isVariablyModifiedType()) {
+    if (isa<OMPArraySectionExpr>(IRef)) {
       // Store the address of the original variable associated with the LHS
       // implicit variable.
       PrivateScope.addPrivate(LHSVD, [&RedCG, Count]() -> Address {
@@ -1007,8 +1005,7 @@ void CodeGenFunction::EmitOMPReductionClauseInit(
       PrivateScope.addPrivate(RHSVD, [this, PrivateVD]() -> Address {
         return GetAddrOfLocalVar(PrivateVD);
       });
-    } else if ((isaOMPArraySectionExpr && Type->isScalarType()) ||
-               isa<ArraySubscriptExpr>(IRef)) {
+    } else if (isa<ArraySubscriptExpr>(IRef)) {
       // Store the address of the original variable associated with the LHS
       // implicit variable.
       PrivateScope.addPrivate(LHSVD, [&RedCG, Count]() -> Address {
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index bf89eb0b2f2..a024888fbf0 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -9330,68 +9330,6 @@ struct ReductionData {
 };
 } // namespace
 
-static bool CheckOMPArraySectionConstantForReduction(
-    ASTContext &Context, const OMPArraySectionExpr *OASE, bool &SingleElement,
-    SmallVectorImpl<llvm::APSInt> &ArraySizes) {
-  const Expr *Length = OASE->getLength();
-  if (Length == nullptr) {
-    // For array sections of the form [1:] or [:], we would need to analyze
-    // the lower bound...
-    if (OASE->getColonLoc().isValid())
-      return false;
-
-    // This is an array subscript which has implicit length 1!
-    SingleElement = true;
-    ArraySizes.push_back(llvm::APSInt::get(1));
-  } else {
-    llvm::APSInt ConstantLengthValue;
-    if (!Length->EvaluateAsInt(ConstantLengthValue, Context))
-      return false;
-
-    SingleElement = (ConstantLengthValue.getSExtValue() == 1);
-    ArraySizes.push_back(ConstantLengthValue);
-  }
-
-  // Get the base of this array section and walk up from there.
-  const Expr *Base = OASE->getBase()->IgnoreParenImpCasts();
-
-  // We require length = 1 for all array sections except the right-most to
-  // guarantee that the memory region is contiguous and has no holes in it.
-  while (const auto *TempOASE = dyn_cast<OMPArraySectionExpr>(Base)) {
-    Length = TempOASE->getLength();
-    if (Length == nullptr) {
-      // For array sections of the form [1:] or [:], we would need to analyze
-      // the lower bound...
-      if (OASE->getColonLoc().isValid())
-        return false;
-
-      // This is an array subscript which has implicit length 1!
-      ArraySizes.push_back(llvm::APSInt::get(1));
-    } else {
-      llvm::APSInt ConstantLengthValue;
-      if (!Length->EvaluateAsInt(ConstantLengthValue, Context) ||
-          ConstantLengthValue.getSExtValue() != 1)
-        return false;
-
-      ArraySizes.push_back(ConstantLengthValue);
-    }
-    Base = TempOASE->getBase()->IgnoreParenImpCasts();
-  }
-
-  // If we have a single element, we don't need to add the implicit lengths.
-  if (!SingleElement) {
-    while (const auto *TempASE = dyn_cast<ArraySubscriptExpr>(Base)) {
-      // Has implicit length 1!
-      ArraySizes.push_back(llvm::APSInt::get(1));
-      Base = TempASE->getBase()->IgnoreParenImpCasts();
-    }
-  }
-
-  // This array section can be privatized as a single value or as a constant
-  // sized array.
-  return true;
-}
-
 static bool ActOnOMPReductionKindClause(
     Sema &S, DSAStackTy *Stack, OpenMPClauseKind ClauseKind,
     ArrayRef<Expr *> VarList, SourceLocation StartLoc, SourceLocation LParenLoc,
@@ -9690,26 +9628,7 @@ static bool ActOnOMPReductionKindClause(
     auto *RHSVD = buildVarDecl(S, ELoc, Type, D->getName(),
                                D->hasAttrs() ? &D->getAttrs() : nullptr);
     auto PrivateTy = Type;
-
-    // Try if we can determine constant lengths for all array sections and avoid
-    // the VLA.
-    bool ConstantLengthOASE = false;
-    if (OASE) {
-      bool SingleElement;
-      llvm::SmallVector<llvm::APSInt, 4> ArraySizes;
-      ConstantLengthOASE = CheckOMPArraySectionConstantForReduction(
-          Context, OASE, SingleElement, ArraySizes);
-
-      // If we don't have a single element, we must emit a constant array type.
-      if (ConstantLengthOASE && !SingleElement) {
-        for (auto &Size : ArraySizes) {
-          PrivateTy = Context.getConstantArrayType(
-              PrivateTy, Size, ArrayType::Normal, /*IndexTypeQuals=*/0);
-        }
-      }
-    }
-
-    if ((OASE && !ConstantLengthOASE) ||
+    if (OASE ||
         (!ASE &&
          D->getType().getNonReferenceType()->isVariablyModifiedType())) {
       // For arrays/array sections only: