[OPENMP] Allow to use global variables as lcv in loop-based directives.

For proper codegen we need to capture variable in the OpenMP region. In loop-based directives loop control variables are private by default and they must be captured in this region. There was a problem with capturing of globals, used as lcv, as they was not marked as private by default.
Differential Revision: http://reviews.llvm.org/D9336

llvm-svn: 236201

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -7421,8 +7421,6 @@ def note_omp_implicit_dsa : Note<
   "implicitly determined as %0">;
 def err_omp_loop_var_dsa : Error<
   "loop iteration variable in the associated loop of 'omp %1' directive may not be %0, predetermined as %2">;
-def err_omp_global_loop_var_dsa : Error<
-  "loop iteration variable in the associated loop of 'omp %1' directive may not be a variable with global storage without being explicitly marked as %0">;
 def err_omp_not_for : Error<
   "%select{statement after '#pragma omp %1' must be a for loop|"
   "expected %2 for loops after '#pragma omp %1'%select{|, but found only %4}3}0">;

clang/include/clang/Sema/Sema.h

@@ -7424,6 +7424,12 @@ class Sema {
   /// \brief Called on end of data sharing attribute block.
   void EndOpenMPDSABlock(Stmt *CurDirective);
 
+  /// \brief Check if the current region is an OpenMP loop region and if it is,
+  /// mark loop control variable, used in \p Init for loop initialization, as
+  /// private by default.
+  /// \param Init First part of the for loop.
+  void ActOnOpenMPLoopInitialization(SourceLocation ForLoc, Stmt *Init);
+
   // OpenMP directives and clauses.
   /// \brief Called on correct id-expression from the '#pragma omp
   /// threadprivate'.

clang/lib/Parse/ParseStmt.cpp

@@ -1689,6 +1689,12 @@ StmtResult Parser::ParseForStatement(SourceLocation *TrailingElseLoc) {
                                                      FirstPart.get(),
                                                      Collection.get(),
                                                      T.getCloseLocation());
+  } else {
+    // In OpenMP loop region loop control variable must be captured and be
+    // private. Perform analysis of first part (if any).
+    if (getLangOpts().OpenMP && FirstPart.isUsable()) {
+      Actions.ActOnOpenMPLoopInitialization(ForLoc, FirstPart.get());
+    }
   }
 
   // C99 6.8.5p5 - In C99, the body of the for statement is a scope, even if

clang/lib/Sema/SemaOpenMP.cpp

@@ -82,27 +82,32 @@ class DSAStackTy {
   };
   typedef llvm::SmallDenseMap<VarDecl *, DSAInfo, 64> DeclSAMapTy;
   typedef llvm::SmallDenseMap<VarDecl *, DeclRefExpr *, 64> AlignedMapTy;
+  typedef llvm::DenseSet<VarDecl *> LoopControlVariablesSetTy;
 
   struct SharingMapTy {
     DeclSAMapTy SharingMap;
     AlignedMapTy AlignedMap;
+    LoopControlVariablesSetTy LCVSet;
     DefaultDataSharingAttributes DefaultAttr;
     SourceLocation DefaultAttrLoc;
     OpenMPDirectiveKind Directive;
     DeclarationNameInfo DirectiveName;
     Scope *CurScope;
     SourceLocation ConstructLoc;
     bool OrderedRegion;
+    unsigned CollapseNumber;
     SourceLocation InnerTeamsRegionLoc;
     SharingMapTy(OpenMPDirectiveKind DKind, DeclarationNameInfo Name,
                  Scope *CurScope, SourceLocation Loc)
-        : SharingMap(), AlignedMap(), DefaultAttr(DSA_unspecified),
+        : SharingMap(), AlignedMap(), LCVSet(), DefaultAttr(DSA_unspecified),
           Directive(DKind), DirectiveName(std::move(Name)), CurScope(CurScope),
-          ConstructLoc(Loc), OrderedRegion(false), InnerTeamsRegionLoc() {}
+          ConstructLoc(Loc), OrderedRegion(false), CollapseNumber(1),
+          InnerTeamsRegionLoc() {}
     SharingMapTy()
-        : SharingMap(), AlignedMap(), DefaultAttr(DSA_unspecified),
+        : SharingMap(), AlignedMap(), LCVSet(), DefaultAttr(DSA_unspecified),
           Directive(OMPD_unknown), DirectiveName(), CurScope(nullptr),
-          ConstructLoc(), OrderedRegion(false), InnerTeamsRegionLoc() {}
+          ConstructLoc(), OrderedRegion(false), CollapseNumber(1),
+          InnerTeamsRegionLoc() {}
   };
 
   typedef SmallVector<SharingMapTy, 64> StackTy;
@@ -137,6 +142,12 @@ class DSAStackTy {
   /// for diagnostics.
   DeclRefExpr *addUniqueAligned(VarDecl *D, DeclRefExpr *NewDE);
 
+  /// \brief Register specified variable as loop control variable.
+  void addLoopControlVariable(VarDecl *D);
+  /// \brief Check if the specified variable is a loop control variable for
+  /// current region.
+  bool isLoopControlVariable(VarDecl *D);
+
   /// \brief Adds explicit data sharing attribute to the specified declaration.
   void addDSA(VarDecl *D, DeclRefExpr *E, OpenMPClauseKind A);
 
@@ -209,6 +220,13 @@ class DSAStackTy {
     return false;
   }
 
+  /// \brief Set collapse value for the region.
+  void setCollapseNumber(unsigned Val) { Stack.back().CollapseNumber = Val; }
+  /// \brief Return collapse value for region.
+  unsigned getCollapseNumber() const {
+    return Stack.back().CollapseNumber;
+  }
+
   /// \brief Marks current target region as one with closely nested teams
   /// region.
   void setParentTeamsRegionLoc(SourceLocation TeamsRegionLoc) {
@@ -356,6 +374,18 @@ DeclRefExpr *DSAStackTy::addUniqueAligned(VarDecl *D, DeclRefExpr *NewDE) {
   return nullptr;
 }
 
+void DSAStackTy::addLoopControlVariable(VarDecl *D) {
+  assert(Stack.size() > 1 && "Data-sharing attributes stack is empty");
+  D = D->getCanonicalDecl();
+  Stack.back().LCVSet.insert(D);
+}
+
+bool DSAStackTy::isLoopControlVariable(VarDecl *D) {
+  assert(Stack.size() > 1 && "Data-sharing attributes stack is empty");
+  D = D->getCanonicalDecl();
+  return Stack.back().LCVSet.count(D) > 0;
+}
+
 void DSAStackTy::addDSA(VarDecl *D, DeclRefExpr *E, OpenMPClauseKind A) {
   D = D->getCanonicalDecl();
   if (A == OMPC_threadprivate) {
@@ -556,6 +586,8 @@ bool Sema::IsOpenMPCapturedVar(VarDecl *VD) {
   assert(LangOpts.OpenMP && "OpenMP is not allowed");
   VD = VD->getCanonicalDecl();
   if (DSAStack->getCurrentDirective() != OMPD_unknown) {
+    if (DSAStack->isLoopControlVariable(VD))
+      return true;
     auto DVarPrivate = DSAStack->getTopDSA(VD, /*FromParent=*/false);
     if (DVarPrivate.CKind != OMPC_unknown && isOpenMPPrivate(DVarPrivate.CKind))
       return true;
@@ -1956,7 +1988,7 @@ class OpenMPIterationSpaceChecker {
         TestIsStrictOp(false), SubtractStep(false) {}
   /// \brief Check init-expr for canonical loop form and save loop counter
   /// variable - #Var and its initialization value - #LB.
-  bool CheckInit(Stmt *S);
+  bool CheckInit(Stmt *S, bool EmitDiags = true);
   /// \brief Check test-expr for canonical form, save upper-bound (#UB), flags
   /// for less/greater and for strict/non-strict comparison.
   bool CheckCond(Expr *S);
@@ -2096,7 +2128,7 @@ bool OpenMPIterationSpaceChecker::SetStep(Expr *NewStep, bool Subtract) {
   return false;
 }
 
-bool OpenMPIterationSpaceChecker::CheckInit(Stmt *S) {
+bool OpenMPIterationSpaceChecker::CheckInit(Stmt *S, bool EmitDiags) {
   // Check init-expr for canonical loop form and save loop counter
   // variable - #Var and its initialization value - #LB.
   // OpenMP [2.6] Canonical loop form. init-expr may be one of the following:
@@ -2106,7 +2138,9 @@ bool OpenMPIterationSpaceChecker::CheckInit(Stmt *S) {
   //   pointer-type var = lb
   //
   if (!S) {
-    SemaRef.Diag(DefaultLoc, diag::err_omp_loop_not_canonical_init);
+    if (EmitDiags) {
+      SemaRef.Diag(DefaultLoc, diag::err_omp_loop_not_canonical_init);
+    }
     return true;
   }
   InitSrcRange = S->getSourceRange();
@@ -2122,7 +2156,7 @@ bool OpenMPIterationSpaceChecker::CheckInit(Stmt *S) {
       if (auto Var = dyn_cast_or_null<VarDecl>(DS->getSingleDecl())) {
         if (Var->hasInit()) {
           // Accept non-canonical init form here but emit ext. warning.
-          if (Var->getInitStyle() != VarDecl::CInit)
+          if (Var->getInitStyle() != VarDecl::CInit && EmitDiags)
             SemaRef.Diag(S->getLocStart(),
                          diag::ext_omp_loop_not_canonical_init)
                 << S->getSourceRange();
@@ -2136,8 +2170,10 @@ bool OpenMPIterationSpaceChecker::CheckInit(Stmt *S) {
         return SetVarAndLB(dyn_cast<VarDecl>(DRE->getDecl()), DRE,
                            CE->getArg(1));
 
-  SemaRef.Diag(S->getLocStart(), diag::err_omp_loop_not_canonical_init)
-      << S->getSourceRange();
+  if (EmitDiags) {
+    SemaRef.Diag(S->getLocStart(), diag::err_omp_loop_not_canonical_init)
+        << S->getSourceRange();
+  }
   return true;
 }
 
@@ -2398,7 +2434,8 @@ Expr *OpenMPIterationSpaceChecker::BuildPreCond(Scope *S, Expr *Cond) const {
 /// \brief Build reference expression to the counter be used for codegen.
 Expr *OpenMPIterationSpaceChecker::BuildCounterVar() const {
   return DeclRefExpr::Create(SemaRef.Context, NestedNameSpecifierLoc(),
-                             GetIncrementSrcRange().getBegin(), Var, false,
+                             GetIncrementSrcRange().getBegin(), Var,
+                             /*RefersToEnclosingVariableOrCapture=*/true,
                              DefaultLoc, Var->getType(), VK_LValue);
 }
 
@@ -2434,6 +2471,20 @@ struct LoopIterationSpace {
 
 } // namespace
 
+void Sema::ActOnOpenMPLoopInitialization(SourceLocation ForLoc, Stmt *Init) {
+  assert(getLangOpts().OpenMP && "OpenMP is not active.");
+  assert(Init && "Expected loop in canonical form.");
+  unsigned CollapseIteration = DSAStack->getCollapseNumber();
+  if (CollapseIteration > 0 &&
+      isOpenMPLoopDirective(DSAStack->getCurrentDirective())) {
+    OpenMPIterationSpaceChecker ISC(*this, ForLoc);
+    if (!ISC.CheckInit(Init, /*EmitDiags=*/false)) {
+      DSAStack->addLoopControlVariable(ISC.GetLoopVar());
+    }
+    DSAStack->setCollapseNumber(CollapseIteration - 1);
+  }
+}
+
 /// \brief Called on a for stmt to check and extract its iteration space
 /// for further processing (such as collapsing).
 static bool CheckOpenMPIterationSpace(
@@ -2526,18 +2577,10 @@ static bool CheckOpenMPIterationSpace(
     // Make the loop iteration variable private (for worksharing constructs),
     // linear (for simd directives with the only one associated loop) or
     // lastprivate (for simd directives with several collapsed loops).
-    // FIXME: the next check and error message must be removed once the
-    // capturing of global variables in loops is fixed.
     if (DVar.CKind == OMPC_unknown)
       DVar = DSA.hasDSA(Var, isOpenMPPrivate, MatchesAlways(),
                         /*FromParent=*/false);
-    if (!Var->hasLocalStorage() && DVar.CKind == OMPC_unknown) {
-      SemaRef.Diag(Init->getLocStart(), diag::err_omp_global_loop_var_dsa)
-          << getOpenMPClauseName(PredeterminedCKind)
-          << getOpenMPDirectiveName(DKind);
-      HasErrors = true;
-    } else
-      DSA.addDSA(Var, LoopVarRefExpr, PredeterminedCKind);
+    DSA.addDSA(Var, LoopVarRefExpr, PredeterminedCKind);
   }
 
   assert(isOpenMPLoopDirective(DKind) && "DSA for non-loop vars");
@@ -4210,6 +4253,9 @@ ExprResult Sema::VerifyPositiveIntegerConstantInClause(Expr *E,
         << E->getSourceRange();
     return ExprError();
   }
+  if (CKind == OMPC_collapse) {
+    DSAStack->setCollapseNumber(Result.getExtValue());
+  }
   return ICE;
 }
 

clang/test/OpenMP/for_codegen.cpp

@@ -8,7 +8,11 @@
 #define HEADER
 
 // CHECK: [[IDENT_T_TY:%.+]] = type { i32, i32, i32, i32, i8* }
-// CHECK: [[IMPLICIT_BARRIER_LOC:@.+]] = private unnamed_addr constant %{{.+}} { i32 0, i32 66, i32 0, i32 0, i8*
+// CHECK-DAG: [[IMPLICIT_BARRIER_LOC:@.+]] = private unnamed_addr constant %{{.+}} { i32 0, i32 66, i32 0, i32 0, i8*
+// CHECK-DAG: [[I:@.+]] = global i8 1,
+// CHECK-DAG: [[J:@.+]] = global i8 2,
+// CHECK-DAG: [[K:@.+]] = global i8 3,
+
 // CHECK-LABEL: define {{.*void}} @{{.*}}without_schedule_clause{{.*}}(float* {{.+}}, float* {{.+}}, float* {{.+}}, float* {{.+}})
 void without_schedule_clause(float *a, float *b, float *c, float *d) {
 // CHECK: [[GTID:%.+]] = call i32 @__kmpc_global_thread_num([[IDENT_T_TY]]* [[DEFAULT_LOC:[@%].+]])
@@ -365,5 +369,41 @@ void parallel_for(float *a) {
 // TERM_DEBUG-DAG: [[DBG_LOC_END]] = !DILocation(line: [[@LINE-16]],
 // TERM_DEBUG-DAG: [[DBG_LOC_CANCEL]] = !DILocation(line: [[@LINE-17]],
 
+char i = 1, j = 2, k = 3;
+// CHECK-LABEL: for_with_global_lcv
+void for_with_global_lcv() {
+// CHECK: [[I_ADDR:%.+]] = alloca i8,
+// CHECK: [[J_ADDR:%.+]] = alloca i8,
+
+// CHECK: call void @__kmpc_for_static_init_4(
+// CHECK-NOT: [[I]]
+// CHECK: store i8 %{{.+}}, i8* [[I_ADDR]]
+// CHECK-NOT: [[I]]
+// CHECK: [[I_VAL:%.+]] = load i8, i8* [[I_ADDR]],
+// CHECK-NOT: [[I]]
+// CHECK: store i8 [[I_VAL]], i8* [[K]]
+// CHECK-NOT: [[I]]
+// CHECK: call void @__kmpc_for_static_fini(
+#pragma omp for
+  for (i = 0; i < 2; ++i) {
+    k = i;
+  }
+// CHECK: call void @__kmpc_for_static_init_4(
+// CHECK-NOT: [[J]]
+// CHECK: store i8 %{{.+}}, i8* [[J_ADDR]]
+// CHECK-NOT: [[J]]
+// CHECK: [[J_VAL:%.+]] = load i8, i8* [[J_ADDR]],
+// CHECK-NOT: [[J]]
+// CHECK: store i8 [[J_VAL]], i8* [[K]]
+// CHECK-NOT: [[J]]
+// CHECK: call void @__kmpc_for_static_fini(
+#pragma omp for collapse(2)
+  for (int i = 0; i < 2; ++i)
+  for (j = 0; j < 2; ++j) {
+    k = i;
+    k = j;
+  }
+}
+
 #endif // HEADER
 

clang/test/OpenMP/for_loop_messages.cpp

@@ -313,15 +313,13 @@ int test_iteration_spaces() {
 
 #pragma omp parallel
   {
-// expected-error@+2 {{loop iteration variable in the associated loop of 'omp for' directive may not be a variable with global storage without being explicitly marked as private}}
 #pragma omp for
     for (globalii = 0; globalii < 10; globalii += 1)
       c[globalii] = a[globalii];
   }
 
 #pragma omp parallel
   {
-// expected-error@+3 {{loop iteration variable in the associated loop of 'omp for' directive may not be a variable with global storage without being explicitly marked as private}}
 #pragma omp for collapse(2)
     for (ii = 0; ii < 10; ii += 1)
     for (globalii = 0; globalii < 10; globalii += 1)

clang/test/OpenMP/for_simd_loop_messages.cpp

@@ -314,15 +314,13 @@ int test_iteration_spaces() {
 
 #pragma omp parallel
   {
-// expected-error@+2 {{loop iteration variable in the associated loop of 'omp for simd' directive may not be a variable with global storage without being explicitly marked as linear}}
 #pragma omp for simd
     for (globalii = 0; globalii < 10; globalii += 1)
       c[globalii] = a[globalii];
   }
 
 #pragma omp parallel
   {
-// expected-error@+3 {{loop iteration variable in the associated loop of 'omp for simd' directive may not be a variable with global storage without being explicitly marked as lastprivate}}
 #pragma omp for simd collapse(2)
     for (ii = 0; ii < 10; ii += 1)
     for (globalii = 0; globalii < 10; globalii += 1)

clang/test/OpenMP/parallel_for_loop_messages.cpp

@@ -265,14 +265,12 @@ int test_iteration_spaces() {
   }
 
   {
-// expected-error@+2 {{loop iteration variable in the associated loop of 'omp parallel for' directive may not be a variable with global storage without being explicitly marked as private}}
 #pragma omp parallel for
     for (globalii = 0; globalii < 10; globalii += 1)
       c[globalii] = a[globalii];
   }
 
   {
-// expected-error@+3 {{loop iteration variable in the associated loop of 'omp parallel for' directive may not be a variable with global storage without being explicitly marked as private}}
 #pragma omp parallel for collapse(2)
     for (ii = 0; ii < 10; ii += 1)
     for (globalii = 0; globalii < 10; globalii += 1)

clang/test/OpenMP/parallel_for_simd_loop_messages.cpp

@@ -266,14 +266,12 @@ int test_iteration_spaces() {
   }
 
   {
-// expected-error@+2 {{loop iteration variable in the associated loop of 'omp parallel for simd' directive may not be a variable with global storage without being explicitly marked as linear}}
 #pragma omp parallel for simd
     for (globalii = 0; globalii < 10; globalii += 1)
       c[globalii] = a[globalii];
   }
 
   {
-// expected-error@+3 {{loop iteration variable in the associated loop of 'omp parallel for simd' directive may not be a variable with global storage without being explicitly marked as lastprivate}}
 #pragma omp parallel for simd collapse(2)
     for (ii = 0; ii < 10; ii += 1)
     for (globalii = 0; globalii < 10; globalii += 1)

clang/test/OpenMP/simd_loop_messages.cpp

@@ -260,15 +260,13 @@ int test_iteration_spaces() {
 
   #pragma omp parallel
   {
-    // expected-error@+2 {{loop iteration variable in the associated loop of 'omp simd' directive may not be a variable with global storage without being explicitly marked as linear}}
     #pragma omp simd
     for (globalii = 0; globalii < 10; globalii+=1)
       c[globalii] = a[globalii];
   }
 
   #pragma omp parallel
   {
-// expected-error@+3 {{loop iteration variable in the associated loop of 'omp simd' directive may not be a variable with global storage without being explicitly marked as lastprivate}}
 #pragma omp simd collapse(2)
     for (ii = 0; ii < 10; ii += 1)
     for (globalii = 0; globalii < 10; globalii += 1)