[OPENMP] Loop canonical form analysis (Sema)

[amusman]

Summary

This patch implements semantic analysis to make sure that the loop is in OpenMP canonical form.
This is the form required for 'omp simd', 'omp for' and other loop pragmas.

[rsmith]

lib/Sema/SemaOpenMP.cpp

1284–1343

Wow. I really don't think we should be computing this here. It also seems wrong, since you presumably want to know whether you have contiguously-stored elements, not whether you have random access iterators, right?

1513–1519

Maybe check this when creating the BreakStmt itself? (Clear the BreakScope flag in your OpenMP loop statement's Scope.)

[hfinkel]

lib/Sema/SemaOpenMP.cpp

1284–1343

No, section 2.6 of the OpenMP spec specifically requires a random-access iterator type for the iteration variable; specifically:

var One of the following:

A variable of a signed or unsigned integer type. 
For C++, a variable of a random access iterator type.
For C, a variable of a pointer type.

[ABataev]

Comment at: lib/Sema/SemaOpenMP.cpp:1451-1457
@@ +1450,9 @@
+ // Perform conformance checks of the loop body.
+ ForBreakStmtChecker BreakCheck;
+ if (CurStmt && BreakCheck.Visit(CurStmt)) {
+ for (auto Break : BreakCheck.getBreakStmts())
+ Diag(Break->getLocStart(), diag::err_omp_loop_cannot_break)
+ << getOpenMPDirectiveName(DKind);
+ return true;
+ }

+

Maybe check this when creating the BreakStmt itself? (Clear the BreakScope flag in your OpenMP loop statement's Scope.)

Richard,
But then we will see some bad kind of diagnostic, like "'break'
statement not in loop or switch statement", though actually there is a
loop statement. That's quite confusing.

Best regards,

Alexey Bataev

Software Engineer
Intel Compiler Team
Intel Corp.

23.05.2014 4:32, Richard Smith пишет:

Comment at: lib/Sema/SemaOpenMP.cpp:1222-1281
@@ +1221,62 @@
+
+/ \brief Return true if the given type is pointer or other random access
+/ iterator (currently only std-compatible iterators are allowed here).
+bool Sema::IsRandomAccessIteratorType(QualType Ty, SourceLocation Loc) {
+ if (Ty->isPointerType())
+ return true;
+ if (!getLangOpts().CPlusPlus || !Ty->isOverloadableType())
+ return false;
+ Check that var type is a random access iterator, i.e. we can apply
+ 'std::distance' to the init and test arguments of the for-loop.
+ CXXScopeSpec StdScopeSpec;
+ StdScopeSpec.Extend(Context, getOrCreateStdNamespace(), SourceLocation(),
+ SourceLocation());
+
+ TemplateDecl *TIT = nullptr;
+ {
+ DeclarationNameInfo DNI(&Context.Idents.get("iterator_traits"),
+ SourceLocation());
+ LookupResult LR(*this, DNI, LookupNestedNameSpecifierName);
+ if (!LookupParsedName(LR, DSAStack->getCurScope(), &StdScopeSpec) ||
+ !LR.isSingleResult() || !(TIT = LR.getAsSingle<TemplateDecl>()))
+ return false;
+ }
+
+ CXXRecordDecl *IT = nullptr;
+ {
+ TemplateArgumentListInfo Args;
+ TemplateArgument Arg(Ty);
+ TemplateArgumentLoc ArgLoc(Arg, Context.CreateTypeSourceInfo(Ty));
+ Args.addArgument(ArgLoc);
+ QualType T = CheckTemplateIdType(TemplateName(TIT), SourceLocation(), Args);
+ if (T.isNull() || RequireCompleteType(Loc, T, 0) ||
+ !(IT = T->getAsCXXRecordDecl()))
+ return false;
+ }
+
+ TypeDecl *RAI = nullptr;
+ {
+ DeclarationNameInfo DNI(&Context.Idents.get("random_access_iterator_tag"),
+ SourceLocation());
+ LookupResult LR(*this, DNI, LookupOrdinaryName);
+ CXXRecordDecl *RDType = Ty->getAsCXXRecordDecl();
+ if (!LookupParsedName(LR, DSAStack->getCurScope(), &StdScopeSpec) ||
+ !LR.isSingleResult() || !(RAI = LR.getAsSingle<TypeDecl>()) || !RDType)
+ return false;
+ }
+
+ TypeDecl *IC = nullptr;
+ {
+ DeclarationNameInfo DNI(&Context.Idents.get("iterator_category"),
+ SourceLocation());
+ LookupResult LR(*this, DNI, LookupOrdinaryName);
+ if (!LookupQualifiedName(LR, IT) || !LR.isSingleResult() ||
+ !(IC = LR.getAsSingle<TypeDecl>()) ||
+ !Context.hasSameType(Context.getTypeDeclType(RAI),
+ Context.getTypeDeclType(IC)))
+ return false;
+ }
+
+ return true;
+}

+

Wow. I really don't think we should be computing this here. It also seems wrong, since you presumably want to know whether you have contiguously-stored elements, not whether you have random access iterators, right?

Comment at: lib/Sema/SemaOpenMP.cpp:1451-1457
@@ +1450,9 @@
+ // Perform conformance checks of the loop body.
+ ForBreakStmtChecker BreakCheck;
+ if (CurStmt && BreakCheck.Visit(CurStmt)) {
+ for (auto Break : BreakCheck.getBreakStmts())
+ Diag(Break->getLocStart(), diag::err_omp_loop_cannot_break)
+ << getOpenMPDirectiveName(DKind);
+ return true;
+ }

+

Maybe check this when creating the BreakStmt itself? (Clear the BreakScope flag in your OpenMP loop statement's Scope.)

http://reviews.llvm.org/D3778

[amusman]

Richard,

Thank you for review.

lib/Sema/SemaOpenMP.cpp

1284–1343

Basically it would be OK to have as a loop counter any type, which value at any iteration can be calculated in constant time using "begin" and the current iteration's number (of some integer type), if we knew how to calculate it. As noted by Hal, it is explicitly allowed by OpenMP 4 for random access iterators - for example, it specifies that the type in which the loop count is: "For C++, if var is of a random access iterator type, then the type is the type that would be used by std::distance applied to variables of the type of var.". This is why we need a check that there is std::distance.

1513–1519

How do you think, it is worth adding a bit in Scope, to modify error message (this seems to me a rare enough case)?
There is already an "OpenMPDirectiveScope" bit, but not all openmp directives prohibit break stmts.

[rsmith]

lib/Sema/SemaOpenMP.cpp

1284–1343

OK. This still seems strange to me, but I agree that the OpenMP spec appears to want this.

The next question is, what does it mean by "a random access iterator type"? In the C++ standard, that does not mean "std::iterator_traits<T>::iterator_category is derived from std::random_access_iterator_tag". It means that the type conforms to the requirements of a random access iterator (see 24.2.7 [random.access.iterators] p1). And that's not actually a computable property.

Is a diagnostic really required here, or should we just *assume* that the iteration variable is a random access iterator, use the operations which the random access iterator requirements require to exist, and produce the relevant diagnostics if they didn't work? (That's how range-based for loops work, for instance.)

1513–1519

Adding a bit to Scope to indicate that it is an OpenMP scope that prohibits break statements seems fine to me. (Be careful to bump Flags from unsigned short to unsigned int at the same time, and reorder it before Depth to avoid unnecessary padding.)

[amusman]

Richard,

Yes, I think that assuming that the variable is random access iterator would work. It will still need to generate std::difference on them, but we can check that later, during building expressions for iteration space (that will be used for CodeGen). This also has an advantage that user may use his iterators without deriving from std classes.
I've removed corresponding checks and fixed processing break statements.

Thanks,
Alexander

[rsmith]

include/clang/Basic/DiagnosticSemaKinds.td

6978

What does "dsa" stand for?

6980–6992

This seems like too many different ways of saying the same thing to me. How about something like:

initialization clause of OpenMP for loop must be of the form 'var = init' or 'T var = init'

6981

Please write this as OpenMP, not as openmp.
Use 'must', not 'should'; this is a hard requirement.

6993–6996

How about replacing both of these with:

condition of OpenMP for loop must be a relational comparison ('<', '<=', '>', or '>=') of loop variable %0

6997–7002

How about:

increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable %0

7005–7006

Maybe

increment step of OpenMP for loop is of non-integer type %0

7008–7009

Please mention in the diagnostic that the reason for this rule is that this is an OpenMP for loop.

7012–7015

Perhaps replace both of these with

%q0 statement cannot be used in OpenMP for loop

include/clang/Sema/Sema.h

7306–7308

It looks like neither of these needs to be a member of Sema: make them static functions inside SemaOpenMP instead?

lib/Sema/SemaOpenMP.cpp

841

Please call this SemaRef or Owner or some other common name. The Parser calls Sema Actions for reasons that aren't relevant in this case.

864

This comment is strangely-worded.

874

Please capitalize these references to other members properly, and refer to them as #Var and #LB (that's what makes Doxygen happy, apparently).

888

"Check the right-hand side of an assignment in the increment expression."

904–908

This is all redundant. Just use Var->getType()->isDependentType().

910–913

This is also redundant. Just LB && (LB->isValueDependent() || LB->isInstantiationDependent()) would do. (Type-dependence implies value-dependence and instantiation-dependence, and an unexpanded pack implies instantiation-dependence.)

That said, I think all you actually care about here is value-dependence (that is, whether we're able to constant-evaluate the bound).

Likewise for the following two checks.

914–921

Copy-paste error here. I assume you intended to check Step?

957–959

I think you only care about whether NewStep is value-dependent here.

967

You've already issued a diagnostic for this case inside PerformImplicitIntegerConversion.

983–998

Hmm, you give an error if the increment is a constant and allow it if it's not. I suppose that makes some sense, but it seems really weird. The rule from the OpenMP spec is extremely vague about this...

1011–1013

Is this really supposed to be a syntactic check? It bans reasonable things like:

#pragma omp simd(...)
for (int (*p)[4] = lb; p != lb + 8; ++p)

1049–1050

This isn't the right check: you should look at Var->getInitStyle() to check that the declaration was of a form involving an = (but that seems like a bizarre and unnecessary rule, so maybe this should be an ExtWarn). As this stands, you'll accept braced and parenthesized initialization, and do the wrong thing in the presence of default constructors with default arguments.

1056

This seems strange, and possibly incorrect. The argument might be of a type entirely unrelated to the iterator type, and may not provide the lower bound for the iteration. Why are you pulling out the first argument here?

1076

"may be the loop variable"

1173

IsAdd would make more sense; we generally use "increment" to mean only ++.

1179

Likewise.

1185

This looks wrong: both + and - can be overloaded as unary operators.

1313–1316

Don't canonicalize the type here. Also, why are you stripping off references? The spec doesn't imply that you should do that as far as I can see.

1364

Do you have some reference to the OpenMP spec to justify this?

1382–1411

Please check this when building these statements, as you do for break, rather than performing an additional visit of them after the fact.

[amusman]

include/clang/Basic/DiagnosticSemaKinds.td

6978

Data-sharing Attributes (term from OpenMP, section 2.14.1). I moved this to be near other _dsa error diagnostic messages.

6980–6992

OK

6993–6996

OK

6997–7002

OK

7005–7006

I removed this message - it turns out, this is already checked by PerformImplicitIntegerConversion.

7008–7009

OK

7012–7015

I suggest to change the second message to refer to "OpenMP simd region" - the first one is related to ('break' stmts in) the loop and the second - to the loop and all nested loops/other statements.

include/clang/Sema/Sema.h

7306–7308

Fixed.

lib/Sema/SemaOpenMP.cpp

841

Fixed. There are actually several other 'Actions' in SemaOpenMP.cpp unrelated to my change, I plan to fix them in separate commit.

864

Changed to "This flag is true when step is subtracted on each iteration."

874

OK

888

OK

904–908

OK

910–913

OK

914–921

Yes, this was a bug.

957–959

Yes, fixed.

967

OK

983–998

Yes, if the increment is not constant, we have to assume that it is loop-invariant and that it is compatible with loop condition, we'll need to calculate it once before the loop.

1011–1013

Well, in this case init is accepted.
In some cases it would be also possible to allow '!=' in condition ( e.g., as operation here is '++', we would expect '<' instead of '!=' ), under some ext-warning. Though, I would prefer to not allow it for now.

1049–1050

OK, changed it to ext-warning.

1056

Fixed.

1076

Fixed.

1173

OK

1179

OK

1185

Fixed.

1313–1316

OK

1364

I've added a comment.
It's a helper routine to skip braces around for stmt, to get a nested for stmt, for example in the following case:

#pragma omp simd collapse(2)
for (int i = 0; i < n; ++i) {
  for (int j = 0; j < n; ++j)
    foo();
}

1382–1411

OK

[amusman]

Hi Richard,

Thank you for review. I believe I've fixed all your comments.

Best regards,
Alexander

[rsmith]

include/clang/Sema/Scope.h

399–406

Please either handle this by copying the OpenMPSimdDirectiveScope to relevant child scopes in Scope::Init or by adding an OpenMPSimdDirectiveParent (if you actually need to know which parent scope had the directive).

Also, this loop doesn't look entirely correct: I would expect that simd-ness shouldn't propagate into (say) local classes declared within an OpenMP simd directive:

void f() {
  #pragma omp simd ...
  for (...) {
    struct S {
      void g() { throw 0; }
    };
  }
}

... but I'm not sure what the OpenMP spec says about this case.

include/clang/Sema/Sema.h

7264

Should this have a name involving OpenMP? It's not obvious from the declaration that this isn't a general-purpose utility.

lib/Sema/SemaOpenMP.cpp

1018–1020

No braces around a single-line if body.

1270–1271

What's this for? If HasErrors is true here, then we've found and diagnosed a problem despite some part of the loop being dependent, and we should return true.

[amusman]

include/clang/Sema/Scope.h

399–406

The OpenMP spec does not cover such cases, but yes, it seems reasonable to allow EH here.

include/clang/Sema/Sema.h

7264

OK, I've renamed it to PerformOpenMPImplicitIntegerConversion

lib/Sema/SemaOpenMP.cpp

1018–1020

Fixed

1270–1271

I agree, fixed.

[amusman]

Here is updated patch.

Thanks,
Alexander

[rsmith]

LGTM

lib/Sema/SemaOpenMP.cpp

1269–1270

You could remove this, and the function Dependent itself. I guess maybe you're keeping it because you'll want this check once you implement the FIXME below? If so, this is fine to leave here.

test/OpenMP/simd_loop_messages.cpp

475–476

You can drop the 1s here.

[amusman]

Closed by commit rL210095 (authored by @amusman).

[kkwli0]

I reviewed the change. I have no comment.

include/clang/Basic/DiagnosticGroups.td

 def ASMOperandWidths : DiagGroup<"asm-operand-widths">;
 def ASM : DiagGroup<"asm", [
     ASMOperandWidths
   ]>;
 
 // OpenMP warnings.
 def SourceUsesOpenMP : DiagGroup<"source-uses-openmp">;
 def OpenMPClauses : DiagGroup<"openmp-clauses">;
+def OpenMPLoopForm : DiagGroup<"openmp-loop-form">;
 
 // Backend warnings.
 def BackendInlineAsm : DiagGroup<"inline-asm">;
 def BackendFrameLargerThan : DiagGroup<"frame-larger-than">;
 def BackendPlugin : DiagGroup<"backend-plugin">;
 def RemarkBackendPlugin : DiagGroup<"remark-backend-plugin">;
 def BackendOptimizationRemark : DiagGroup<"pass">;
 def BackendOptimizationRemarkMissed : DiagGroup<"pass-missed">;
 def BackendOptimizationRemarkAnalysis : DiagGroup<"pass-analysis">;
 
 // Instrumentation based profiling warnings.
 def ProfileInstrOutOfDate : DiagGroup<"profile-instr-out-of-date">;

include/clang/Basic/DiagnosticSemaKinds.td

 def err_omp_no_dsa_for_variable : Error<
   "variable %0 must have explicitly specified data sharing attributes">;
 def err_omp_wrong_dsa : Error<
   "%0 variable cannot be %1">;
 def note_omp_explicit_dsa : Note<
   "defined as %0">;
 def note_omp_predetermined_dsa : Note<
   "predetermined as %0">;
+def err_omp_loop_var_dsa : Error<
+  "loop iteration variable may not be %0">;
 def err_omp_not_for : Error<
   "statement after '#pragma omp %0' must be a for loop">;
 def err_omp_negative_expression_in_clause : Error<
   "argument to '%0' clause must be a positive integer value">;
 def err_omp_not_integral : Error<
   "expression must have integral or unscoped enumeration "
   "type, not %0">;
 def err_omp_incomplete_type : Error<

 def err_omp_aligned_expected_array_or_ptr : Error<
   "argument of aligned clause should be array"
   "%select{ or pointer|, pointer, reference to array or reference to pointer}1"
   ", not %0">;
 def err_omp_aligned_twice : Error<
   "a variable cannot appear in more than one aligned clause">;
 def err_omp_local_var_in_threadprivate_init : Error<
   "variable with local storage in initial value of threadprivate variable">;
+def err_omp_loop_not_canonical_init : Error<
+  "initialization clause of OpenMP for loop must be of the form "
+  "'var = init' or 'T var = init'">;
+def ext_omp_loop_not_canonical_init : ExtWarn<
+  "initialization clause of OpenMP for loop is not in canonical form "
+  "('var = init' or 'T var = init')">, InGroup<OpenMPLoopForm>;
+def err_omp_loop_not_canonical_cond : Error<
+  "condition of OpenMP for loop must be a relational comparison "
+  "('<', '<=', '>', or '>=') of loop variable %0">;
+def err_omp_loop_not_canonical_incr : Error<
+  "increment clause of OpenMP for loop must perform simple addition "
+  "or subtraction on loop variable %0">;
+def err_omp_loop_variable_type : Error<
+  "variable must be of integer or %select{pointer|random access iterator}0 type">;
+def err_omp_loop_incr_not_compatible : Error<
+  "increment expression must cause %0 to %select{decrease|increase}1 "
+  "on each iteration of OpenMP for loop">;
+def note_omp_loop_cond_requres_compatible_incr : Note<
+  "loop step is expected to be %select{negative|positive}0 due to this condition">;
+def err_omp_loop_cannot_use_stmt : Error<
+  "'%0' statement cannot be used in OpenMP for loop">;
+def err_omp_simd_region_cannot_use_stmt : Error<
+  "'%0' statement cannot be used in OpenMP simd region">;
 } // end of OpenMP category
 
 let CategoryName = "Related Result Type Issue" in {
 // Objective-C related result type compatibility
 def warn_related_result_type_compatibility_class : Warning<
   "method is expected to return an instance of its class type "
   "%diff{$, but is declared to return $|"
   ", but is declared to return different type}0,1">;
 def warn_related_result_type_compatibility_protocol : Warning<
   "protocol method is expected to return an instance of the implementing "
   "class, but is declared to return %0">;
 def note_related_result_type_family : Note<
   "%select{overridden|current}0 method is part of the '%select{|alloc|copy|init|"
   "mutableCopy|new|autorelease|dealloc|finalize|release|retain|retainCount|"
   "self}1' method family%select{| and is expected to return an instance of its "
   "class type}0">;
 def note_related_result_type_overridden : Note<
   "overridden method returns an instance of its class type">;
 def note_related_result_type_inferred : Note<
   "%select{class|instance}0 method %1 is assumed to return an instance of "
   "its receiver type (%2)">;
 def note_related_result_type_explicit : Note<
   "%select{overridden|current}0 method is explicitly declared 'instancetype'"

include/clang/Sema/Scope.h

enum ScopeFlags {
     SwitchScope = 0x1000,
 
     /// \brief This is the scope of a C++ try statement.
     TryScope = 0x2000,
 
     /// \brief This is the scope for a function-level C++ try or catch scope.
     FnTryCatchScope = 0x4000,
 
-    /// \brief This is the scope of OpenMP executable directive
-    OpenMPDirectiveScope = 0x8000
+    /// \brief This is the scope of OpenMP executable directive.
+    OpenMPDirectiveScope = 0x8000,
+
+    /// \brief This is the scope of some OpenMP loop directive.
+    OpenMPLoopDirectiveScope = 0x10000,
+
+    /// \brief This is the scope of some OpenMP simd directive.
+    /// For example, it is used for 'omp simd', 'omp for simd'.
+    OpenMPSimdDirectiveScope = 0x20000
   };
 private:
   /// The parent scope for this scope.  This is null for the translation-unit
   /// scope.
   Scope *AnyParent;
 
+  /// Flags - This contains a set of ScopeFlags, which indicates how the scope
+  /// interrelates with other control flow statements.
+  unsigned Flags;
+
   /// Depth - This is the depth of this scope.  The translation-unit scope has
   /// depth 0.
   unsigned short Depth;
 
-  /// Flags - This contains a set of ScopeFlags, which indicates how the scope
-  /// interrelates with other control flow statements.
-  unsigned short Flags;
-
   /// \brief Declarations with static linkage are mangled with the number of
   /// scopes seen as a component.
   unsigned short MSLocalManglingNumber;
 
   /// PrototypeDepth - This is the number of function prototype scopes
   /// enclosing this scope, including this scope.
   unsigned short PrototypeDepth;
 
bool isSwitchScope() const {
     return false;
   }
 
   /// \brief Determines whether this scope is the OpenMP directive scope
   bool isOpenMPDirectiveScope() const {
     return (getFlags() & Scope::OpenMPDirectiveScope);
   }
 
+  /// \brief Determine whether this scope is some OpenMP loop directive scope
+  /// (for example, 'omp for', 'omp simd').
+  bool isOpenMPLoopDirectiveScope() const {
+    if (getFlags() & Scope::OpenMPLoopDirectiveScope) {
+      assert(isOpenMPDirectiveScope() &&
+             "OpenMP loop directive scope is not a directive scope");
+      return true;
+    }
+    return false;
+  }
+
+  /// \brief Determine whether this scope is some OpenMP loop simd directive
+  /// scope (for example, 'omp simd', 'omp for simd').
+  bool isOpenMPSimdDirectiveScope() const {
+    if (getFlags() & Scope::OpenMPSimdDirectiveScope) {
+      assert(isOpenMPLoopDirectiveScope() &&
+             "OpenMP simd directive scope is not a loop directive scope");
+      return true;
+    }
+    return false;
+  }
+
+  /// \brief Determine whether this scope is a loop having OpenMP loop
+  /// directive attached.
+  bool isOpenMPLoopScope() const {
+    const Scope *P = getParent();
+    return P && P->isOpenMPLoopDirectiveScope();
+  }
+
+  /// \brief Determine whether this scope is nested into some OpenMP simd
+  /// directive scope.
+  bool isOpenMPSimdNestedScope() const {
+    for (const Scope *S = getParent(); S; S = S->getParent())
+      if (S->isOpenMPSimdDirectiveScope())
+        return true;
+    return false;
+  }
+
   /// \brief Determine whether this scope is a C++ 'try' block.
   bool isTryScope() const { return getFlags() & Scope::TryScope; }
 
   /// containedInPrototypeScope - Return true if this or a parent scope
   /// is a FunctionPrototypeScope.
   bool containedInPrototypeScope() const;
 
   void PushUsingDirective(UsingDirectiveDecl *UDir) {

include/clang/Sema/Sema.h

void AddAlignedAttr(SourceRange AttrRange, Decl *D, TypeSourceInfo *T,
                       unsigned SpellingListIndex, bool IsPackExpansion);
 
   // OpenMP directives and clauses.
 private:
   void *VarDataSharingAttributesStack;
   /// \brief Initialization of data-sharing attributes stack.
   void InitDataSharingAttributesStack();
   void DestroyDataSharingAttributesStack();
-  ExprResult PerformImplicitIntegerConversion(SourceLocation OpLoc, Expr *Op);
   ExprResult VerifyPositiveIntegerConstantInClause(Expr *Op,
                                                    OpenMPClauseKind CKind);
 public:
+  ExprResult PerformImplicitIntegerConversion(SourceLocation OpLoc, Expr *Op);
   /// \brief Called on start of new data sharing attribute block.
   void StartOpenMPDSABlock(OpenMPDirectiveKind K,
                            const DeclarationNameInfo &DirName,
                            Scope *CurScope);
   /// \brief Called on end of data sharing attribute block.
   void EndOpenMPDSABlock(Stmt *CurDirective);
 
   // OpenMP directives and clauses.
StmtResult ActOnOpenMPParallelDirective(ArrayRef<OMPClause *> Clauses,
                                           Stmt *AStmt,
                                           SourceLocation StartLoc,
                                           SourceLocation EndLoc);
   /// \brief Called on well-formed '\#pragma omp simd' after parsing
   /// of the associated statement.
   StmtResult ActOnOpenMPSimdDirective(ArrayRef<OMPClause *> Clauses,
                                       Stmt *AStmt,
                                       SourceLocation StartLoc,
                                       SourceLocation EndLoc);
 
   OMPClause *ActOnOpenMPSingleExprClause(OpenMPClauseKind Kind,
                                          Expr *Expr,
                                          SourceLocation StartLoc,
                                          SourceLocation LParenLoc,
                                          SourceLocation EndLoc);
   /// \brief Called on well-formed 'if' clause.
   OMPClause *ActOnOpenMPIfClause(Expr *Condition, SourceLocation StartLoc,
                                  SourceLocation LParenLoc,
                                  SourceLocation EndLoc);

lib/Parse/ParseOpenMP.cpp

 ///
 StmtResult Parser::ParseOpenMPDeclarativeOrExecutableDirective() {
   assert(Tok.is(tok::annot_pragma_openmp) && "Not an OpenMP directive!");
   ParenBraceBracketBalancer BalancerRAIIObj(*this);
   SmallVector<Expr *, 5> Identifiers;
   SmallVector<OMPClause *, 5> Clauses;
   SmallVector<llvm::PointerIntPair<OMPClause *, 1, bool>, OMPC_unknown + 1>
   FirstClauses(OMPC_unknown + 1);
-  const unsigned ScopeFlags =
+  unsigned ScopeFlags =
       Scope::FnScope | Scope::DeclScope | Scope::OpenMPDirectiveScope;
   SourceLocation Loc = ConsumeToken(), EndLoc;
   OpenMPDirectiveKind DKind = Tok.isAnnotation()
                                   ? OMPD_unknown
                                   : getOpenMPDirectiveKind(PP.getSpelling(Tok));
   // Name of critical directive.
   DeclarationNameInfo DirName;
   StmtResult Directive = StmtError();
case OMPD_simd: {
     }
     // End location of the directive.
     EndLoc = Tok.getLocation();
     // Consume final annot_pragma_openmp_end.
     ConsumeToken();
 
     StmtResult AssociatedStmt;
     bool CreateDirective = true;
+    if (DKind == OMPD_simd)
+      ScopeFlags |=
+          Scope::OpenMPLoopDirectiveScope | Scope::OpenMPSimdDirectiveScope;
     ParseScope OMPDirectiveScope(this, ScopeFlags);
     {
       // The body is a block scope like in Lambdas and Blocks.
       Sema::CompoundScopeRAII CompoundScope(Actions);
       Actions.ActOnOpenMPRegionStart(DKind, Loc, getCurScope());
       Actions.ActOnStartOfCompoundStmt();
       // Parse statement
       AssociatedStmt = ParseStatement();

lib/Sema/Scope.cpp

if (Flags & FnScope) {
       OS << "TryScope";
       Flags &= ~TryScope;
     } else if (Flags & FnTryCatchScope) {
       OS << "FnTryCatchScope";
       Flags &= ~FnTryCatchScope;
     } else if (Flags & OpenMPDirectiveScope) {
       OS << "OpenMPDirectiveScope";
       Flags &= ~OpenMPDirectiveScope;
+    } else if (Flags & OpenMPLoopDirectiveScope) {
+      OS << "OpenMPLoopDirectiveScope";
+      Flags &= ~OpenMPLoopDirectiveScope;
+    } else if (Flags & OpenMPSimdDirectiveScope) {
+      OS << "OpenMPSimdDirectiveScope";
+      Flags &= ~OpenMPSimdDirectiveScope;
     }
 
     if (Flags)
       OS << " | ";
   }
   if (HasFlags)
     OS << '\n';
 

lib/Sema/SemaExprCXX.cpp

 }
 
 ExprResult Sema::BuildCXXThrow(SourceLocation OpLoc, Expr *Ex, 
                                bool IsThrownVarInScope) {
   // Don't report an error if 'throw' is used in system headers.
   if (!getLangOpts().CXXExceptions &&
       !getSourceManager().isInSystemHeader(OpLoc))
     Diag(OpLoc, diag::err_exceptions_disabled) << "throw";
-  
+  if (getCurScope() && getCurScope()->isOpenMPSimdNestedScope())
+    Diag(OpLoc, diag::err_omp_simd_region_cannot_use_stmt) << "throw";
+
   if (Ex && !Ex->isTypeDependent()) {
     ExprResult ExRes = CheckCXXThrowOperand(OpLoc, Ex, IsThrownVarInScope);
     if (ExRes.isInvalid())
       return ExprError();
     Ex = ExRes.get();
   }
   
   return new (Context)

lib/Sema/SemaOpenMP.cpp

StmtResult Sema::ActOnOpenMPParallelDirective(ArrayRef<OMPClause *> Clauses,
   CS->getCapturedDecl()->setNothrow();
 
   getCurFunction()->setHasBranchProtectedScope();
 
   return OMPParallelDirective::Create(Context, StartLoc, EndLoc, Clauses,
                                       AStmt);
 }
 
+namespace {
+/// \brief Helper class for checking canonical form of the OpenMP loops and
+/// extracting iteration space of each loop in the loop nest, that will be used
+/// for IR generation.
+class OpenMPIterationSpaceChecker {
+  /// \brief Reference to Sema.
+  Sema &SemaRef;
+  /// \brief A location for diagnostics (when there is no some better location).
+  SourceLocation DefaultLoc;
+  /// \brief A location for diagnostics (when increment is not compatible).
+  SourceLocation ConditionLoc;
+  /// \brief A source location for referring to condition later.
+  SourceRange ConditionSrcRange;
+  /// \brief Loop variable.
+  VarDecl *Var;
+  /// \brief Lower bound (initializer for the var).
+  Expr *LB;
+  /// \brief Upper bound.
+  Expr *UB;
+  /// \brief Loop step (increment).
+  Expr *Step;
+  /// \brief This flag is true when condition is one of:
+  ///   Var <  UB
+  ///   Var <= UB
+  ///   UB  >  Var
+  ///   UB  >= Var
+  bool TestIsLessOp;
+  /// \brief This flag is true when condition is strict ( < or > ).
+  bool TestIsStrictOp;
+  /// \brief This flag is true when step is subtracted on each iteration.
+  bool SubtractStep;
+
+public:
+  OpenMPIterationSpaceChecker(Sema &SemaRef, SourceLocation DefaultLoc)
+      : SemaRef(SemaRef), DefaultLoc(DefaultLoc), ConditionLoc(DefaultLoc),
+        ConditionSrcRange(SourceRange()), Var(nullptr), LB(nullptr),
+        UB(nullptr), Step(nullptr), TestIsLessOp(false), 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);
+  /// \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);
+  /// \brief Check incr-expr for canonical loop form and return true if it
+  /// does not conform, otherwise save loop step (#Step).
+  bool CheckInc(Expr *S);
+  /// \brief Return the loop counter variable.
+  VarDecl *GetLoopVar() const { return Var; }
+  /// \brief Return true if any expression is dependent.
+  bool Dependent() const;
+
+private:
+  /// \brief Check the right-hand side of an assignment in the increment
+  /// expression.
+  bool CheckIncRHS(Expr *RHS);
+  /// \brief Helper to set loop counter variable and its initializer.
+  bool SetVarAndLB(VarDecl *NewVar, Expr *NewLB);
+  /// \brief Helper to set upper bound.
+  bool SetUB(Expr *NewUB, bool LessOp, bool StrictOp, const SourceRange &SR,
+             const SourceLocation &SL);
+  /// \brief Helper to set loop increment.
+  bool SetStep(Expr *NewStep, bool Subtract);
+};
+
+bool OpenMPIterationSpaceChecker::Dependent() const {
+  if (!Var) {
+    assert(!LB && !UB && !Step);
+    return false;
+  }
+  return Var->getType()->isDependentType() || (LB && LB->isValueDependent()) ||
+         (UB && UB->isValueDependent()) || (Step && Step->isValueDependent());
+}
+
+bool OpenMPIterationSpaceChecker::SetVarAndLB(VarDecl *NewVar, Expr *NewLB) {
+  // State consistency checking to ensure correct usage.
+  assert(Var == nullptr && LB == nullptr && UB == nullptr && Step == nullptr &&
+         !TestIsLessOp && !TestIsStrictOp);
+  if (!NewVar || !NewLB)
+    return true;
+  Var = NewVar;
+  LB = NewLB;
+  return false;
+}
+
+bool OpenMPIterationSpaceChecker::SetUB(Expr *NewUB, bool LessOp, bool StrictOp,
+                                        const SourceRange &SR,
+                                        const SourceLocation &SL) {
+  // State consistency checking to ensure correct usage.
+  assert(Var != nullptr && LB != nullptr && UB == nullptr && Step == nullptr &&
+         !TestIsLessOp && !TestIsStrictOp);
+  if (!NewUB)
+    return true;
+  UB = NewUB;
+  TestIsLessOp = LessOp;
+  TestIsStrictOp = StrictOp;
+  ConditionSrcRange = SR;
+  ConditionLoc = SL;
+  return false;
+}
+
+bool OpenMPIterationSpaceChecker::SetStep(Expr *NewStep, bool Subtract) {
+  // State consistency checking to ensure correct usage.
+  assert(Var != nullptr && LB != nullptr && Step == nullptr);
+  if (!NewStep)
+    return true;
+  if (!NewStep->isValueDependent()) {
+    // Check that the step is integer expression.
+    SourceLocation StepLoc = NewStep->getLocStart();
+    ExprResult Val = SemaRef.PerformImplicitIntegerConversion(StepLoc, NewStep);
+    if (Val.isInvalid())
+      return true;
+    NewStep = Val.get();
+
+    // OpenMP [2.6, Canonical Loop Form, Restrictions]
+    //  If test-expr is of form var relational-op b and relational-op is < or
+    //  <= then incr-expr must cause var to increase on each iteration of the
+    //  loop. If test-expr is of form var relational-op b and relational-op is
+    //  > or >= then incr-expr must cause var to decrease on each iteration of
+    //  the loop.
+    //  If test-expr is of form b relational-op var and relational-op is < or
+    //  <= then incr-expr must cause var to decrease on each iteration of the
+    //  loop. If test-expr is of form b relational-op var and relational-op is
+    //  > or >= then incr-expr must cause var to increase on each iteration of
+    //  the loop.
+    llvm::APSInt Result;
+    bool IsConstant = NewStep->isIntegerConstantExpr(Result, SemaRef.Context);
+    bool IsUnsigned = !NewStep->getType()->hasSignedIntegerRepresentation();
+    bool IsConstNeg =
+        IsConstant && Result.isSigned() && (Subtract != Result.isNegative());
+    bool IsConstZero = IsConstant && !Result.getBoolValue();
+    if (UB && (IsConstZero ||
+               (TestIsLessOp ? (IsConstNeg || (IsUnsigned && Subtract))
+                             : (!IsConstNeg || (IsUnsigned && !Subtract))))) {
+      SemaRef.Diag(NewStep->getExprLoc(),
+                   diag::err_omp_loop_incr_not_compatible)
+          << Var << TestIsLessOp << NewStep->getSourceRange();
+      SemaRef.Diag(ConditionLoc,
+                   diag::note_omp_loop_cond_requres_compatible_incr)
+          << TestIsLessOp << ConditionSrcRange;
+      return true;
+    }
+  }
+
+  Step = NewStep;
+  SubtractStep = Subtract;
+  return false;
+}
+
+bool OpenMPIterationSpaceChecker::CheckInit(Stmt *S) {
+  // 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:
+  //   var = lb
+  //   integer-type var = lb
+  //   random-access-iterator-type var = lb
+  //   pointer-type var = lb
+  //
+  if (!S) {
+    SemaRef.Diag(DefaultLoc, diag::err_omp_loop_not_canonical_init);
+    return true;
+  }
+  if (Expr *E = dyn_cast<Expr>(S))
+    S = E->IgnoreParens();
+  if (auto BO = dyn_cast<BinaryOperator>(S)) {
+    if (BO->getOpcode() == BO_Assign)
+      if (auto DRE = dyn_cast<DeclRefExpr>(BO->getLHS()->IgnoreParens()))
+        return SetVarAndLB(dyn_cast<VarDecl>(DRE->getDecl()), BO->getLHS());
+  } else if (auto DS = dyn_cast<DeclStmt>(S)) {
+    if (DS->isSingleDecl()) {
+      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)
+            SemaRef.Diag(S->getLocStart(),
+                         diag::ext_omp_loop_not_canonical_init)
+                << S->getSourceRange();
+          return SetVarAndLB(Var, Var->getInit());
+        }
+      }
+    }
+  } else if (auto CE = dyn_cast<CXXOperatorCallExpr>(S)) {
+    if (CE->getOperator() == OO_Equal) {
+      if (auto DRE = dyn_cast<DeclRefExpr>(CE->getArg(0))) {
+        return SetVarAndLB(dyn_cast<VarDecl>(DRE->getDecl()), CE->getArg(1));
+      }
+    }
+  }
+  SemaRef.Diag(S->getLocStart(), diag::err_omp_loop_not_canonical_init)
+      << S->getSourceRange();
+  return true;
+}
+
+/// \brief Ignore parenthesises, implicit casts, copy constructor and return the
+/// variable (which may be the loop variable) if possible.
+static const VarDecl *GetInitVarDecl(const Expr *E) {
+  if (!E)
+    return 0;
+  E = E->IgnoreParenImpCasts();
+  if (auto *CE = dyn_cast_or_null<CXXConstructExpr>(E))
+    if (const CXXConstructorDecl *Ctor = CE->getConstructor())
+      if (Ctor->isCopyConstructor() && CE->getNumArgs() == 1 &&
+          CE->getArg(0) != nullptr)
+        E = CE->getArg(0)->IgnoreParenImpCasts();
+  auto DRE = dyn_cast_or_null<DeclRefExpr>(E);
+  if (!DRE)
+    return nullptr;
+  return dyn_cast<VarDecl>(DRE->getDecl());
+}
+
+bool OpenMPIterationSpaceChecker::CheckCond(Expr *S) {
+  // Check test-expr for canonical form, save upper-bound UB, flags for
+  // less/greater and for strict/non-strict comparison.
+  // OpenMP [2.6] Canonical loop form. Test-expr may be one of the following:
+  //   var relational-op b
+  //   b relational-op var
+  //
+  if (!S) {
+    SemaRef.Diag(DefaultLoc, diag::err_omp_loop_not_canonical_cond) << Var;
+    return true;
+  }
+  S = S->IgnoreParenImpCasts();
+  SourceLocation CondLoc = S->getLocStart();
+  if (auto BO = dyn_cast<BinaryOperator>(S)) {
+    if (BO->isRelationalOp()) {
+      if (GetInitVarDecl(BO->getLHS()) == Var)
+        return SetUB(BO->getRHS(),
+                     (BO->getOpcode() == BO_LT || BO->getOpcode() == BO_LE),
+                     (BO->getOpcode() == BO_LT || BO->getOpcode() == BO_GT),
+                     BO->getSourceRange(), BO->getOperatorLoc());
+      if (GetInitVarDecl(BO->getRHS()) == Var)
+        return SetUB(BO->getLHS(),
+                     (BO->getOpcode() == BO_GT || BO->getOpcode() == BO_GE),
+                     (BO->getOpcode() == BO_LT || BO->getOpcode() == BO_GT),
+                     BO->getSourceRange(), BO->getOperatorLoc());
+    }
+  } else if (auto CE = dyn_cast<CXXOperatorCallExpr>(S)) {
+    if (CE->getNumArgs() == 2) {
+      auto Op = CE->getOperator();
+      switch (Op) {
+      case OO_Greater:
+      case OO_GreaterEqual:
+      case OO_Less:
+      case OO_LessEqual:
+        if (GetInitVarDecl(CE->getArg(0)) == Var)
+          return SetUB(CE->getArg(1), Op == OO_Less || Op == OO_LessEqual,
+                       Op == OO_Less || Op == OO_Greater, CE->getSourceRange(),
+                       CE->getOperatorLoc());
+        if (GetInitVarDecl(CE->getArg(1)) == Var)
+          return SetUB(CE->getArg(0), Op == OO_Greater || Op == OO_GreaterEqual,
+                       Op == OO_Less || Op == OO_Greater, CE->getSourceRange(),
+                       CE->getOperatorLoc());
+        break;
+      default:
+        break;
+      }
+    }
+  }
+  SemaRef.Diag(CondLoc, diag::err_omp_loop_not_canonical_cond)
+      << S->getSourceRange() << Var;
+  return true;
+}
+
+bool OpenMPIterationSpaceChecker::CheckIncRHS(Expr *RHS) {
+  // RHS of canonical loop form increment can be:
+  //   var + incr
+  //   incr + var
+  //   var - incr
+  //
+  RHS = RHS->IgnoreParenImpCasts();
+  if (auto BO = dyn_cast<BinaryOperator>(RHS)) {
+    if (BO->isAdditiveOp()) {
+      bool IsAdd = BO->getOpcode() == BO_Add;
+      if (GetInitVarDecl(BO->getLHS()) == Var)
+        return SetStep(BO->getRHS(), !IsAdd);
+      if (IsAdd && GetInitVarDecl(BO->getRHS()) == Var)
+        return SetStep(BO->getLHS(), false);
+    }
+  } else if (auto CE = dyn_cast<CXXOperatorCallExpr>(RHS)) {
+    bool IsAdd = CE->getOperator() == OO_Plus;
+    if ((IsAdd || CE->getOperator() == OO_Minus) && CE->getNumArgs() == 2) {
+      if (GetInitVarDecl(CE->getArg(0)) == Var)
+        return SetStep(CE->getArg(1), !IsAdd);
+      if (IsAdd && GetInitVarDecl(CE->getArg(1)) == Var)
+        return SetStep(CE->getArg(0), false);
+    }
+  }
+  SemaRef.Diag(RHS->getLocStart(), diag::err_omp_loop_not_canonical_incr)
+      << RHS->getSourceRange() << Var;
+  return true;
+}
+
+bool OpenMPIterationSpaceChecker::CheckInc(Expr *S) {
+  // Check incr-expr for canonical loop form and return true if it
+  // does not conform.
+  // OpenMP [2.6] Canonical loop form. Test-expr may be one of the following:
+  //   ++var
+  //   var++
+  //   --var
+  //   var--
+  //   var += incr
+  //   var -= incr
+  //   var = var + incr
+  //   var = incr + var
+  //   var = var - incr
+  //
+  if (!S) {
+    SemaRef.Diag(DefaultLoc, diag::err_omp_loop_not_canonical_incr) << Var;
+    return true;
+  }
+  S = S->IgnoreParens();
+  if (auto UO = dyn_cast<UnaryOperator>(S)) {
+    if (UO->isIncrementDecrementOp() && GetInitVarDecl(UO->getSubExpr()) == Var)
+      return SetStep(
+          SemaRef.ActOnIntegerConstant(UO->getLocStart(),
+                                       (UO->isDecrementOp() ? -1 : 1)).get(),
+          false);
+  } else if (auto BO = dyn_cast<BinaryOperator>(S)) {
+    switch (BO->getOpcode()) {
+    case BO_AddAssign:
+    case BO_SubAssign:
+      if (GetInitVarDecl(BO->getLHS()) == Var)
+        return SetStep(BO->getRHS(), BO->getOpcode() == BO_SubAssign);
+      break;
+    case BO_Assign:
+      if (GetInitVarDecl(BO->getLHS()) == Var)
+        return CheckIncRHS(BO->getRHS());
+      break;
+    default:
+      break;
+    }
+  } else if (auto CE = dyn_cast<CXXOperatorCallExpr>(S)) {
+    switch (CE->getOperator()) {
+    case OO_PlusPlus:
+    case OO_MinusMinus:
+      if (GetInitVarDecl(CE->getArg(0)) == Var)
+        return SetStep(
+            SemaRef.ActOnIntegerConstant(
+                        CE->getLocStart(),
+                        ((CE->getOperator() == OO_MinusMinus) ? -1 : 1)).get(),
+            false);
+      break;
+    case OO_PlusEqual:
+    case OO_MinusEqual:
+      if (GetInitVarDecl(CE->getArg(0)) == Var)
+        return SetStep(CE->getArg(1), CE->getOperator() == OO_MinusEqual);
+      break;
+    case OO_Equal:
+      if (GetInitVarDecl(CE->getArg(0)) == Var)
+        return CheckIncRHS(CE->getArg(1));
+      break;
+    default:
+      break;
+    }
+  }
+  SemaRef.Diag(S->getLocStart(), diag::err_omp_loop_not_canonical_incr)
+      << S->getSourceRange() << Var;
+  return true;
+}
+}
+
+/// \brief Called on a for stmt to check and extract its iteration space
+/// for further processing (such as collapsing).
+static bool CheckOpenMPIterationSpace(OpenMPDirectiveKind DKind, Stmt *S,
+                                      Sema &SemaRef, DSAStackTy &DSA) {
+  // OpenMP [2.6, Canonical Loop Form]
+  //   for (init-expr; test-expr; incr-expr) structured-block
+  auto For = dyn_cast_or_null<ForStmt>(S);
+  if (!For) {
+    SemaRef.Diag(S->getLocStart(), diag::err_omp_not_for)
+        << getOpenMPDirectiveName(DKind);
+    return true;
+  }
+  assert(For->getBody());
+
+  OpenMPIterationSpaceChecker ISC(SemaRef, For->getForLoc());
+
+  // Check init.
+  Stmt *Init = For->getInit();
+  if (ISC.CheckInit(Init)) {
+    return true;
+  }
+
+  bool HasErrors = false;
+
+  // Check loop variable's type.
+  VarDecl *Var = ISC.GetLoopVar();
+
+  // OpenMP [2.6, Canonical Loop Form]
+  // Var is one of the following:
+  //   A variable of signed or unsigned integer type.
+  //   For C++, a variable of a random access iterator type.
+  //   For C, a variable of a pointer type.
+  QualType VarType = Var->getType();
+  if (!VarType->isDependentType() && !VarType->isIntegerType() &&
+      !VarType->isPointerType() &&
+      !(SemaRef.getLangOpts().CPlusPlus && VarType->isOverloadableType())) {
+    SemaRef.Diag(Init->getLocStart(), diag::err_omp_loop_variable_type)
+        << SemaRef.getLangOpts().CPlusPlus;
+    HasErrors = true;
+  }
+
+  // OpenMP [2.14.1.1, Data-sharing Attribute Rules for Variables Referenced in
+  // a Construct, C/C++].
+  // The loop iteration variable(s) in the associated for-loop(s) of a for or
+  // parallel for construct may be listed in a private or lastprivate clause.
+  DSAStackTy::DSAVarData DVar = DSA.getTopDSA(Var);
+  if (DVar.CKind != OMPC_unknown && DVar.CKind != OMPC_linear &&
+      DVar.CKind != OMPC_threadprivate) {
+    // The loop iteration variable in the associated for-loop of a simd
+    // construct with just one associated for-loop may be listed in a linear
+    // clause with a constant-linear-step that is the increment of the
+    // associated for-loop.
+    // FIXME: allow OMPC_lastprivate when it is ready.
+    assert(DKind == OMPD_simd && "DSA for non-simd loop vars");
+    SemaRef.Diag(Init->getLocStart(), diag::err_omp_loop_var_dsa)
+        << getOpenMPClauseName(DVar.CKind);
+    if (DVar.RefExpr)
+      SemaRef.Diag(DVar.RefExpr->getExprLoc(), diag::note_omp_explicit_dsa)
+          << getOpenMPClauseName(DVar.CKind);
+    else
+      SemaRef.Diag(Var->getLocation(), diag::note_omp_predetermined_dsa)
+          << getOpenMPClauseName(DVar.CKind);
+    HasErrors = true;
+  } else {
+    // Make the loop iteration variable private by default.
+    DSA.addDSA(Var, nullptr, OMPC_private);
+  }
+
+  // Check test-expr.
+  HasErrors |= ISC.CheckCond(For->getCond());
+
+  // Check incr-expr.
+  HasErrors |= ISC.CheckInc(For->getInc());
+
+  if (ISC.Dependent())
+    return false;
+
+  return HasErrors;
+}
+
+/// \brief A helper routine to skip no-op (attributed, compound) stmts get the
+/// next nested for loop. If \a IgnoreCaptured is true, it skips captured stmt
+/// to get the first for loop.
+static Stmt *IgnoreContainerStmts(Stmt *S, bool IgnoreCaptured) {
+  if (IgnoreCaptured)
+    if (auto CapS = dyn_cast_or_null<CapturedStmt>(S))
+      S = CapS->getCapturedStmt();
+  // OpenMP [2.8.1, simd construct, Restrictions]
+  // All loops associated with the construct must be perfectly nested; that is,
+  // there must be no intervening code nor any OpenMP directive between any two
+  // loops.
+  while (true) {
+    if (auto AS = dyn_cast_or_null<AttributedStmt>(S))
+      S = AS->getSubStmt();
+    else if (auto CS = dyn_cast_or_null<CompoundStmt>(S)) {
+      if (CS->size() != 1)
+        break;
+      S = CS->body_back();
+    } else
+      break;
+  }
+  return S;
+}
+
+/// \brief Called on a for stmt to check itself and nested loops (if any).
+static bool CheckOpenMPLoop(OpenMPDirectiveKind DKind, unsigned NestedLoopCount,
+                            Stmt *AStmt, Sema &SemaRef, DSAStackTy &DSA) {
+  // This is helper routine for loop directives (e.g., 'for', 'simd',
+  // 'for simd', etc.).
+  assert(NestedLoopCount == 1);
+  Stmt *CurStmt = IgnoreContainerStmts(AStmt, true);
+  for (unsigned Cnt = 0; Cnt < NestedLoopCount; ++Cnt) {
+    if (CheckOpenMPIterationSpace(DKind, CurStmt, SemaRef, DSA))
+      return true;
+    // Move on to the next nested for loop, or to the loop body.
+    CurStmt = IgnoreContainerStmts(cast<ForStmt>(CurStmt)->getBody(), false);
+  }
+
+  // FIXME: Build resulting iteration space for IR generation (collapsing
+  // iteration spaces when loop count > 1 ('collapse' clause)).
+  return false;
+}
+
 StmtResult Sema::ActOnOpenMPSimdDirective(ArrayRef<OMPClause *> Clauses,
                                           Stmt *AStmt, SourceLocation StartLoc,
                                           SourceLocation EndLoc) {
-  Stmt *CStmt = AStmt;
-  while (CapturedStmt *CS = dyn_cast_or_null<CapturedStmt>(CStmt))
-    CStmt = CS->getCapturedStmt();
-  while (AttributedStmt *AS = dyn_cast_or_null<AttributedStmt>(CStmt))
-    CStmt = AS->getSubStmt();
-  ForStmt *For = dyn_cast<ForStmt>(CStmt);
-  if (!For) {
-    Diag(CStmt->getLocStart(), diag::err_omp_not_for)
-        << getOpenMPDirectiveName(OMPD_simd);
+  // In presence of clause 'collapse', it will define the nested loops number.
+  // For now, pass default value of 1.
+  if (CheckOpenMPLoop(OMPD_simd, 1, AStmt, *this, *DSAStack))
     return StmtError();
-  }
-
-  // FIXME: Checking loop canonical form, collapsing etc.
 
   getCurFunction()->setHasBranchProtectedScope();
   return OMPSimdDirective::Create(Context, StartLoc, EndLoc, Clauses, AStmt);
 }
 
 OMPClause *Sema::ActOnOpenMPSingleExprClause(OpenMPClauseKind Kind, Expr *Expr,
                                              SourceLocation StartLoc,
                                              SourceLocation LParenLoc,
                                              SourceLocation EndLoc) {
   OMPClause *Res = nullptr;
   switch (Kind) {
   case OMPC_if:
     Res = ActOnOpenMPIfClause(Expr, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_num_threads:
     Res = ActOnOpenMPNumThreadsClause(Expr, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_safelen:
     Res = ActOnOpenMPSafelenClause(Expr, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_collapse:
     Res = ActOnOpenMPCollapseClause(Expr, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_default:
   case OMPC_proc_bind:
   case OMPC_private:
   case OMPC_firstprivate:
   case OMPC_shared:
   case OMPC_linear:
   case OMPC_aligned:
   case OMPC_copyin:
   case OMPC_threadprivate:
   case OMPC_unknown:
     llvm_unreachable("Clause is not allowed.");
   }
   return Res;
 }
 
 OMPClause *Sema::ActOnOpenMPIfClause(Expr *Condition, SourceLocation StartLoc,
                                      SourceLocation LParenLoc,
                                      SourceLocation EndLoc) {
   Expr *ValExpr = Condition;
   if (!Condition->isValueDependent() && !Condition->isTypeDependent() &&
       !Condition->isInstantiationDependent() &&
       !Condition->containsUnexpandedParameterPack()) {
     ExprResult Val = ActOnBooleanCondition(DSAStack->getCurScope(),
                                            Condition->getExprLoc(), Condition);
     if (Val.isInvalid())
       return nullptr;
 
     ValExpr = Val.get();
   }
 
   return new (Context) OMPIfClause(ValExpr, StartLoc, LParenLoc, EndLoc);
 }
 
 ExprResult Sema::PerformImplicitIntegerConversion(SourceLocation Loc,
                                                   Expr *Op) {
   if (!Op)
     return ExprError();
 
   class IntConvertDiagnoser : public ICEConvertDiagnoser {
   public:
     IntConvertDiagnoser()
         : ICEConvertDiagnoser(/*AllowScopedEnumerations*/ false, false, true) {}
     SemaDiagnosticBuilder diagnoseNotInt(Sema &S, SourceLocation Loc,
                                          QualType T) override {
       return S.Diag(Loc, diag::err_omp_not_integral) << T;
     }
     SemaDiagnosticBuilder diagnoseIncomplete(Sema &S, SourceLocation Loc,
                                              QualType T) override {
       return S.Diag(Loc, diag::err_omp_incomplete_type) << T;
     }
     SemaDiagnosticBuilder diagnoseExplicitConv(Sema &S, SourceLocation Loc,
                                                QualType T,
                                                QualType ConvTy) override {
       return S.Diag(Loc, diag::err_omp_explicit_conversion) << T << ConvTy;
     }
     SemaDiagnosticBuilder noteExplicitConv(Sema &S, CXXConversionDecl *Conv,
                                            QualType ConvTy) override {
       return S.Diag(Conv->getLocation(), diag::note_omp_conversion_here)
              << ConvTy->isEnumeralType() << ConvTy;
     }
     SemaDiagnosticBuilder diagnoseAmbiguous(Sema &S, SourceLocation Loc,
                                             QualType T) override {
       return S.Diag(Loc, diag::err_omp_ambiguous_conversion) << T;
     }
     SemaDiagnosticBuilder noteAmbiguous(Sema &S, CXXConversionDecl *Conv,
                                         QualType ConvTy) override {
       return S.Diag(Conv->getLocation(), diag::note_omp_conversion_here)
              << ConvTy->isEnumeralType() << ConvTy;
     }
     SemaDiagnosticBuilder diagnoseConversion(Sema &, SourceLocation, QualType,
                                              QualType) override {
OMPClause *Sema::ActOnOpenMPSimpleClause(
     SourceLocation StartLoc, SourceLocation LParenLoc, SourceLocation EndLoc) {
   OMPClause *Res = nullptr;
   switch (Kind) {
   case OMPC_default:
     Res =
         ActOnOpenMPDefaultClause(static_cast<OpenMPDefaultClauseKind>(Argument),
                                  ArgumentLoc, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_proc_bind:
     Res = ActOnOpenMPProcBindClause(
         static_cast<OpenMPProcBindClauseKind>(Argument), ArgumentLoc, StartLoc,
         LParenLoc, EndLoc);
     break;
   case OMPC_if:
   case OMPC_num_threads:
   case OMPC_safelen:
   case OMPC_collapse:
   case OMPC_private:
   case OMPC_firstprivate:
   case OMPC_shared:
   case OMPC_linear:
   case OMPC_aligned:
   case OMPC_copyin:

lib/Sema/SemaStmt.cpp

 
 StmtResult
 Sema::ActOnBreakStmt(SourceLocation BreakLoc, Scope *CurScope) {
   Scope *S = CurScope->getBreakParent();
   if (!S) {
     // C99 6.8.6.3p1: A break shall appear only in or as a switch/loop body.
     return StmtError(Diag(BreakLoc, diag::err_break_not_in_loop_or_switch));
   }
+  if (S->isOpenMPLoopScope())
+    return StmtError(Diag(BreakLoc, diag::err_omp_loop_cannot_use_stmt)
+                     << "break");
 
   return new (Context) BreakStmt(BreakLoc);
 }
 
 /// \brief Determine whether the given expression is a candidate for
 /// copy elision in either a return statement or a throw expression.
 ///
 /// \param ReturnType If we're determining the copy elision candidate for

 /// handlers and creates a try statement from them.
 StmtResult Sema::ActOnCXXTryBlock(SourceLocation TryLoc, Stmt *TryBlock,
                                   ArrayRef<Stmt *> Handlers) {
   // Don't report an error if 'try' is used in system headers.
   if (!getLangOpts().CXXExceptions &&
       !getSourceManager().isInSystemHeader(TryLoc))
       Diag(TryLoc, diag::err_exceptions_disabled) << "try";
 
+  if (getCurScope() && getCurScope()->isOpenMPSimdNestedScope())
+    Diag(TryLoc, diag::err_omp_simd_region_cannot_use_stmt) << "try";
+
   const unsigned NumHandlers = Handlers.size();
   assert(NumHandlers > 0 &&
          "The parser shouldn't call this if there are no handlers.");
 
   SmallVector<TypeWithHandler, 8> TypesWithHandlers;
 
   for (unsigned i = 0; i < NumHandlers; ++i) {
     CXXCatchStmt *Handler = cast<CXXCatchStmt>(Handlers[i]);

test/OpenMP/simd_loop_messages.cpp

+// RUN: %clang_cc1 -fsyntax-only -fopenmp=libiomp5 -x c++ -std=c++11 -fexceptions -fcxx-exceptions -verify %s
+
+static int sii;
+#pragma omp threadprivate(sii)
+
+int test_iteration_spaces() {
+  const int N = 100;
+  float a[N], b[N], c[N];
+  int ii, jj, kk;
+  float fii;
+  double dii;
+  #pragma omp simd
+  for (int i = 0; i < 10; i+=1) {
+    c[i] = a[i] + b[i];
+  }
+  #pragma omp simd
+  for (char i = 0; i < 10; i++) {
+    c[i] = a[i] + b[i];
+  }
+  #pragma omp simd
+  for (char i = 0; i < 10; i+='\1') {
+    c[i] = a[i] + b[i];
+  }
+  #pragma omp simd
+  for (long long i = 0; i < 10; i++) {
+    c[i] = a[i] + b[i];
+  }
+  // expected-error@+2 {{expression must have integral or unscoped enumeration type, not 'double'}}
+  #pragma omp simd
+  for (long long i = 0; i < 10; i+=1.5) {
+    c[i] = a[i] + b[i];
+  }
+  #pragma omp simd
+  for (long long i = 0; i < 'z'; i+=1u) {
+    c[i] = a[i] + b[i];
+  }
+  // expected-error@+2 {{variable must be of integer or random access iterator type}}
+  #pragma omp simd
+  for (float fi = 0; fi < 10.0; fi++) {
+    c[(int)fi] = a[(int)fi] + b[(int)fi];
+  }
+  // expected-error@+2 {{variable must be of integer or random access iterator type}}
+  #pragma omp simd
+  for (double fi = 0; fi < 10.0; fi++) {
+    c[(int)fi] = a[(int)fi] + b[(int)fi];
+  }
+  // expected-error@+2 {{variable must be of integer or random access iterator type}}
+  #pragma omp simd
+  for (int &ref = ii; ref < 10; ref++) {
+  }
+  // expected-error@+2 {{initialization clause of OpenMP for loop must be of the form 'var = init' or 'T var = init'}}
+  #pragma omp simd
+  for (int i; i < 10; i++)
+    c[i] = a[i];
+
+  // expected-error@+2 {{initialization clause of OpenMP for loop must be of the form 'var = init' or 'T var = init'}}
+  #pragma omp simd
+  for (int i = 0, j = 0; i < 10; ++i)
+    c[i] = a[i];
+
+  // expected-error@+2 {{initialization clause of OpenMP for loop must be of the form 'var = init' or 'T var = init'}}
+  #pragma omp simd
+  for (;ii < 10; ++ii)
+    c[ii] = a[ii];
+
+  // expected-warning@+3 {{expression result unused}}
+  // expected-error@+2 {{initialization clause of OpenMP for loop must be of the form 'var = init' or 'T var = init'}}
+  #pragma omp simd
+  for (ii + 1;ii < 10; ++ii)
+    c[ii] = a[ii];
+
+  // expected-error@+2 {{initialization clause of OpenMP for loop must be of the form 'var = init' or 'T var = init'}}
+  #pragma omp simd
+  for (c[ii] = 0;ii < 10; ++ii)
+    c[ii] = a[ii];
+
+  // Ok to skip parenthesises.
+  #pragma omp simd
+  for (((ii)) = 0;ii < 10; ++ii)
+    c[ii] = a[ii];
+
+  // expected-error@+2 {{condition of OpenMP for loop must be a relational comparison ('<', '<=', '>', or '>=') of loop variable 'i'}}
+  #pragma omp simd
+  for (int i = 0; i; i++)
+    c[i] = a[i];
+
+  // expected-error@+3 {{condition of OpenMP for loop must be a relational comparison ('<', '<=', '>', or '>=') of loop variable 'i'}}
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'i'}}
+  #pragma omp simd
+  for (int i = 0; jj < kk; ii++)
+    c[i] = a[i];
+
+  // expected-error@+2 {{condition of OpenMP for loop must be a relational comparison ('<', '<=', '>', or '>=') of loop variable 'i'}}
+  #pragma omp simd
+  for (int i = 0; !!i; i++)
+    c[i] = a[i];
+
+  // expected-error@+2 {{condition of OpenMP for loop must be a relational comparison ('<', '<=', '>', or '>=') of loop variable 'i'}}
+  #pragma omp simd
+  for (int i = 0; i != 1; i++)
+    c[i] = a[i];
+
+  // expected-error@+2 {{condition of OpenMP for loop must be a relational comparison ('<', '<=', '>', or '>=') of loop variable 'i'}}
+  #pragma omp simd
+  for (int i = 0; ; i++)
+    c[i] = a[i];
+
+  // Ok.
+  #pragma omp simd
+  for (int i = 11; i > 10; i--)
+    c[i] = a[i];
+
+  // Ok.
+  #pragma omp simd
+  for (int i = 0; i < 10; ++i)
+    c[i] = a[i];
+
+    // Ok.
+  #pragma omp simd
+  for (ii = 0; ii < 10; ++ii)
+    c[ii] = a[ii];
+
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'ii'}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; ++jj)
+    c[ii] = a[jj];
+
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'ii'}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; ++ ++ ii)
+    c[ii] = a[ii];
+
+  // Ok but undefined behavior (in general, cannot check that incr
+  // is really loop-invariant).
+  #pragma omp simd
+  for (ii = 0; ii < 10; ii = ii + ii)
+    c[ii] = a[ii];
+
+  // expected-error@+2 {{expression must have integral or unscoped enumeration type, not 'float'}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; ii = ii + 1.0f)
+    c[ii] = a[ii];
+
+  // Ok - step was converted to integer type.
+  #pragma omp simd
+  for (ii = 0; ii < 10; ii = ii + (int)1.1f)
+    c[ii] = a[ii];
+
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'ii'}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; jj = ii + 2)
+    c[ii] = a[ii];
+
+  // expected-warning@+3 {{relational comparison result unused}}
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'ii'}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; jj > kk + 2)
+    c[ii] = a[ii];
+
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'ii'}}
+  #pragma omp simd
+  for (ii = 0; ii < 10;)
+    c[ii] = a[ii];
+
+  // expected-warning@+3 {{expression result unused}}
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'ii'}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; !ii)
+    c[ii] = a[ii];
+
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'ii'}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; ii ? ++ii : ++jj)
+    c[ii] = a[ii];
+
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'ii'}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; ii = ii < 10)
+    c[ii] = a[ii];
+
+  // expected-note@+3 {{loop step is expected to be positive due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'ii' to increase on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; ii = ii + 0)
+    c[ii] = a[ii];
+
+  // expected-note@+3 {{loop step is expected to be positive due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'ii' to increase on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; ii = ii + (int)(0.8 - 0.45))
+    c[ii] = a[ii];
+
+  // expected-note@+3 {{loop step is expected to be positive due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'ii' to increase on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (ii = 0; (ii) < 10; ii-=25)
+    c[ii] = a[ii];
+
+  // expected-note@+3 {{loop step is expected to be positive due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'ii' to increase on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (ii = 0; (ii < 10); ii-=0)
+    c[ii] = a[ii];
+
+  // expected-note@+3 {{loop step is expected to be negative due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'ii' to decrease on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (ii = 0; ii > 10; (ii+=0))
+    c[ii] = a[ii];
+
+  // expected-note@+3 {{loop step is expected to be positive due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'ii' to increase on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (ii = 0; ii < 10; (ii) = (1-1)+(ii))
+    c[ii] = a[ii];
+
+  // expected-note@+3 {{loop step is expected to be negative due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'ii' to decrease on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for ((ii = 0); ii > 10; (ii-=0))
+    c[ii] = a[ii];
+
+  // expected-note@+3 {{loop step is expected to be positive due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'ii' to increase on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (ii = 0; (ii < 10); (ii-=0))
+    c[ii] = a[ii];
+
+  // expected-note@+2  {{defined as private}}
+  // expected-error@+2 {{loop iteration variable may not be private}}
+  #pragma omp simd private(ii)
+  for (ii = 0; ii < 10; ii++)
+    c[ii] = a[ii];
+
+  // expected-error@+3 {{unexpected OpenMP clause 'shared' in directive '#pragma omp simd'}}
+  // expected-note@+2  {{defined as shared}}
+  // expected-error@+2 {{loop iteration variable may not be shared}}
+  #pragma omp simd shared(ii)
+  for (ii = 0; ii < 10; ii++)
+    c[ii] = a[ii];
+
+  #pragma omp simd linear(ii)
+  for (ii = 0; ii < 10; ii++)
+    c[ii] = a[ii];
+
+  // TODO: Add test for lastprivate.
+
+  #pragma omp parallel
+  {
+    #pragma omp simd
+    for (sii = 0; sii < 10; sii+=1)
+      c[sii] = a[sii];
+  }
+
+  // expected-error@+2 {{statement after '#pragma omp simd' must be a for loop}}
+  #pragma omp simd
+  for (auto &item : a) {
+    item = item + 1;
+  }
+
+  // expected-note@+3 {{loop step is expected to be positive due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'i' to increase on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (unsigned i = 9; i < 10; i--) {
+    c[i] = a[i] + b[i];
+  }
+
+  int (*lb)[4] = nullptr;
+  #pragma omp simd
+  for (int (*p)[4] = lb; p < lb + 8; ++p) {
+  }
+
+  // expected-warning@+2 {{initialization clause of OpenMP for loop is not in canonical form ('var = init' or 'T var = init')}}
+  #pragma omp simd
+  for (int a{0}; a<10; ++a) {
+  }
+  return 0;
+}
+
+// Iterators allowed in openmp for-loops.
+namespace std {
+struct random_access_iterator_tag { };
+template <class Iter> struct iterator_traits {
+  typedef typename Iter::difference_type difference_type;
+  typedef typename Iter::iterator_category iterator_category;
+};
+template <class Iter>
+typename iterator_traits<Iter>::difference_type
+distance(Iter first, Iter last) { return first - last; }
+}
+class Iter0 {
+  public:
+    Iter0() { }
+    Iter0(const Iter0 &) { }
+    Iter0 operator ++() { return *this; }
+    Iter0 operator --() { return *this; }
+    bool operator <(Iter0 a) { return true; }
+};
+int operator -(Iter0 a, Iter0 b) { return 0; }
+class Iter1 {
+  public:
+    Iter1(float f=0.0f, double d=0.0) { }
+    Iter1(const Iter1 &) { }
+    Iter1 operator ++() { return *this; }
+    Iter1 operator --() { return *this; }
+    bool operator <(Iter1 a) { return true; }
+    bool operator >=(Iter1 a) { return false; }
+};
+class GoodIter {
+  public:
+    GoodIter() { }
+    GoodIter(const GoodIter &) { }
+    GoodIter(int fst, int snd) { }
+    GoodIter &operator =(const GoodIter &that) { return *this; }
+    GoodIter &operator =(const Iter0 &that) { return *this; }
+    GoodIter &operator +=(int x) { return *this; }
+    explicit GoodIter(void *) { }
+    GoodIter operator ++() { return *this; }
+    GoodIter operator --() { return *this; }
+    bool operator !() { return true; }
+    bool operator <(GoodIter a) { return true; }
+    bool operator <=(GoodIter a) { return true; }
+    bool operator >=(GoodIter a) { return false; }
+    typedef int difference_type;
+    typedef std::random_access_iterator_tag iterator_category;
+};
+int operator -(GoodIter a, GoodIter b) { return 0; }
+GoodIter operator -(GoodIter a) { return a; }
+GoodIter operator -(GoodIter a, int v) { return GoodIter(); }
+GoodIter operator +(GoodIter a, int v) { return GoodIter(); }
+GoodIter operator -(int v, GoodIter a) { return GoodIter(); }
+GoodIter operator +(int v, GoodIter a) { return GoodIter(); }
+
+int test_with_random_access_iterator() {
+  GoodIter begin, end;
+  Iter0 begin0, end0;
+  #pragma omp simd
+  for (GoodIter I = begin; I < end; ++I)
+    ++I;
+  // expected-error@+2 {{variable must be of integer or random access iterator type}}
+  #pragma omp simd
+  for (GoodIter &I = begin; I < end; ++I)
+    ++I;
+  #pragma omp simd
+  for (GoodIter I = begin; I >= end; --I)
+    ++I;
+  // expected-warning@+2 {{initialization clause of OpenMP for loop is not in canonical form ('var = init' or 'T var = init')}}
+  #pragma omp simd
+  for (GoodIter I(begin); I < end; ++I)
+    ++I;
+  // expected-warning@+2 {{initialization clause of OpenMP for loop is not in canonical form ('var = init' or 'T var = init')}}
+  #pragma omp simd
+  for (GoodIter I(nullptr); I < end; ++I)
+    ++I;
+  // expected-warning@+2 {{initialization clause of OpenMP for loop is not in canonical form ('var = init' or 'T var = init')}}
+  #pragma omp simd
+  for (GoodIter I(0); I < end; ++I)
+    ++I;
+  // expected-warning@+2 {{initialization clause of OpenMP for loop is not in canonical form ('var = init' or 'T var = init')}}
+  #pragma omp simd
+  for (GoodIter I(1,2); I < end; ++I)
+    ++I;
+  #pragma omp simd
+  for (begin = GoodIter(0); begin < end; ++begin)
+    ++begin;
+  #pragma omp simd
+  for (begin = begin0; begin < end; ++begin)
+    ++begin;
+  // expected-error@+2 {{initialization clause of OpenMP for loop must be of the form 'var = init' or 'T var = init'}}
+  #pragma omp simd
+  for (++begin; begin < end; ++begin)
+    ++begin;
+  #pragma omp simd
+  for (begin = end; begin < end; ++begin)
+    ++begin;
+  // expected-error@+2 {{condition of OpenMP for loop must be a relational comparison ('<', '<=', '>', or '>=') of loop variable 'I'}}
+  #pragma omp simd
+  for (GoodIter I = begin; I - I; ++I)
+    ++I;
+  // expected-error@+2 {{condition of OpenMP for loop must be a relational comparison ('<', '<=', '>', or '>=') of loop variable 'I'}}
+  #pragma omp simd
+  for (GoodIter I = begin; begin < end; ++I)
+    ++I;
+  // expected-error@+2 {{condition of OpenMP for loop must be a relational comparison ('<', '<=', '>', or '>=') of loop variable 'I'}}
+  #pragma omp simd
+  for (GoodIter I = begin; !I; ++I)
+    ++I;
+  // expected-note@+3 {{loop step is expected to be negative due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'I' to decrease on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (GoodIter I = begin; I >= end; I = I + 1)
+    ++I;
+  #pragma omp simd
+  for (GoodIter I = begin; I >= end; I = I - 1)
+    ++I;
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'I'}}
+  #pragma omp simd
+  for (GoodIter I = begin; I >= end; I = -I)
+    ++I;
+  // expected-note@+3 {{loop step is expected to be negative due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'I' to decrease on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (GoodIter I = begin; I >= end; I = 2 + I)
+    ++I;
+  // expected-error@+2 {{increment clause of OpenMP for loop must perform simple addition or subtraction on loop variable 'I'}}
+  #pragma omp simd
+  for (GoodIter I = begin; I >= end; I = 2 - I)
+    ++I;
+  #pragma omp simd
+  for (Iter0 I = begin0; I < end0; ++I)
+    ++I;
+  // Initializer is constructor without params.
+  // expected-warning@+2 {{initialization clause of OpenMP for loop is not in canonical form ('var = init' or 'T var = init')}}
+  #pragma omp simd
+  for (Iter0 I; I < end0; ++I)
+    ++I;
+  Iter1 begin1, end1;
+  #pragma omp simd
+  for (Iter1 I = begin1; I < end1; ++I)
+    ++I;
+  // expected-note@+3 {{loop step is expected to be negative due to this condition}}
+  // expected-error@+2 {{increment expression must cause 'I' to decrease on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (Iter1 I = begin1; I >= end1; ++I)
+    ++I;
+  // Initializer is constructor with all default params.
+  // expected-warning@+2 {{initialization clause of OpenMP for loop is not in canonical form ('var = init' or 'T var = init')}}
+  #pragma omp simd
+  for (Iter1 I; I < end1; ++I) {
+  }
+  return 0;
+}
+
+template <typename IT, int ST> class TC {
+  public:
+    int dotest_lt(IT begin, IT end) {
+      // expected-note@+3 {{loop step is expected to be positive due to this condition}}
+      // expected-error@+2 {{increment expression must cause 'I' to increase on each iteration of OpenMP for loop}}
+      #pragma omp simd
+      for (IT I = begin; I < end; I = I + ST) {
+        ++I;
+      }
+      // expected-note@+3 {{loop step is expected to be positive due to this condition}}
+      // expected-error@+2 {{increment expression must cause 'I' to increase on each iteration of OpenMP for loop}}
+      #pragma omp simd
+      for (IT I = begin; I <= end; I += ST) {
+        ++I;
+      }
+      #pragma omp simd
+      for (IT I = begin; I < end; ++I) {
+        ++I;
+      }
+    }
+
+    static IT step() {
+      return IT(ST);
+    }
+};
+template <typename IT, int ST=0> int dotest_gt(IT begin, IT end) {
+  // expected-note@+3 2 {{loop step is expected to be negative due to this condition}}
+  // expected-error@+2 2 {{increment expression must cause 'I' to decrease on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (IT I = begin; I >= end; I = I + ST) {
+    ++I;
+  }
+  // expected-note@+3 2 {{loop step is expected to be negative due to this condition}}
+  // expected-error@+2 2 {{increment expression must cause 'I' to decrease on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (IT I = begin; I >= end; I += ST) {
+    ++I;
+  }
+
+  // expected-note@+3 3 {{loop step is expected to be negative due to this condition}}
+  // expected-error@+2 3 {{increment expression must cause 'I' to decrease on each iteration of OpenMP for loop}}
+  #pragma omp simd
+  for (IT I = begin; I >= end; ++I) {
+    ++I;
+  }
+
+  #pragma omp simd
+  for (IT I = begin; I < end; I+=TC<int,ST>::step()) {
+    ++I;
+  }
+}
+
+void test_with_template() {
+  GoodIter begin, end;
+  TC<GoodIter, 100> t1;
+  TC<GoodIter, -100> t2;
+  t1.dotest_lt(begin, end);
+  t2.dotest_lt(begin, end); // expected-note {{in instantiation of member function 'TC<GoodIter, -100>::dotest_lt' requested here}}
+  dotest_gt(begin, end); // expected-note {{in instantiation of function template specialization 'dotest_gt<GoodIter, 0>' requested here}}
+  dotest_gt<unsigned, -10>(0, 100); // expected-note {{in instantiation of function template specialization 'dotest_gt<unsigned int, -10>' requested here}}
+}
+
+void test_loop_break() {
+  const int N = 100;
+  float a[N], b[N], c[N];
+  #pragma omp simd
+  for (int i = 0; i < 10; i++) {
+    c[i] = a[i] + b[i];
+    for (int j = 0; j < 10; ++j) {
+      if (a[i] > b[j])
+        break; // OK in nested loop
+    }
+    switch(i) {
+      case 1:
+        b[i]++;
+        break;
+      default:
+        break;
+    }
+    if (c[i] > 10)
+      break; // expected-error {{'break' statement cannot be used in OpenMP for loop}}
+
+    if (c[i] > 11)
+      break; // expected-error {{'break' statement cannot be used in OpenMP for loop}}
+  }
+
+  #pragma omp simd
+  for (int i = 0; i < 10; i++) {
+    for (int j = 0; j < 10; j++) {
+      c[i] = a[i] + b[i];
+      if (c[i] > 10) {
+        if (c[i] < 20) {
+          break; // OK
+        }
+      }
+    }
+  }
+}
+
+void test_loop_eh() {
+  const int N = 100;
+  float a[N], b[N], c[N];
+  #pragma omp simd
+  for (int i = 0; i < 10; i++) {
+    c[i] = a[i] + b[i];
+    try { // expected-error {{'try' statement cannot be used in OpenMP simd region}}
+      for (int j = 0; j < 10; ++j) {
+        if (a[i] > b[j])
+          throw a[i]; // expected-error {{'throw' statement cannot be used in OpenMP simd region}}
+      }
+      throw a[i]; // expected-error {{'throw' statement cannot be used in OpenMP simd region}}
+    }
+    catch (float f) {
+      if (f > 0.1)
+        throw a[i]; // expected-error {{'throw' statement cannot be used in OpenMP simd region}}
+      return; // expected-error {{cannot return from OpenMP region}}
+    }
+    switch(i) {
+      case 1:
+        b[i]++;
+        break;
+      default:
+        break;
+    }
+    for (int j = 0; j < 10; j++) {
+      if (c[i] > 10)
+        throw c[i]; // expected-error {{'throw' statement cannot be used in OpenMP simd region}}
+    }
+  }
+  if (c[9] > 10)
+    throw c[9]; // OK
+}
+

test/OpenMP/simd_misc_messages.c

void test_firstprivate()
   int i;
   // expected-error@+3 {{expected ')'}} expected-note@+3 {{to match this '('}}
   // expected-error@+2 {{unexpected OpenMP clause 'firstprivate' in directive '#pragma omp simd'}}
   // expected-error@+1 {{expected expression}}
   #pragma omp simd firstprivate(
   for (i = 0; i < 16; ++i) ;
 }
 
+void test_loop_messages()
+{
+  float a[100], b[100], c[100];
+  // expected-error@+2 {{variable must be of integer or pointer type}}
+  #pragma omp simd
+  for (float fi = 0; fi < 10.0; fi++) {
+    c[(int)fi] = a[(int)fi] + b[(int)fi];
+  }
+  // expected-error@+2 {{variable must be of integer or pointer type}}
+  #pragma omp simd
+  for (double fi = 0; fi < 10.0; fi++) {
+    c[(int)fi] = a[(int)fi] + b[(int)fi];
+  }
+}
+