[OPENMP]Fix PR48387: disable warning messages caused by internal conversions.

[ABataev]

Summary

Compiler needs to convert some of the loop iteration
variables/conditions to different types for better codegen and it may
lead to spurious warning messages about implicit signed/unsigned
conversions.

[jdoerfert]

LGTM.

clang/lib/Sema/SemaOpenMP.cpp

if (CaptureExpr->getObjectKind() == OK_Ordinary && CaptureExpr->isGLValue()) {
     }
     WithInit = true;
   }
   auto *CED = OMPCapturedExprDecl::Create(C, S.CurContext, Id, Ty,
                                           CaptureExpr->getBeginLoc());
   if (!WithInit)
     CED->addAttr(OMPCaptureNoInitAttr::CreateImplicit(C));
   S.CurContext->addHiddenDecl(CED);
+  Sema::TentativeAnalysisScope Trap(S);
   S.AddInitializerToDecl(CED, Init, /*DirectInit=*/false);
   return CED;
 }
 
 static DeclRefExpr *buildCapture(Sema &S, ValueDecl *D, Expr *CaptureExpr,
                                  bool WithInit) {
   OMPCapturedExprDecl *CD;
   if (VarDecl *VD = S.isOpenMPCapturedDecl(D))
std::pair<Expr *, Expr *> OpenMPIterationSpaceChecker::buildMinMaxValues(
   // Convert to the original type.
   if (SemaRef.Context.hasSameType(Diff.get()->getType(), VarType))
     Diff = SemaRef.PerformImplicitConversion(Diff.get(), VarType,
                                              Sema::AA_Converting,
                                              /*AllowExplicit=*/true);
   if (!Diff.isUsable())
     return std::make_pair(nullptr, nullptr);
 
+  Sema::TentativeAnalysisScope Trap(SemaRef);
   Diff = SemaRef.ActOnFinishFullExpr(Diff.get(), /*DiscardedValue=*/false);
   if (!Diff.isUsable())
     return std::make_pair(nullptr, nullptr);
 
   if (TestIsLessOp.getValue())
     MaxExpr = Diff.get();
   else
     MinExpr = Diff.get();

clang/test/OpenMP/for_ast_print.cpp

-// RUN: %clang_cc1 -verify -fopenmp -ast-print %s | FileCheck %s
+// RUN: %clang_cc1 -verify -fopenmp -ast-print %s -Wsign-conversion | FileCheck %s
 // RUN: %clang_cc1 -fopenmp -x c++ -std=c++11 -emit-pch -o %t %s
 // RUN: %clang_cc1 -fopenmp -std=c++11 -include-pch %t -fsyntax-only -verify %s -ast-print | FileCheck %s
 
-// RUN: %clang_cc1 -verify -fopenmp-simd -ast-print %s | FileCheck %s
+// RUN: %clang_cc1 -verify -fopenmp-simd -ast-print %s -Wsign-conversion | FileCheck %s
 // RUN: %clang_cc1 -fopenmp-simd -x c++ -std=c++11 -emit-pch -o %t %s
 // RUN: %clang_cc1 -fopenmp-simd -std=c++11 -include-pch %t -fsyntax-only -verify %s -ast-print | FileCheck %s
 // expected-no-diagnostics
 
 #ifndef HEADER
 #define HEADER
 
 void foo() {}

 int main(int argc, char **argv) {
 // CHECK: int main(int argc, char **argv) {
   int b = argc, c, d, e, f, g;
   float arr[20];
   static int a;
 // CHECK: static int a;
 #pragma omp for schedule(guided, argc) reduction(+:argv[0][:1]) order(concurrent)
   // CHECK-NEXT: #pragma omp for schedule(guided, argc) reduction(+: argv[0][:1]) order(concurrent)
-  for (int i = 0; i < 2; ++i)
+  for (int i = argc; i < c; ++i)
     a = 2;
-// CHECK-NEXT: for (int i = 0; i < 2; ++i)
+// CHECK-NEXT: for (int i = argc; i < c; ++i)
 // CHECK-NEXT: a = 2;
 #pragma omp parallel
 #pragma omp for private(argc, b), firstprivate(argv, c), lastprivate(d, f) collapse(3) schedule(auto) ordered nowait linear(g:-1) reduction(task, +:e)
   for (int i = 0; i < 10; ++i)
     for (int j = 0; j < 10; ++j)
       for (auto x : arr)
         foo(), (void)x;
   // CHECK-NEXT: #pragma omp parallel