[OpenMP] Allow negative lower bound in array sections based on pointers

OpenMP 4.5 removed the restriction that array section lower bound must be non negative.
This change is to allow negative values for array section based on pointers.
For array section based on array type there is still a restriction: "The array section must be a subset of the original array."

Patch by David S.

Differential Revision: https://reviews.llvm.org/D22481

llvm-svn: 276177

1 files changed, 9 insertions, 10 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index d748b3c18e5..ac5da811299 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -4304,14 +4304,13 @@ ExprResult Sema::ActOnOMPArraySectionExpr(Expr *Base, SourceLocation LBLoc,
                           diag::err_omp_section_incomplete_type, Base))
     return ExprError();
 
-  if (LowerBound) {
+  if (LowerBound && !OriginalTy->isAnyPointerType()) {
     llvm::APSInt LowerBoundValue;
     if (LowerBound->EvaluateAsInt(LowerBoundValue, Context)) {
-      // OpenMP 4.0, [2.4 Array Sections]
-      // The lower-bound and length must evaluate to non-negative integers.
+      // OpenMP 4.5, [2.4 Array Sections]
+      // The array section must be a subset of the original array.
       if (LowerBoundValue.isNegative()) {
-        Diag(LowerBound->getExprLoc(), diag::err_omp_section_negative)
-            << 0 << LowerBoundValue.toString(/*Radix=*/10, /*Signed=*/true)
+        Diag(LowerBound->getExprLoc(), diag::err_omp_section_not_subset_of_array)
             << LowerBound->getSourceRange();
         return ExprError();
       }
@@ -4321,11 +4320,11 @@ ExprResult Sema::ActOnOMPArraySectionExpr(Expr *Base, SourceLocation LBLoc,
   if (Length) {
     llvm::APSInt LengthValue;
     if (Length->EvaluateAsInt(LengthValue, Context)) {
-      // OpenMP 4.0, [2.4 Array Sections]
-      // The lower-bound and length must evaluate to non-negative integers.
+      // OpenMP 4.5, [2.4 Array Sections]
+      // The length must evaluate to non-negative integers.
       if (LengthValue.isNegative()) {
-        Diag(Length->getExprLoc(), diag::err_omp_section_negative)
-            << 1 << LengthValue.toString(/*Radix=*/10, /*Signed=*/true)
+        Diag(Length->getExprLoc(), diag::err_omp_section_length_negative)
+            << LengthValue.toString(/*Radix=*/10, /*Signed=*/true)
             << Length->getSourceRange();
         return ExprError();
       }
@@ -4333,7 +4332,7 @@ ExprResult Sema::ActOnOMPArraySectionExpr(Expr *Base, SourceLocation LBLoc,
   } else if (ColonLoc.isValid() &&
              (OriginalTy.isNull() || (!OriginalTy->isConstantArrayType() &&
                                       !OriginalTy->isVariableArrayType()))) {
-    // OpenMP 4.0, [2.4 Array Sections]
+    // OpenMP 4.5, [2.4 Array Sections]
     // When the size of the array dimension is not known, the length must be
     // specified explicitly.
     Diag(ColonLoc, diag::err_omp_section_length_undefined)