[PATCH] D91348: [OpenCL] Warn about side effects for unevaluated vec_step arg

[Sven van Haastregt via Phabricator via cfe-commits]

svenvh created this revision.
svenvh added a reviewer: Anastasia.
Herald added a subscriber: yaxunl.
Herald added a project: clang.
svenvh requested review of this revision.

The argument to the `vec_step` builtin is not evaluated.  Hoist the
diagnostic for this in `Sema::CheckUnaryExprOrTypeTraitOperand` such
that it comes before `Sema::CheckVecStepTraitOperandType`.

A minor side-effect of this change is that it also produces the
warning for `co_await` and `co_yield` now.

Associated spec clarification: https://github.com/KhronosGroup/OpenCL-Docs/pull/481


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D91348

Files:
  clang/lib/Sema/SemaExpr.cpp
  clang/test/SemaCXX/coroutines.cpp


Index: clang/test/SemaCXX/coroutines.cpp
===================================================================
--- clang/test/SemaCXX/coroutines.cpp
+++ clang/test/SemaCXX/coroutines.cpp
@@ -328,6 +328,7 @@
                         // expected-warning at -1 {{declaration does not declare anything}}
   sizeof(co_await a); // expected-error {{'co_await' cannot be used in an unevaluated context}}
                       // expected-error at -1 {{invalid application of 'sizeof' to an incomplete type 'void'}}
+                      // expected-warning at -2 {{expression with side effects has no effect in an unevaluated context}}
   typeid(co_await a); // expected-error {{'co_await' cannot be used in an unevaluated context}}
                       // expected-warning at -1 {{expression with side effects has no effect in an unevaluated context}}
                       // expected-warning at -2 {{expression result unused}}
@@ -335,6 +336,7 @@
                         // expected-warning at -1 {{declaration does not declare anything}}
   sizeof(co_yield 2); // expected-error {{'co_yield' cannot be used in an unevaluated context}}
                       // expected-error at -1 {{invalid application of 'sizeof' to an incomplete type 'void'}}
+                      // expected-warning at -2 {{expression with side effects has no effect in an unevaluated context}}
   typeid(co_yield 3); // expected-error {{'co_yield' cannot be used in an unevaluated context}}
                       // expected-warning at -1 {{expression with side effects has no effect in an unevaluated context}}
                       // expected-warning at -2 {{expression result unused}}
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -4027,7 +4027,7 @@
 
   bool IsUnevaluatedOperand =
       (ExprKind == UETT_SizeOf || ExprKind == UETT_AlignOf ||
-       ExprKind == UETT_PreferredAlignOf);
+       ExprKind == UETT_PreferredAlignOf || ExprKind == UETT_VecStep);
   if (IsUnevaluatedOperand) {
     ExprResult Result = CheckUnevaluatedOperand(E);
     if (Result.isInvalid())
@@ -4035,6 +4035,12 @@
     E = Result.get();
   }
 
+  // The operand for sizeof and alignof is in an unevaluated expression context,
+  // so side effects could result in unintended consequences.
+  if (IsUnevaluatedOperand && !inTemplateInstantiation() &&
+      E->HasSideEffects(Context, false))
+    Diag(E->getExprLoc(), diag::warn_side_effects_unevaluated_context);
+
   if (ExprKind == UETT_VecStep)
     return CheckVecStepTraitOperandType(*this, ExprTy, E->getExprLoc(),
                                         E->getSourceRange());
@@ -4071,12 +4077,6 @@
     return true;
   }
 
-  // The operand for sizeof and alignof is in an unevaluated expression context,
-  // so side effects could result in unintended consequences.
-  if (IsUnevaluatedOperand && !inTemplateInstantiation() &&
-      E->HasSideEffects(Context, false))
-    Diag(E->getExprLoc(), diag::warn_side_effects_unevaluated_context);
-
   if (CheckObjCTraitOperandConstraints(*this, ExprTy, E->getExprLoc(),
                                        E->getSourceRange(), ExprKind))
     return true;


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