Handle __assume in the VoidExprEvaluator

This is a follow-up to an IRC conversation with Richard last night; __assume
does not evaluate its argument, and so the argument should not contribute to
whether (__assume(e), constant) can be used where a constant is required.

llvm-svn: 213267

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 3552d65..b1d2265 100644 (file)
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -7955,6 +7955,16 @@ public:
       return true;
     }
   }
+
+  bool VisitCallExpr(const CallExpr *E) {
+    switch (E->getBuiltinCallee()) {
+    default:
+      return ExprEvaluatorBaseTy::VisitCallExpr(E);
+    case Builtin::BI__assume:
+      // The argument is not evaluated!
+      return true;
+    }
+  }
 };
 } // end anonymous namespace
 

diff --git a/clang/test/Sema/builtin-assume.c b/clang/test/Sema/builtin-assume.c
index 6c83b69..1f6a3a0 100644 (file)
--- a/clang/test/Sema/builtin-assume.c
+++ b/clang/test/Sema/builtin-assume.c
@@ -3,6 +3,9 @@
 int foo(int *a, int i) {
   __assume(i != 4);
   __assume(++i > 2); //expected-warning {{the argument to __assume has side effects that will be discarded}}
+
+  int test = sizeof(struct{char qq[(__assume(i != 5), 7)];});
+
   return a[i];
 }