Teach Wreturn-type, Wunreachable-code, and alpha.deadcode.UnreachableCode to treat __assume(0) like __builtin_unreachable.

Fixes PR29134.
https://reviews.llvm.org/D43221

llvm-svn: 325052

1 files changed, 12 insertions, 0 deletions

diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 7ddab9356b5..66f61708c5a 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -2917,6 +2917,18 @@ bool Expr::isConstantInitializer(ASTContext &Ctx, bool IsForRef,
   return false;
 }
 
+bool CallExpr::isBuiltinAssumeFalse(const ASTContext &Ctx) const {
+  const FunctionDecl* FD = getDirectCallee();
+  if (!FD || (FD->getBuiltinID() != Builtin::BI__assume &&
+              FD->getBuiltinID() != Builtin::BI__builtin_assume))
+    return false;
+  
+  const Expr* Arg = getArg(0);
+  bool ArgVal;
+  return !Arg->isValueDependent() &&
+         Arg->EvaluateAsBooleanCondition(ArgVal, Ctx) && !ArgVal;
+}
+
 namespace {
   /// \brief Look for any side effects within a Stmt.
   class SideEffectFinder : public ConstEvaluatedExprVisitor<SideEffectFinder> {