Track in the AST whether the operand to a UnaryOperator can overflow and then use that logic when evaluating constant expressions and emitting codegen.

llvm-svn: 322074

1 files changed, 17 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index a6f3ee2c094..1d7a5d2e128 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -12178,6 +12178,16 @@ ExprResult Sema::BuildBinOp(Scope *S, SourceLocation OpLoc,
   return CreateBuiltinBinOp(OpLoc, Opc, LHSExpr, RHSExpr);
 }
 
+static bool isOverflowingIntegerType(ASTContext &Ctx, QualType T) {
+  if (T.isNull() || T->isDependentType())
+    return false;
+
+  if (!T->isPromotableIntegerType())
+    return true;
+
+  return Ctx.getIntWidth(T) >= Ctx.getIntWidth(Ctx.IntTy);
+}
+
 ExprResult Sema::CreateBuiltinUnaryOp(SourceLocation OpLoc,
                                       UnaryOperatorKind Opc,
                                       Expr *InputExpr) {
@@ -12185,6 +12195,8 @@ ExprResult Sema::CreateBuiltinUnaryOp(SourceLocation OpLoc,
   ExprValueKind VK = VK_RValue;
   ExprObjectKind OK = OK_Ordinary;
   QualType resultType;
+  bool CanOverflow = false;
+
   bool ConvertHalfVec = false;
   if (getLangOpts().OpenCL) {
     QualType Ty = InputExpr->getType();
@@ -12210,6 +12222,7 @@ ExprResult Sema::CreateBuiltinUnaryOp(SourceLocation OpLoc,
                                                 Opc == UO_PostInc,
                                                 Opc == UO_PreInc ||
                                                 Opc == UO_PreDec);
+    CanOverflow = isOverflowingIntegerType(Context, resultType);
     break;
   case UO_AddrOf:
     resultType = CheckAddressOfOperand(Input, OpLoc);
@@ -12223,6 +12236,8 @@ ExprResult Sema::CreateBuiltinUnaryOp(SourceLocation OpLoc,
   }
   case UO_Plus:
   case UO_Minus:
+    CanOverflow = Opc == UO_Minus &&
+                  isOverflowingIntegerType(Context, Input.get()->getType());
     Input = UsualUnaryConversions(Input.get());
     if (Input.isInvalid()) return ExprError();
     // Unary plus and minus require promoting an operand of half vector to a
@@ -12259,6 +12274,7 @@ ExprResult Sema::CreateBuiltinUnaryOp(SourceLocation OpLoc,
     if (Input.isInvalid())
       return ExprError();
     resultType = Input.get()->getType();
+
     if (resultType->isDependentType())
       break;
     // C99 6.5.3.3p1. We allow complex int and float as a GCC extension.
@@ -12373,7 +12389,7 @@ ExprResult Sema::CreateBuiltinUnaryOp(SourceLocation OpLoc,
     CheckArrayAccess(Input.get());
 
   auto *UO = new (Context)
-      UnaryOperator(Input.get(), Opc, resultType, VK, OK, OpLoc);
+      UnaryOperator(Input.get(), Opc, resultType, VK, OK, OpLoc, CanOverflow);
   // Convert the result back to a half vector.
   if (ConvertHalfVec)
     return convertVector(UO, Context.HalfTy, *this);