If the first argument of __builtin_object_size can be folded to a constant
pointer, but such folding encounters side-effects, ignore the side-effects
rather than performing them at runtime: CodeGen generates wrong code for
__builtin_object_size in that case.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@157310 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 5362320..d3ab84f 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -4319,10 +4319,16 @@
}
bool IntExprEvaluator::TryEvaluateBuiltinObjectSize(const CallExpr *E) {
- // TODO: Perhaps we should let LLVM lower this?
LValue Base;
- if (!EvaluatePointer(E->getArg(0), Base, Info))
- return false;
+
+ {
+ // The operand of __builtin_object_size is never evaluated for side-effects.
+ // If there are any, but we can determine the pointed-to object anyway, then
+ // ignore the side-effects.
+ SpeculativeEvaluationRAII SpeculativeEval(Info);
+ if (!EvaluatePointer(E->getArg(0), Base, Info))
+ return false;
+ }
// If we can prove the base is null, lower to zero now.
if (!Base.getLValueBase()) return Success(0, E);
@@ -4355,13 +4361,16 @@
return true;
// If evaluating the argument has side-effects we can't determine
- // the size of the object and lower it to unknown now.
+ // the size of the object and lower it to unknown now. CodeGen relies on
+ // us to handle all cases where the expression has side-effects.
if (E->getArg(0)->HasSideEffects(Info.Ctx)) {
if (E->getArg(1)->EvaluateKnownConstInt(Info.Ctx).getZExtValue() <= 1)
return Success(-1ULL, E);
return Success(0, E);
}
+ // Expression had no side effects, but we couldn't statically determine the
+ // size of the referenced object.
return Error(E);
}