Enhance dead store checker to not flag preincrements to dead variables where the preincrement is a subexpression, e.g. foo(++x); This can cause false negatives, but will remove a whole class of false positives.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@57554 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/CheckDeadStores.cpp b/lib/Analysis/CheckDeadStores.cpp
index d87bfb1..2afc7e0 100644
--- a/lib/Analysis/CheckDeadStores.cpp
+++ b/lib/Analysis/CheckDeadStores.cpp
@@ -149,6 +149,13 @@
else if (UnaryOperator* U = dyn_cast<UnaryOperator>(S)) {
if (!U->isIncrementOp())
return;
+
+ // Handle: ++x within a subexpression. The solution is not warn
+ // about preincrements to dead variables when the preincrement occurs
+ // as a subexpression. This can lead to false negatives, e.g. "(++x);"
+ // A generalized dead code checker should find such issues.
+ if (U->isPrefix() && Parents.isSubExpr(U))
+ return;
Expr *Ex = U->getSubExpr()->IgnoreParenCasts();