From 892bb0cace9f733df800e4875fcf9325f860501a Mon Sep 17 00:00:00 2001
From: Reid Kleckner <reid@kleckner.net>
Date: Wed, 20 May 2015 21:59:25 +0000
Subject: Evaluate union cast subexpressions when the cast value is unused

Fixes PR23597.

llvm-svn: 237839
---
 clang/lib/CodeGen/CGExprAgg.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

(limited to 'clang/lib/CodeGen/CGExprAgg.cpp')

diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index 77e4464ee8c..6fedf0efda9 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -584,7 +584,12 @@ void AggExprEmitter::VisitCastExpr(CastExpr *E) {
   }
       
   case CK_ToUnion: {
-    if (Dest.isIgnored()) break;
+    // Evaluate even if the destination is ignored.
+    if (Dest.isIgnored()) {
+      CGF.EmitAnyExpr(E->getSubExpr(), AggValueSlot::ignored(),
+                      /*ignoreResult=*/true);
+      break;
+    }
 
     // GCC union extension
     QualType Ty = E->getSubExpr()->getType();
-- 
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