From 8e36a5c960e07555d80fb98d71c692c20f3ea6c4 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Mon, 29 Mar 2010 21:27:30 +0000
Subject: [PATCH] Fix PR4975. Avoid referencing empty vector.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99840 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../SelectionDAG/SelectionDAGBuilder.cpp        |  6 ++++--
 test/CodeGen/Generic/2010-ZeroSizedArg.ll       | 17 +++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)
 create mode 100644 test/CodeGen/Generic/2010-ZeroSizedArg.ll

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index faefe2932ec..7a0daf69c84 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -6051,8 +6051,10 @@ void SelectionDAGISel::LowerArguments(BasicBlock *LLVMBB) {
     }
 
     if (!I->use_empty()) {
-      SDValue Res = DAG.getMergeValues(&ArgValues[0], NumValues,
-                                       SDB->getCurDebugLoc());
+      SDValue Res;
+      if (!ArgValues.empty())
+        Res = DAG.getMergeValues(&ArgValues[0], NumValues,
+                                 SDB->getCurDebugLoc());
       SDB->setValue(I, Res);
 
       // If this argument is live outside of the entry block, insert a copy from
diff --git a/test/CodeGen/Generic/2010-ZeroSizedArg.ll b/test/CodeGen/Generic/2010-ZeroSizedArg.ll
new file mode 100644
index 00000000000..ba40bd08e8e
--- /dev/null
+++ b/test/CodeGen/Generic/2010-ZeroSizedArg.ll
@@ -0,0 +1,17 @@
+; RUN: llc < %s
+; PR4975
+
+%0 = type <{ [0 x i32] }>
+%union.T0 = type { }
+
+@.str = private constant [1 x i8] c" "
+
+define arm_apcscc void @t(%0) nounwind {
+entry:
+  %arg0 = alloca %union.T0
+  %1 = bitcast %union.T0* %arg0 to %0*
+  store %0 %0, %0* %1, align 1
+  ret void
+}
+
+declare arm_apcscc i32 @printf(i8*, ...)
-- 
2.34.1