diff --git a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
index 81dbd329c4b6..d372ba22d6e3 100644
--- a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -531,6 +531,13 @@ DAE::Liveness DAE::SurveyUses(const Value *V, UseVector &MaybeLiveUses) {
 // well as arguments to functions which have their "address taken".
 //
 void DAE::SurveyFunction(const Function &F) {
+  // Functions with inalloca parameters are expecting args in a particular
+  // register and memory layout.
+  if (F.getAttributes().hasAttrSomewhere(Attribute::InAlloca)) {
+    MarkLive(F);
+    return;
+  }
+
   unsigned RetCount = NumRetVals(&F);
   // Assume all return values are dead
   typedef SmallVector<Liveness, 5> RetVals;
diff --git a/llvm/test/Transforms/DeadArgElim/keepalive.ll b/llvm/test/Transforms/DeadArgElim/keepalive.ll
index 82e01f225843..b66df792ca84 100644
--- a/llvm/test/Transforms/DeadArgElim/keepalive.ll
+++ b/llvm/test/Transforms/DeadArgElim/keepalive.ll
@@ -28,4 +28,20 @@ define void @caller() {
         ret void
 }
 
+; We can't remove 'this' here, as that would put argmem in ecx instead of
+; memory.
+define internal x86_thiscallcc i32 @unused_this(i32* %this, i32* inalloca %argmem) {
+	%v = load i32* %argmem
+	ret i32 %v
+}
+; CHECK-LABEL: define internal x86_thiscallcc i32 @unused_this(i32* %this, i32* inalloca %argmem)
+
+define i32 @caller2() {
+	%t = alloca i32
+	%m = alloca i32, inalloca
+	store i32 42, i32* %m
+	%v = call x86_thiscallcc i32 @unused_this(i32* %t, i32* inalloca %m)
+	ret i32 %v
+}
+
 ; CHECK: attributes #0 = { nounwind }