Index: llvm/trunk/lib/IR/Value.cpp
===================================================================
--- llvm/trunk/lib/IR/Value.cpp
+++ llvm/trunk/lib/IR/Value.cpp
@@ -627,9 +627,10 @@
   CanBeNull = false;
   if (const Argument *A = dyn_cast<Argument>(this)) {
     DerefBytes = A->getDereferenceableBytes();
-    if (DerefBytes == 0 && A->hasByValAttr()) {
+    if (DerefBytes == 0 && (A->hasByValAttr() || A->hasStructRetAttr())) {
       Type *PT = cast<PointerType>(A->getType())->getElementType();
-      DerefBytes = DL.getTypeStoreSize(PT);
+      if (PT->isSized())
+        DerefBytes = DL.getTypeStoreSize(PT);
     }
     if (DerefBytes == 0) {
       DerefBytes = A->getDereferenceableOrNullBytes();
Index: llvm/trunk/test/Analysis/ValueTracking/memory-dereferenceable.ll
===================================================================
--- llvm/trunk/test/Analysis/ValueTracking/memory-dereferenceable.ll
+++ llvm/trunk/test/Analysis/ValueTracking/memory-dereferenceable.ll
@@ -20,7 +20,8 @@
 @globalptr.align16 = external global i8, align 16
 
 ; CHECK-LABEL: 'test'
-define void @test(i32 addrspace(1)* dereferenceable(8) %dparam,
+define void @test(%struct.A* sret %result,
+                  i32 addrspace(1)* dereferenceable(8) %dparam,
                   i8 addrspace(1)* dereferenceable(32) align 1 %dparam.align1,
                   i8 addrspace(1)* dereferenceable(32) align 16 %dparam.align16,
                   i8* byval %i8_byval,
@@ -53,6 +54,15 @@
     %baa_cast = bitcast i8* %big_array_alloca to i32*
     %baa_load = load i32, i32* %baa_cast
 
+    ; Loads from sret arguments
+; CHECK: %sret_gep{{.*}}(aligned)
+    %sret_gep = getelementptr inbounds %struct.A, %struct.A* %result, i64 0, i32 1, i64 2
+    load i8, i8* %sret_gep
+
+; CHECK-NOT: %sret_gep_outside
+    %sret_gep_outside = getelementptr %struct.A, %struct.A* %result, i64 0, i32 1, i64 7
+    load i8, i8* %sret_gep_outside
+
 ; CHECK: %dparam{{.*}}(aligned)
     %load3 = load i32, i32 addrspace(1)* %dparam