Index: include/llvm/IR/Function.h
===================================================================
--- include/llvm/IR/Function.h
+++ include/llvm/IR/Function.h
@@ -298,7 +298,8 @@
   /// @brief Determine if the function returns a structure through first
   /// pointer argument.
   bool hasStructRetAttr() const {
-    return AttributeSets.hasAttribute(1, Attribute::StructRet);
+    return AttributeSets.hasAttribute(1, Attribute::StructRet) ||
+           AttributeSets.hasAttribute(2, Attribute::StructRet);
   }
 
   /// @brief Determine if the parameter does not alias other parameters.
Index: lib/IR/Verifier.cpp
===================================================================
--- lib/IR/Verifier.cpp
+++ lib/IR/Verifier.cpp
@@ -853,7 +853,8 @@
     }
 
     if (Attrs.hasAttribute(Idx, Attribute::StructRet))
-      Assert1(Idx == 1, "Attribute sret is not on first parameter!", V);
+      Assert1(Idx == 1 || Idx == 2,
+              "Attribute sret is not on first or second parameter!", V);
 
     if (Attrs.hasAttribute(Idx, Attribute::InAlloca)) {
       Assert1(Idx == FT->getNumParams(),
Index: lib/Support/Atomic.cpp
===================================================================
--- lib/Support/Atomic.cpp
+++ lib/Support/Atomic.cpp
@@ -17,6 +17,7 @@
 using namespace llvm;
 
 #if defined(_MSC_VER)
+#include <Intrin.h>
 #include <windows.h>
 #undef MemoryFence
 #endif
Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -2302,7 +2302,12 @@
       Reg = MF.getRegInfo().createVirtualRegister(getRegClassFor(PtrTy));
       FuncInfo->setSRetReturnReg(Reg);
     }
-    SDValue Copy = DAG.getCopyToReg(DAG.getEntryNode(), dl, Reg, InVals[0]);
+    size_t I = 0, E = MF.getFunction()->arg_size();
+    AttributeSet Attrs = MF.getFunction()->getAttributes();
+    for (; I != E; ++I)
+      if (Attrs.hasAttribute(I + 1, Attribute::StructRet))
+        break;
+    SDValue Copy = DAG.getCopyToReg(DAG.getEntryNode(), dl, Reg, InVals[I]);
     Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Copy, Chain);
   }
 
Index: test/CodeGen/X86/win32_sret.ll
===================================================================
--- test/CodeGen/X86/win32_sret.ll
+++ test/CodeGen/X86/win32_sret.ll
@@ -181,3 +181,30 @@
   ret void
 }
 declare x86_thiscallcc void @test6_g(%struct.test6* sret, %struct.test6*)
+
+; Flipping the parameters at the IR level generates the same code.
+%struct.test7 = type { i32, i32, i32 }
+define void @test7_f(%struct.test7* %x) nounwind {
+; WIN32-LABEL: _test7_f:
+; MINGW_X86-LABEL: _test7_f:
+; CYGWIN-LABEL: _test7_f:
+; LINUX-LABEL: test7_f:
+
+; The %x argument is moved to %ecx on all OSs. It will be the this pointer.
+; WIN32:      movl    8(%ebp), %ecx
+; MINGW_X86:  movl    8(%ebp), %ecx
+; CYGWIN:     movl    8(%ebp), %ecx
+
+; The sret pointer is (%esp)
+; WIN32:          leal    8(%esp), %[[REG:e[a-d]x]]
+; WIN32-NEXT:     movl    %[[REG]], (%e{{([a-d]x)|(sp)}})
+; MINGW_X86:      leal    8(%esp), %[[REG:e[a-d]x]]
+; MINGW_X86-NEXT: movl    %[[REG]], (%e{{([a-d]x)|(sp)}})
+; CYGWIN:         leal    8(%esp), %[[REG:e[a-d]x]]
+; CYGWIN-NEXT:    movl    %[[REG]], (%e{{([a-d]x)|(sp)}})
+
+  %tmp = alloca %struct.test7, align 4
+  call x86_thiscallcc void @test7_g(%struct.test7* %x, %struct.test7* sret %tmp)
+  ret void
+}
+declare x86_thiscallcc void @test7_g(%struct.test7*, %struct.test7* sret)