Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -4182,10 +4182,10 @@
   if (RegInfo->needsStackRealignment(MF))
     return false;
 
-  // Also avoid sibcall optimization if either caller or callee uses struct
-  // return semantics.
-  if (isCalleeStructRet || isCallerStructRet)
-    return false;
+  // Struct-return functions need to return its argument in RAX, so they can not
+  // sibcall non-struct-return functions.
+  if (!isCalleeStructRet && isCallerStructRet)
+   return false;
 
   // Do not sibcall optimize vararg calls unless all arguments are passed via
   // registers.
Index: test/CodeGen/X86/sibcall.ll
===================================================================
--- test/CodeGen/X86/sibcall.ll
+++ test/CodeGen/X86/sibcall.ll
@@ -448,21 +448,11 @@
 ;
 ; X64-LABEL: t15:
 ; X64:       # %bb.0:
-; X64-NEXT:    pushq %rbx
-; X64-NEXT:    movq %rdi, %rbx
-; X64-NEXT:    callq f
-; X64-NEXT:    movq %rbx, %rax
-; X64-NEXT:    popq %rbx
-; X64-NEXT:    retq
+; X64-NEXT:    jmp f # TAILCALL
 ;
 ; X32-LABEL: t15:
 ; X32:       # %bb.0:
-; X32-NEXT:    pushq %rbx
-; X32-NEXT:    movl %edi, %ebx
-; X32-NEXT:    callq f
-; X32-NEXT:    movl %ebx, %eax
-; X32-NEXT:    popq %rbx
-; X32-NEXT:    retq
+; X32-NEXT:    jmp f # TAILCALL
   tail call fastcc void @f(%struct.foo* noalias sret %agg.result) nounwind
   ret void
 }
@@ -611,32 +601,15 @@
 define fastcc void @t21_sret_to_sret(%struct.foo* noalias sret %agg.result) nounwind  {
 ; X86-LABEL: t21_sret_to_sret:
 ; X86:       # %bb.0:
-; X86-NEXT:    pushl %esi
-; X86-NEXT:    subl $8, %esp
-; X86-NEXT:    movl %ecx, %esi
-; X86-NEXT:    calll t21_f_sret
-; X86-NEXT:    movl %esi, %eax
-; X86-NEXT:    addl $8, %esp
-; X86-NEXT:    popl %esi
-; X86-NEXT:    retl
+; X86-NEXT:    jmp t21_f_sret # TAILCALL
 ;
 ; X64-LABEL: t21_sret_to_sret:
 ; X64:       # %bb.0:
-; X64-NEXT:    pushq %rbx
-; X64-NEXT:    movq %rdi, %rbx
-; X64-NEXT:    callq t21_f_sret
-; X64-NEXT:    movq %rbx, %rax
-; X64-NEXT:    popq %rbx
-; X64-NEXT:    retq
+; X64-NEXT:    jmp t21_f_sret # TAILCALL
 ;
 ; X32-LABEL: t21_sret_to_sret:
 ; X32:       # %bb.0:
-; X32-NEXT:    pushq %rbx
-; X32-NEXT:    movl %edi, %ebx
-; X32-NEXT:    callq t21_f_sret
-; X32-NEXT:    movl %ebx, %eax
-; X32-NEXT:    popq %rbx
-; X32-NEXT:    retq
+; X32-NEXT:    jmp t21_f_sret # TAILCALL
   tail call fastcc void @t21_f_sret(%struct.foo* noalias sret %agg.result) nounwind
   ret void
 }
@@ -677,24 +650,15 @@
 define fastcc void @t21_non_sret_to_sret(%struct.foo* %agg.result) nounwind  {
 ; X86-LABEL: t21_non_sret_to_sret:
 ; X86:       # %bb.0:
-; X86-NEXT:    subl $12, %esp
-; X86-NEXT:    calll t21_f_sret
-; X86-NEXT:    addl $12, %esp
-; X86-NEXT:    retl
+; X86-NEXT:    jmp t21_f_sret # TAILCALL
 ;
 ; X64-LABEL: t21_non_sret_to_sret:
 ; X64:       # %bb.0:
-; X64-NEXT:    pushq %rax
-; X64-NEXT:    callq t21_f_sret
-; X64-NEXT:    popq %rax
-; X64-NEXT:    retq
+; X64-NEXT:    jmp t21_f_sret # TAILCALL
 ;
 ; X32-LABEL: t21_non_sret_to_sret:
 ; X32:       # %bb.0:
-; X32-NEXT:    pushq %rax
-; X32-NEXT:    callq t21_f_sret
-; X32-NEXT:    popq %rax
-; X32-NEXT:    retq
+; X32-NEXT:    jmp t21_f_sret # TAILCALL
   tail call fastcc void @t21_f_sret(%struct.foo* noalias sret %agg.result) nounwind
   ret void
 }
@@ -705,26 +669,15 @@
 define ccc void @t22_non_sret_to_sret(%struct.foo* %agg.result) nounwind  {
 ; X86-LABEL: t22_non_sret_to_sret:
 ; X86:       # %bb.0:
-; X86-NEXT:    subl $12, %esp
-; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X86-NEXT:    movl %eax, (%esp)
-; X86-NEXT:    calll t22_f_sret
-; X86-NEXT:    addl $8, %esp
-; X86-NEXT:    retl
+; X86-NEXT:    jmp t22_f_sret # TAILCALL
 ;
 ; X64-LABEL: t22_non_sret_to_sret:
 ; X64:       # %bb.0:
-; X64-NEXT:    pushq %rax
-; X64-NEXT:    callq t22_f_sret
-; X64-NEXT:    popq %rax
-; X64-NEXT:    retq
+; X64-NEXT:    jmp t22_f_sret # TAILCALL
 ;
 ; X32-LABEL: t22_non_sret_to_sret:
 ; X32:       # %bb.0:
-; X32-NEXT:    pushq %rax
-; X32-NEXT:    callq t22_f_sret
-; X32-NEXT:    popq %rax
-; X32-NEXT:    retq
+; X32-NEXT:    jmp t22_f_sret # TAILCALL
   tail call ccc void @t22_f_sret(%struct.foo* noalias sret %agg.result) nounwind
   ret void
 }