Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -4157,9 +4157,9 @@
   if (RegInfo->needsStackRealignment(MF))
     return false;
 
-  // Also avoid sibcall optimization if either caller or callee uses struct
-  // return semantics.
-  if (isCalleeStructRet || isCallerStructRet)
+  // 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
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
 ;
 ; X32ABI-LABEL: t15:
 ; X32ABI:       # %bb.0:
-; X32ABI-NEXT:    pushq %rbx
-; X32ABI-NEXT:    movl %edi, %ebx
-; X32ABI-NEXT:    callq f
-; X32ABI-NEXT:    movl %ebx, %eax
-; X32ABI-NEXT:    popq %rbx
-; X32ABI-NEXT:    retq
+; X32ABI-NEXT:    jmp f # TAILCALL
   tail call fastcc void @f(%struct.foo* noalias sret %agg.result) nounwind
   ret void
 }
@@ -606,3 +596,86 @@
 }
 
 declare fastcc double @foo20(double) nounwind
+
+; bug 28417
+define fastcc void @t21_sret_to_sret(%struct.foo* noalias sret %agg.result) nounwind  {
+; 32-LABEL: t21_sret_to_sret:
+; 32: jmp {{_?}}t21_f_sret
+; 64-LABEL: t21_sret_to_sret:
+; 64: jmp {{_?}}t21_f_sret
+; X32-LABEL: t21_sret_to_sret:
+; X32:       # %bb.0:
+; X32-NEXT:    jmp t21_f_sret # TAILCALL
+;
+; X64-LABEL: t21_sret_to_sret:
+; X64:       # %bb.0:
+; X64-NEXT:    jmp t21_f_sret # TAILCALL
+;
+; X32ABI-LABEL: t21_sret_to_sret:
+; X32ABI:       # %bb.0:
+; X32ABI-NEXT:    jmp t21_f_sret # TAILCALL
+  tail call fastcc void @t21_f_sret(%struct.foo* noalias sret %agg.result) nounwind
+  ret void
+}
+
+define fastcc void @t21_sret_to_non_sret(%struct.foo* noalias sret %agg.result) nounwind  {
+; 32-LABEL: t21_sret_to_non_sret:
+; 32: calll {{_?}}t21_f_non_sret
+; 32: retl
+; 64-LABEL: t21_sret_to_non_sret:
+; 64: callq {{_?}}t21_f_non_sret
+; 64: retq
+; X32-LABEL: t21_sret_to_non_sret:
+; X32:       # %bb.0:
+; X32-NEXT:    pushl %esi
+; X32-NEXT:    subl $8, %esp
+; X32-NEXT:    movl %ecx, %esi
+; X32-NEXT:    calll t21_f_non_sret
+; X32-NEXT:    movl %esi, %eax
+; X32-NEXT:    addl $8, %esp
+; X32-NEXT:    popl %esi
+; X32-NEXT:    retl
+;
+; X64-LABEL: t21_sret_to_non_sret:
+; X64:       # %bb.0:
+; X64-NEXT:    pushq %rbx
+; X64-NEXT:    movq %rdi, %rbx
+; X64-NEXT:    callq t21_f_non_sret
+; X64-NEXT:    movq %rbx, %rax
+; X64-NEXT:    popq %rbx
+; X64-NEXT:    retq
+;
+; X32ABI-LABEL: t21_sret_to_non_sret:
+; X32ABI:       # %bb.0:
+; X32ABI-NEXT:    pushq %rbx
+; X32ABI-NEXT:    movl %edi, %ebx
+; X32ABI-NEXT:    callq t21_f_non_sret
+; X32ABI-NEXT:    movl %ebx, %eax
+; X32ABI-NEXT:    popq %rbx
+; X32ABI-NEXT:    retq
+  tail call fastcc void @t21_f_non_sret(%struct.foo* %agg.result) nounwind
+  ret void
+}
+
+define fastcc void @t21_non_sret_to_sret(%struct.foo* %agg.result) nounwind  {
+; 32-LABEL: t21_non_sret_to_sret:
+; 32: jmp {{_?}}t21_f_sret
+; 64-LABEL: t21_non_sret_to_sret:
+; 64: jmp {{_?}}t21_f_sret
+; X32-LABEL: t21_non_sret_to_sret:
+; X32:       # %bb.0:
+; X32-NEXT:    jmp t21_f_sret # TAILCALL
+;
+; X64-LABEL: t21_non_sret_to_sret:
+; X64:       # %bb.0:
+; X64-NEXT:    jmp t21_f_sret # TAILCALL
+;
+; X32ABI-LABEL: t21_non_sret_to_sret:
+; X32ABI:       # %bb.0:
+; X32ABI-NEXT:    jmp t21_f_sret # TAILCALL
+  tail call fastcc void @t21_f_sret(%struct.foo* noalias sret %agg.result) nounwind
+  ret void
+}
+
+declare fastcc void @t21_f_sret(%struct.foo* noalias sret) nounwind
+declare fastcc void @t21_f_non_sret(%struct.foo*) nounwind