diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -4257,16 +4257,19 @@
       isTailCall = false;
   }
 
-  if (isTailCall && !IsMustTail) {
+  if (isTailCall) {
+    // It seems this function actually checks for sib call.
     // Check if it's really possible to do a tail call.
-    isTailCall = IsEligibleForTailCallOptimization(
+    IsSibcall = IsEligibleForTailCallOptimization(
         Callee, CallConv, IsCalleePopSRet, isVarArg, CLI.RetTy, Outs, OutVals,
         Ins, DAG);
 
-    // Sibcalls are automatically detected tailcalls which do not require
-    // ABI changes.
-    if (!IsGuaranteeTCO && isTailCall)
-      IsSibcall = true;
+    if (!IsMustTail) {
+      isTailCall = IsSibcall;
+      // Sibcalls are automatically detected tailcalls which do not require ABI
+      // changes.
+      IsSibcall = IsSibcall && !IsGuaranteeTCO;
+    }
 
     if (isTailCall)
       ++NumTailCalls;
@@ -4305,7 +4308,8 @@
     NumBytes = GetAlignedArgumentStackSize(NumBytes, DAG);
 
   int FPDiff = 0;
-  if (isTailCall &&
+  // Sibcall should not adjust stack pointer.
+  if (isTailCall && !IsSibcall &&
       shouldGuaranteeTCO(CallConv,
                          MF.getTarget().Options.GuaranteedTailCallOpt)) {
     // Lower arguments at fp - stackoffset + fpdiff.
diff --git a/llvm/test/CodeGen/X86/musttail-struct.ll b/llvm/test/CodeGen/X86/musttail-struct.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/X86/musttail-struct.ll
@@ -0,0 +1,57 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s
+; RUN: llc < %s -mtriple=i686-unknown-unknown | FileCheck %s
+
+; Test correct handling of musttail call with struct.
+
+%struct.1xi32 = type { [1 x i32] }
+%struct.3xi32 = type { [3 x i32] }
+%struct.5xi32 = type { [5 x i32] }
+
+declare dso_local i32 @Func1(ptr byval(%struct.1xi32) %0)
+declare dso_local i32 @Func3(ptr byval(%struct.3xi32) %0)
+declare dso_local i32 @Func5(ptr byval(%struct.5xi32) %0)
+declare dso_local i32 @FuncManyArgs(i32 %0, i32 %1, i32 %2, i32 %3, i32 %4, i32 %5, i8 %6, ptr byval(%struct.5xi32) %7)
+
+define dso_local i32 @test1(ptr byval(%struct.1xi32) %0) {
+; CHECK-LABEL: test1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    jmp Func1 # TAILCALL
+  %r = musttail call i32 @Func1(ptr byval(%struct.1xi32) %0)
+  ret i32 %r
+}
+
+define dso_local i32 @test3(ptr byval(%struct.3xi32) %0) {
+; CHECK-LABEL: test3:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    jmp Func3 # TAILCALL
+  %r = musttail call i32 @Func3(ptr byval(%struct.3xi32) %0)
+  ret i32 %r
+}
+
+; sizeof(%struct.5xi32) > 16, in x64 this is passed on stack.
+define dso_local i32 @test5(ptr byval(%struct.5xi32) %0) {
+; CHECK-LABEL: test5:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    jmp Func5 # TAILCALL
+  %r = musttail call i32 @Func5(ptr byval(%struct.5xi32) %0)
+  ret i32 %r
+}
+
+; Test passing multiple arguments with different sizes on stack. In x64 Linux
+; the first 6 are passed by register.
+define dso_local i32 @testManyArgs(i32 %0, i32 %1, i32 %2, i32 %3, i32 %4, i32 %5, i8 %6, ptr byval(%struct.5xi32) %7) {
+; CHECK-LABEL: testManyArgs:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    jmp FuncManyArgs # TAILCALL
+  %r = musttail call i32 @FuncManyArgs(i32 %0, i32 %1, i32 %2, i32 %3, i32 %4, i32 %5, i8 %6, ptr byval(%struct.5xi32) %7)
+  ret i32 %r
+}
+
+define dso_local i32 @testRecursion(i32 %0, i32 %1, i32 %2, i32 %3, i32 %4, i32 %5, i8 %6, ptr byval(%struct.5xi32) %7) {
+; CHECK-LABEL: testRecursion:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    jmp testRecursion # TAILCALL
+  %r = musttail call i32 @testRecursion(i32 %0, i32 %1, i32 %2, i32 %3, i32 %4, i32 %5, i8 %6, ptr byval(%struct.5xi32) %7)
+  ret i32 %r
+}
diff --git a/llvm/test/CodeGen/X86/musttail-tailcc.ll b/llvm/test/CodeGen/X86/musttail-tailcc.ll
--- a/llvm/test/CodeGen/X86/musttail-tailcc.ll
+++ b/llvm/test/CodeGen/X86/musttail-tailcc.ll
@@ -54,15 +54,6 @@
 ;
 ; X32-LABEL: void_test:
 ; X32:       # %bb.0: # %entry
-; X32-NEXT:    pushl %esi
-; X32-NEXT:    .cfi_def_cfa_offset 8
-; X32-NEXT:    .cfi_offset %esi, -8
-; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X32-NEXT:    movl {{[0-9]+}}(%esp), %esi
-; X32-NEXT:    movl %esi, {{[0-9]+}}(%esp)
-; X32-NEXT:    movl %eax, {{[0-9]+}}(%esp)
-; X32-NEXT:    popl %esi
-; X32-NEXT:    .cfi_def_cfa_offset 4
 ; X32-NEXT:    jmp void_test # TAILCALL
   entry:
    musttail call tailcc void @void_test( i32 %0, i32 %1, i32 %2, i32 %3)
@@ -76,15 +67,6 @@
 ;
 ; X32-LABEL: i1test:
 ; X32:       # %bb.0: # %entry
-; X32-NEXT:    pushl %esi
-; X32-NEXT:    .cfi_def_cfa_offset 8
-; X32-NEXT:    .cfi_offset %esi, -8
-; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X32-NEXT:    movl {{[0-9]+}}(%esp), %esi
-; X32-NEXT:    movl %esi, {{[0-9]+}}(%esp)
-; X32-NEXT:    movl %eax, {{[0-9]+}}(%esp)
-; X32-NEXT:    popl %esi
-; X32-NEXT:    .cfi_def_cfa_offset 4
 ; X32-NEXT:    jmp i1test # TAILCALL
   entry:
   %4 = musttail call tailcc i1 @i1test( i32 %0, i32 %1, i32 %2, i32 %3)