X86: add test for realignment fix committed earlier.

Forgot "git add" for a new file.

llvm/test/CodeGen/X86/swifttail-realign.ll

@@ -0,0 +1,29 @@
+; RUN: llc -mtriple=x86_64-linux-gnu %s -o - | FileCheck %s
+
+declare swifttailcc void @callee([6 x i64], i64, i64)
+
+@var = external global i8*
+
+define swifttailcc void @caller(i64 %n) {
+; CHECK-LABEL: caller:
+; CHECK: subq $16, %rsp
+; CHECK: pushq %rbp
+; CHECK: movq %rsp, %rbp
+; CHECK: pushq %rbx
+; CHECK: andq $-32, %rsp
+; [... don't really care what happens to rsp to allocate %ptr ...]
+; CHECK: movq 24(%rbp), [[RETADDR:%.*]]
+; CHECK: movq [[RETADDR]], 8(%rbp)
+; CHECK: movq $42, 16(%rbp)
+; CHECK: movq $0, 24(%rbp)
+; CHECK: leaq -8(%rbp), %rsp
+; CHECK: popq %rbx
+; CHECK: popq %rbp
+; CHECK: jmp callee
+
+  call void asm sideeffect "", "~{rbx}"()
+  %ptr = alloca i8, i64 %n, align 32
+  store i8* %ptr, i8** @var
+  tail call swifttailcc void @callee([6 x i64] undef, i64 42, i64 0)
+  ret void
+}