[X86] Add test where storing return addr clobbers argument stack slot.

Currently for the test the return address is written to the stack before
loading the argument from an aliasing stack slot.

Author: fhahn

llvm/test/CodeGen/X86/swifttailcc-store-ret-address-aliasing-stack-slot.ll

@@ -0,0 +1,44 @@
+; RUN: llc %s -o - | FileCheck %s
+
+target triple = "x86_64-apple-macosx"
+
+declare swifttailcc void @tc_fn(ptr swiftasync, i64, ptr, i8, ptr swiftself)
+
+declare void @foo()
+
+; FIXME: Currently the return address is written to the stack before loading the
+; argument from an aliasing stack slot.
+define swifttailcc void @test(ptr %0, ptr swiftasync %1, i64 %2, i64 %3, ptr %4, ptr %5, i64 %6, ptr %7, i8 %8) {
+; CHECK-LABEL: test:
+; CHECK:       ## %bb.0: ## %entry
+; CHECK-NEXT:    pushq %r15
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    pushq %rbx
+; CHECK-NEXT:    .cfi_def_cfa_offset 24
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    .cfi_def_cfa_offset 32
+; CHECK-NEXT:    .cfi_offset %rbx, -24
+; CHECK-NEXT:    .cfi_offset %r15, -16
+; CHECK-NEXT:    movq %r9, %r13
+; CHECK-NEXT:    movq %r8, %rbx
+; CHECK-NEXT:    movq {{[0-9]+}}(%rsp), %r15
+; CHECK-NEXT:    callq _foo
+; CHECK-NEXT:    movq %r14, (%rax)
+; CHECK-NEXT:    movq {{[0-9]+}}(%rsp), %rcx
+; CHECK-NEXT:    movq %rcx, [[OFF:[0-9]+]](%rsp)
+; CHECK-NEXT:    movl [[OFF]](%rsp), %edx
+; CHECK-NEXT:    movq %rax, %r14
+; CHECK-NEXT:    movq %r13, %rdi
+; CHECK-NEXT:    movq %r15, %rsi
+; CHECK-NEXT:    movq %rbx, %r13
+; CHECK-NEXT:    addq $8, %rsp
+; CHECK-NEXT:    popq %rbx
+; CHECK-NEXT:    popq %r15
+; CHECK-NEXT:    addq $16, %rsp
+; CHECK-NEXT:    jmp _tc_fn ## TAILCALL
+entry:
+  %res = tail call ptr @foo()
+  store ptr %1, ptr %res, align 8
+  musttail call swifttailcc void @tc_fn(ptr swiftasync %res, i64 %6, ptr %7, i8 %8, ptr swiftself %5)
+  ret void
+}