1; RUN: llc -relocation-model=static -verify-machineinstrs -O2 < %s | FileCheck %s 2; RUN: llc -relocation-model=static -verify-machineinstrs -global-isel -O2 < %s | FileCheck %s 3 4; The call to function TestBar should be a tail call, when in C++ the string 5; `ret` is RVO returned. 6; string TestFoo() { 7; string ret = undef; 8; TestBar(&ret); // tail call optimized 9; return ret; 10; } 11 12target triple = "aarch64-linux-gnu" 13 14%class.basic_string.11.42.73 = type { %"class.__gnu_cxx::__versa_string.10.41.72" } 15%"class.__gnu_cxx::__versa_string.10.41.72" = type { %"class.__gnu_cxx::__sso_string_base.9.40.71" } 16%"class.__gnu_cxx::__sso_string_base.9.40.71" = type { %"struct.__gnu_cxx::__vstring_utility<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider.7.38.69", i64, %union.anon.8.39.70 } 17%"struct.__gnu_cxx::__vstring_utility<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider.7.38.69" = type { ptr } 18%union.anon.8.39.70 = type { i64, [8 x i8] } 19 20declare void @TestBaz(ptr noalias sret(%class.basic_string.11.42.73) %arg) 21 22define void @TestBar(ptr noalias sret(%class.basic_string.11.42.73) %arg) { 23bb: 24 call void @TestBaz(ptr noalias sret(%class.basic_string.11.42.73) %arg) 25 ret void 26} 27 28define void @TestFoo(ptr noalias sret(%class.basic_string.11.42.73) %arg) { 29; CHECK-LABEL: TestFoo: 30; CHECK: b TestBar 31bb: 32 %tmp = getelementptr inbounds %class.basic_string.11.42.73, ptr %arg, i64 0, i32 0, i32 0, i32 2 33 store ptr %tmp, ptr %arg, align 8 34 tail call void @llvm.memcpy.p0.p0.i64(ptr %tmp, ptr nonnull undef, i64 13, i1 false) 35 %tmp3 = getelementptr inbounds %class.basic_string.11.42.73, ptr %arg, i64 0, i32 0, i32 0, i32 1 36 store i64 13, ptr %tmp3, align 8 37 %tmp4 = getelementptr inbounds %class.basic_string.11.42.73, ptr %arg, i64 0, i32 0, i32 0, i32 2, i32 1, i64 5 38 store i8 0, ptr %tmp4, align 1 39 tail call void @TestBar(ptr noalias sret(%class.basic_string.11.42.73) %arg) 40 ret void 41} 42 43; Function Attrs: argmemonly nounwind 44declare void @llvm.memcpy.p0.p0.i64(ptr nocapture, ptr nocapture readonly, i64, i1) #0 45 46attributes #0 = { argmemonly nounwind } 47