https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58483
--- Comment #16 from dennis luehring <dl.soluz at gmx dot net> ---
the sample still gets reduced by clang to 160 with -O2 or -O3
clang:
main: # @main
mov eax, 160
ret
and gcc 11.2/trunk producing
-O2
main:
push rbp
mov edi, 12
sub rsp, 48
movq xmm15, QWORD PTR .LC0[rip]
mov DWORD PTR [rsp+8], 30
movq QWORD PTR [rsp], xmm15
pxor xmm15, xmm15
mov QWORD PTR [rsp+32], 0
movaps XMMWORD PTR [rsp+16], xmm15
call operator new(unsigned long)
mov rcx, QWORD PTR [rsp]
lea rdx, [rax+12]
lea rdi, [rsp+16]
mov QWORD PTR [rsp+16], rax
mov QWORD PTR [rsp+32], rdx
mov QWORD PTR [rax], rcx
mov ecx, DWORD PTR [rsp+8]
mov QWORD PTR [rsp+24], rdx
mov DWORD PTR [rax+8], ecx
call std::_Vector_base<int, std::allocator<int> >::~_Vector_base()
[base object destructor]
add rsp, 48
mov eax, 160
pop rbp
ret
mov rbp, rax
jmp .L5
main.cold:
.LC0:
.long 10
.long 20
-O3
main:
sub rsp, 24
mov edi, 12
movq xmm15, QWORD PTR .LC0[rip]
mov DWORD PTR [rsp+8], 30
movq QWORD PTR [rsp], xmm15
call operator new(unsigned long)
mov esi, 12
mov rdi, rax
mov rax, QWORD PTR [rsp]
mov QWORD PTR [rdi], rax
mov eax, DWORD PTR [rsp+8]
mov DWORD PTR [rdi+8], eax
call operator delete(void*, unsigned long)
mov eax, 160
add rsp, 24
ret
.LC0:
.long 10
.long 20
does that mean its still not clear if the unused new/delete can be removed
here?
