https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86094
Bug ID: 86094
Summary: [8/9 Regression] Call ABI changed for small objects
with defaulted ctor
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Keywords: ABI, wrong-code
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: amonakov at gcc dot gnu.org
Target Milestone: ---
When compiling the following with -O2 -std=c++11:
struct S {
S(S&&) = default;
int i;
};
S foo(S s)
{
return s;
}
gcc-7 and earlier emit
_Z3foo1S:
movl %edi, %eax
ret
but gcc-8 and trunk emit
_Z3foo1S:
movl (%rsi), %edx
movq %rdi, %rax
movl %edx, (%rdi)
ret
i.e. the object is now passed in memory rather than on register. This appears
to be a silent ABI change.
(Clang generates the same code as gcc-7)
