https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106816
Bug ID: 106816
Summary: noreturn/pure attributes are not set correctly on
multiversioned functions
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ipa
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc.gnu at vvalter dot com
CC: marxin at gcc dot gnu.org
Target Milestone: ---
During the investigation of PR106627, Richard noted (
https://gcc.gnu.org/pipermail/gcc-patches/2022-September/600777.html ) that
attributes like noreturn and pure on multiversioned functions are lost when the
function declaration is replaced by the dispatcher declaration in the same way
that the TREE_NOTHROW attribute got lost, which was fixed in PR106627.
Example:
__attribute__((noreturn,target("default")))
void f() {
for (;;) {}
}
__attribute__((noreturn,target("sse4.2,bmi")))
void f() {
for (;;) {}
}
int main()
{
f();
return 1;
}
Gcc should create no code after the call to f(), but the assembly output with
-O3 looks like the following:
call _Z5_Z1fvv@PLT
movl $1, %eax
addq $8, %rsp
.cfi_def_cfa_offset 8
ret
For a non-multiversioned function, no assembly instructions are generated after
the call instruction. Similar problems happen if the function is marked pure.
I reproduced this on 11.2.0 and 12.2, but this most likely affects all gcc
versions.
