https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69891
Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #3 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
The problematic store is based on argp so it isn't killed by the memset, since
only those based on sp or fp are:
**scanning insn=20
mem: (symbol_ref:SI ("memset") [flags 0x41] <function_decl 0x7ffff6d1ee00
memset>)
after canon_rtx address: (symbol_ref:SI ("memset") [flags 0x41]
<function_decl 0x7ffff6d1ee00 memset>)
gid=1 offset=0
processing const load gid=1[0..1)
removing from active insn=19 has store
removing from active insn=18 has store
removing from active insn=17 has store
memset call 20
It's apparently a small loophole in the PR middle-end/31150 enhancement.
Index: dse.c
===================================================================
--- dse.c (revision 233545)
+++ dse.c (working copy)
@@ -2528,6 +2528,10 @@ scan_insn (bb_info_t bb_info, rtx_insn *
i_ptr = i_ptr->next_local_store;
}
+ /* But a call to memset clobbers memory so invalidates stores. It's
+ not only an optimization issue (the previous stores may be dead)
+ but also a correctness issue since the previous stores cannot be
+ seen as the source of the current value of the locations. */
if (memset_call)
{
rtx args[3];
@@ -2556,6 +2560,8 @@ scan_insn (bb_info_t bb_info, rtx_insn *
active_local_stores = insn_info;
}
}
+ else
+ add_non_frame_wild_read (bb_info);
}
}
else if (SIBLING_CALL_P (insn) && reload_completed)
Jakub, does this look good to you?
