On 7/30/19 4:00 PM, Marc Glisse wrote:
> On Tue, 30 Jul 2019, Martin Liška wrote:
>
>> Ah, that's bad, both of them need a care:
>
> Yes, that makes more sense to me, thanks.
>
>>> I tried to experiment to understand, but it is complicated because
>>> including <new> disables the optimization:
>>>
>>> #include <new>
>>> void fn1() {
>>> char*p=new char;
>>> delete p;
>>> }
>>>
>>> This ICEs with -O -std=c++17:
>>>
>>> int a = 64;
>>> std::align_val_t b{64};
>>> void fn1() {
>>> void *s = operator new(a,b);
>>> operator delete(s,8+*(unsigned long*)s,b);
>>> }
>>>
>>>
>>
>> I can't see it on current master. Can you?
>
> Yes. I just did a clean build to make sure.
>
That's addressed in a patch I'm attaching.
Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
Ready to be installed?
Thanks,
Martin
>From cd975aaccbbed3c03bbd246e0802c94693a0962d Mon Sep 17 00:00:00 2001
From: Martin Liska <[email protected]>
Date: Tue, 30 Jul 2019 15:40:24 +0200
Subject: [PATCH] Mark necessary 2nd and later args for delete op.
gcc/ChangeLog:
2019-07-30 Martin Liska <[email protected]>
* tree-ssa-dce.c (propagate_necessity): Delete operator can
have size and (or) alignment as 2nd and later arguments.
Mark all of them as necessary.
---
gcc/tree-ssa-dce.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index bec13cd5930..80d5f5c30f7 100644
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -824,13 +824,16 @@ propagate_necessity (bool aggressive)
|| DECL_FUNCTION_CODE (def_callee) == BUILT_IN_CALLOC))
|| DECL_IS_REPLACEABLE_OPERATOR_NEW_P (def_callee)))
{
- /* Some delete operators have size as 2nd argument. */
+ /* Delete operators can have alignment and (or) size as next
+ arguments. When being a SSA_NAME, they must be marked
+ as necessary. */
if (is_delete_operator && gimple_call_num_args (stmt) >= 2)
- {
- tree size_argument = gimple_call_arg (stmt, 1);
- if (TREE_CODE (size_argument) == SSA_NAME)
- mark_operand_necessary (size_argument);
- }
+ for (unsigned i = 1; i < gimple_call_num_args (stmt); i++)
+ {
+ tree arg = gimple_call_arg (stmt, i);
+ if (TREE_CODE (arg) == SSA_NAME)
+ mark_operand_necessary (arg);
+ }
continue;
}
--
2.22.0
