From: Christian Bruel <christian.bruel@st.com>
To: Bernd Schmidt <bschmidt@redhat.com>, "law@redhat.com" <law@redhat.com>
Cc: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
"Ramana.Radhakrishnan@arm.com"
<Ramana.Radhakrishnan@arm.com>,
"kyrylo.tkachov@arm.com" <kyrylo.tkachov@arm.com>,
"richard.earnshaw@arm.com" <richard.earnshaw@arm.com>
Subject: Re: [PATCH ARM]: PR67745: Fix function alignment after __attribute__ 2/2
Date: Wed, 07 Oct 2015 10:45:00 -0000 [thread overview]
Message-ID: <5614F7D0.8010409@st.com> (raw)
In-Reply-To: <5614F17B.5060402@redhat.com>
On 10/07/2015 12:18 PM, Bernd Schmidt wrote:
> On 10/07/2015 09:04 AM, Christian Bruel wrote:
>> + /* Similarly, relayout function's alignment if not forced. */
>> + if (!DECL_USER_ALIGN (fndecl)
>> + && (TREE_CODE (fntype) != METHOD_TYPE
>> + || TARGET_PTRMEMFUNC_VBIT_LOCATION != ptrmemfunc_vbit_in_pfn))
>> + DECL_ALIGN (fndecl) = FUNCTION_BOUNDARY;
>> }
>
> That's a very odd-looking condition. Why the vbit location test?
This is for member functions to make sure that the lsb address is
reserved for the virtual function bit.
see cp/decl.c:
/* If pointers to member functions use the least significant bit to
indicate whether a function is virtual, ensure a pointer
to this function will have that bit clear. */
if (TARGET_PTRMEMFUNC_VBIT_LOCATION == ptrmemfunc_vbit_in_pfn
&& TREE_CODE (type) == METHOD_TYPE
&& DECL_ALIGN (decl) < 2 * BITS_PER_UNIT)
DECL_ALIGN (decl) = 2 * BITS_PER_UNIT;
This happens for instance on i386 that aligns member functions on 2
bytes, bigger than the one byte required boundary. So we cannot
re-layout bellow that.
next prev parent reply other threads:[~2015-10-07 10:45 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-29 13:44 Christian Bruel
2015-09-29 13:59 ` Christian Bruel
2015-09-30 19:30 ` Jeff Law
2015-10-01 7:12 ` Christian Bruel
2015-10-01 16:11 ` Christian Bruel
2015-10-07 7:05 ` Christian Bruel
2015-10-07 10:18 ` Bernd Schmidt
2015-10-07 10:45 ` Christian Bruel [this message]
2015-10-07 17:37 ` Bernd Schmidt
2015-10-07 17:50 ` Bernd Schmidt
2015-10-08 13:14 ` Christian Bruel
2015-10-08 13:20 ` Bernd Schmidt
2015-10-08 13:51 ` Christian Bruel
2015-10-08 14:30 ` Bernd Schmidt
2015-10-12 10:56 ` Christian Bruel
2015-10-12 11:19 ` Bernd Schmidt
2015-10-12 11:26 ` Christian Bruel
2015-10-16 8:03 ` refactoring TARGET_PTRMEMFUNC_VBIT_LOCATION checks Christian Bruel
2015-10-16 9:47 ` Bernd Schmidt
2015-10-16 10:50 ` Christian Bruel
2015-10-16 10:56 ` Christian Bruel
2015-10-16 10:56 ` Bernd Schmidt
2015-10-13 8:03 ` [PATCH ARM]: PR67745: Fix function alignment after __attribute__ 2/2 Ramana Radhakrishnan
2015-10-13 10:18 ` Christian Bruel
2015-10-16 14:18 ` Christian Bruel
2015-10-08 14:01 ` Christian Bruel
2015-10-08 14:05 ` Bernd Schmidt
2015-10-07 17:40 ` Jeff Law
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