Re: [PATCH] Sanitizing the middle-end interface to the back-end for strict alignment

[Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>]

On 8/28/19 10:38 AM, Bernd Edlinger wrote:
> On 8/27/19 11:25 AM, Kyrill Tkachov wrote:
>> Hi Bernd,
>>
>> On 8/15/19 8:47 PM, Bernd Edlinger wrote:
>>> Hi,
>>>
>>> this is the split out part from the "Fix not 8-byte aligned ldrd/strd on ARMv5 (PR 89544)"
>>> which is sanitizing the middle-end interface to the back-end for strict alignment,
>>> and a couple of bug-fixes that are necessary to survive boot-strap.
>>> It is intended to be applied after the PR 89544 fix.
>>>
>>> I think it would be possible to change the default implementation of STACK_SLOT_ALIGNMENT
>>> to make all stack variables always naturally aligned instead of doing that only
>>> in assign_parm_setup_stack, but would still like to avoid changing too many things
>>> that do not seem to have a problem.  Since this would affect many targets, and more
>>> kinds of variables that may probably not have a strict alignment problem.
>>> But I am ready to take your advice though.
>>>
>>>
>>> Boot-strapped and reg-tested on x86_64-pc-linux-gnu and arm-linux-gnueabihf
>>> Is it OK for trunk?
>> I'm not opposed to the checks but...
>>
>>
>>> Thanks
>>> Bernd.
>>>
>> Index: gcc/config/arm/vec-common.md
>> ===================================================================
>> --- gcc/config/arm/vec-common.md    (Revision 274531)
>> +++ gcc/config/arm/vec-common.md    (Arbeitskopie)
>> @@ -26,6 +26,12 @@
>>     "TARGET_NEON
>>      || (TARGET_REALLY_IWMMXT && VALID_IWMMXT_REG_MODE (<MODE>mode))"
>>   {
>> +  gcc_checking_assert (!MEM_P (operands[0])
>> +               || MEM_ALIGN (operands[0])
>> +              >= GET_MODE_ALIGNMENT (<MODE>mode));
>> +  gcc_checking_assert (!MEM_P (operands[1])
>> +               || MEM_ALIGN (operands[1])
>> +              >= GET_MODE_ALIGNMENT (<MODE>mode));
>>     if (can_create_pseudo_p ())
>>       {
>>         if (!REG_P (operands[0]))
>>
>> ... can we please factor the (!MEM_P (operands[0]) || MEM_ALIGN (operands[0]) >= GET_MODE_ALIGNMENT (<MODE>mode)) checks into a common function and use that?
>>
> Sure, good idea.  How about converting it to a predicate?
> This creates 1:1 equivalent code to the open coded assertions.
>
> Is it OK for trunk?
>
>
> Thanks
> Bernd.


patch-strict-align.diff

2019-08-15  Bernd Edlinger<bernd.edlinger@hotmail.de>
	    Richard Biener<rguenther@suse.de>

	* expr.c (expand_assignment): Handle misaligned DECLs.
	(expand_expr_real_1): Handle FUNCTION_DECL as unaligned.
	* function.c (assign_parm_adjust_stack_rtl): Check movmisalign optab
	too.
	(assign_parm_setup_stack): Allocate properly aligned stack slots.
	* varasm.c (build_constant_desc): Align constants of misaligned types.
	* config/arm/predicates.md (aligned_operand): New predicate.
	* config/arm/arm.md (movdi, movsi, movhi, movhf, movsf, movdf): Use
	sligned_operand to check restrictions on memory addresses.

typo in "aligned_operand"

         * config/arm/neon.md (movti, mov<VSTRUCT>, mov<VH>): Likewise.
	* config/arm/vec-common.md (mov<VALL>): Likewise.


Looks good now.

Ok, thanks!

Kyrill