Here is the current version of the patch with all the fixes. Regtested\bootstraped it on 64 bit.
We need a pointer since interrupt handler will update data pointing
to by frame. Since error_code isn't at the normal location where the
parameter is passed on stack and frame isn't in a hard register, we
changed ix86_function_arg:
+ if (!cum->caller && cfun->machine->func_type != TYPE_NORMAL)
+ {
+ /* The first argument of interrupt handler is a pointer and
+ points to the return address slot on stack. The optional
+ second argument is an integer for error code on stack. */
+ gcc_assert (type != NULL_TREE);
+ if (POINTER_TYPE_P (type))
+ {
+ if (cfun->machine->func_type == TYPE_EXCEPTION)
+ /* (AP) in the current frame in exception handler. */
+ arg = arg_pointer_rtx;
+ else
+ /* -WORD(AP) in the current frame in interrupt handler. */
+ arg = force_reg (Pmode,
+ plus_constant (Pmode, arg_pointer_rtx,
+ -UNITS_PER_WORD));
+ if (mode != Pmode)
+ arg = convert_to_mode (mode, arg, 1);
+ }
+ else
+ {
+ gcc_assert (TREE_CODE (type) == INTEGER_TYPE
+ && cfun->machine->func_type == TYPE_EXCEPTION
+ && mode == word_mode);
+ /* The error code is at -WORD(AP) in the current frame in
+ exception handler. */
+ arg = gen_rtx_MEM (word_mode,
+ plus_constant (Pmode, arg_pointer_rtx,
+ -UNITS_PER_WORD));
+ }
+
+ return arg;
+ }
+
to return a pseudo register. It violates
Return where to put the arguments to a function.
Return zero to push the argument on the stack, or a hard register in
which to store the argument.
Register allocator has no problem with parameters in pseudo registers.
But GCC crashes when it tries to access DECL_INCOMING_RTL as a hard
register when generating debug information. We worked around it by
doing
+
+ if (cfun->machine->func_type != TYPE_NORMAL)
+ {
+ /* Since the pointer argument of interrupt handler isn't a real
+ argument, adjust DECL_INCOMING_RTL for debug output. */
+ tree arg = DECL_ARGUMENTS (current_function_decl);
+ gcc_assert (arg != NULL_TREE
+ && POINTER_TYPE_P (TREE_TYPE (arg)));
+ if (cfun->machine->func_type == TYPE_EXCEPTION)
+ /* (AP) in the current frame in exception handler. */
+ DECL_INCOMING_RTL (arg) = arg_pointer_rtx;
+ else
+ /* -WORD(AP) in the current frame in interrupt handler. */
+ DECL_INCOMING_RTL (arg) = plus_constant (Pmode,
+ arg_pointer_rtx,
+ -UNITS_PER_WORD);
+ }
On Mon, Oct 5, 2015 at 12:29 PM, Uros Bizjak <ubiz...@gmail.com> wrote:
> On Mon, Oct 5, 2015 at 1:17 AM, H.J. Lu <hjl.to...@gmail.com> wrote:
>
>>>>>>> Looking a bit deeper into the code, it looks that we want to realign
>>>>>>> the stack in the interrupt handler. Let's assume that interrupt
>>>>>>> handler is calling some other function that saves SSE vector regs to
>>>>>>> the stack. According to the x86 ABI, incoming stack of the called
>>>>>>> function is assumed to be aligned to 16 bytes. But, interrupt handler
>>>>>>> violates this assumption, since the stack could be aligned to only 4
>>>>>>> bytes for 32bit and 8 bytes for 64bit targets. Entering the called
>>>>>>> function with stack, aligned to less than 16 bytes will certainly
>>>>>>> violate ABI.
>>>>>>>
>>>>>>> So, it looks to me that we need to realign the stack in the interrupt
>>>>>>> handler unconditionally to 16bytes. In this case, we also won't need
>>>>>>> the following changes:
>>>>>>>
>>>>>>
>>>>>> Current stack alignment implementation requires at least
>>>>>> one, maybe two, scratch registers:
>>>>>>
>>>>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67841
>>>>>>
>>>>>> Extend it to the interrupt handler, which doesn't have any scratch
>>>>>> registers may require significant changes in backend as well as
>>>>>> register allocator.
>>>>>
>>>>> But without realignment, the handler is unusable for anything but
>>>>> simple functions. The handler will crash when called function will try
>>>>> to save vector reg to stack.
>>>>>
>>>>
>>>> We can use unaligned load and store to avoid crash.
>>>
>>> Oh, sorry, I meant "called function will crash", like:
>>>
>>> -> interrupt when %rsp = 0x...8 ->
>>> -> interrupt handler ->
>>> -> calls some function that tries to save xmm reg to stack
>>> -> crash in the called function
>>>
>>
>> It should be fixed by this patch. But we need to fix stack
>> alignment in interrupt handler to avoid scratch register.
>>
>>
>> --
>> H.J.
>> ---
>> commit 15f48be1dc7ff48207927d0b835e593d058f695b
>> Author: H.J. Lu <hjl.to...@gmail.com>
>> Date: Sun Oct 4 16:14:03 2015 -0700
>>
>> Correctly set incoming stack boundary for interrupt handler
>>
>> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>> index 7ebdcd9..0f0cc3c 100644
>> --- a/gcc/config/i386/i386.c
>> +++ b/gcc/config/i386/i386.c
>> @@ -12037,8 +12037,11 @@ ix86_minimum_incoming_stack_boundary (bool sibcall)
>> {
>> unsigned int incoming_stack_boundary;
>>
>> + /* Stack of interrupt handler is always aligned to word_mode. */
>> + if (cfun->machine->func_type != TYPE_NORMAL)
>> + incoming_stack_boundary = TARGET_64BIT ? 64 : 32;
>
> Just a heads up that in order to support stack realignmnent on x86_64,
> MIN_STACK_BOUNDARY will soon be changed to BITS_PER_WORD, so you can
> use it in the line above. Please see comment #5 and #6 of PR 66697
> [1].
>
>> /* Prefer the one specified at command line. */
>> - if (ix86_user_incoming_stack_boundary)
>> + else if (ix86_user_incoming_stack_boundary)
>> incoming_stack_boundary = ix86_user_incoming_stack_boundary;
>> /* In 32bit, use MIN_STACK_BOUNDARY for incoming stack boundary
>> if -mstackrealign is used, it isn't used for sibcall check and
>
> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66697
>
> Uros.
patch
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