x86: fix under-aligned indirect AVX argument/return stack slots on win64 [PR54412]

x86: fix under-aligned indirect AVX argument/return stack slots on win64 [PR54412]

Fix x86 caller/callee handling for over-aligned indirect arguments/returns

On x86_64-w64-mingw32, TARGET_SEH limits MAX_SUPPORTED_STACK_ALIGNMENT
to 128 bits, but 256-bit AVX values are still passed and returned indirectly.
Some caller/callee stack-slot paths still used generic allocators that cap
requested alignment to MAX_SUPPORTED_STACK_ALIGNMENT, producing slots that are
under-aligned for later vmovapd/vmovaps accesses.

Fix caller-side paths by using dynamically allocated stack space for:

* over-aligned by-reference argument copies
* over-aligned hidden return slots

Fix callee-side paths by overallocating the local stack slot, then aligning the
effective address within that slot when required alignment exceeds
MAX_SUPPORTED_STACK_ALIGNMENT.

This preserves ABI behavior while ensuring alignment-sensitive AVX accesses are
correctly aligned in both caller and callee paths.

Use a target hook to control when this over-aligned stack-slot handling is
required, instead of hardcoding target conditionals in generic code.

gcc/ChangeLog:

	PR target/54412
	* target.def (overaligned_stack_slot_required): New calls hook.
	* calls.cc (allocate_call_dynamic_stack_space): New helper.
	(initialize_argument_information): Use
	targetm.calls.overaligned_stack_slot_required for over-aligned
	by-reference argument copies.
	(expand_call): Use
	targetm.calls.overaligned_stack_slot_required for over-aligned
	hidden return slots.
	* function.cc (assign_stack_local_aligned): New helper.
	(assign_parm_setup_block): Use
	targetm.calls.overaligned_stack_slot_required for over-aligned
	stack parm slots.
	(assign_parm_setup_reg): Likewise.
	* config/i386/i386.cc (ix86_overaligned_stack_slot_required): New.
	(TARGET_OVERALIGNED_STACK_SLOT_REQUIRED): Define for i386.
	* doc/tm.texi.in: Add hook placement.
	* doc/tm.texi: Regenerate.

Signed-off-by: oltolm <oleg.tolmatcev@gmail.com>
Signed-off-by: Jonathan Yong <10walls@gmail.com>