[PATCH, AArch64, PR 61483] builtin va_start incorrectly initializes the field of va_list for incoming unnamed arguments on the stack

[Yufeng Zhang <Yufeng dot Zhang at arm dot com>]

Hi,

The patch fixes a bug in the AArch64 backend in calculating the 
beginning address of the unnamed incoming arguments on the stack, i.e. 
the initial value of __va_list->__stack.  aarch64_layout_arg incorrectly 
calculates the size of named arguments on stack using the number of 
registers needed as if there were enough registers available.  This is 
wrong, as for instance when passed in registers an HFA/HVA* argument 
takes as many SIMD registers as the number of its fields; when passed on 
the stack, however, it should be passed as what its storage layout is 
(rounded to the nearest multiple of 8 bytes).

The bug only affects builtin va_start, as it is other routines like 
aarch64_pad_arg_upward rather than aarch64_layout_arg which take care of 
the positioning of outgoing arguments on stack and the fetching of the 
incoming named arguments from stack.

The patch has passed bootstrapping.

OK for the trunk and 4.9.1 branch once the regtest passes as well?

Thanks,
Yufeng

* HFA: Homogeneous Floating-point Aggregate
  HVA: Homogeneous Short-Vector Aggregate


gcc/

	PR target/61483
	* config/aarch64/aarch64.c (aarch64_layout_arg): Add new local
	variable 'size'; calculate 'size' right in the front; use
	'size' to compute 'nregs' (when 'allocate_ncrn != 0') and
	pcum->aapcs_stack_words.

gcc/testsuite/

	PR target/61483
	* gcc.target/aarch64/aapcs64/type-def.h (struct hfa_fx2_t): New type.
	* gcc.target/aarch64/aapcs64/va_arg-13.c: New test.
	* gcc.target/aarch64/aapcs64/va_arg-14.c: Ditto.
	* gcc.target/aarch64/aapcs64/va_arg-15.c: Ditto.

Attachment: patch
Description: Text document