This is both an ICE and an ABI bug dating back to the implementation of the 
64-bit calling conventions in 1998: for structures larger than 8 bytes and not 
larger than 16 bytes containing a FP field in the second half and passed in 
slot #15 of the parameter array, the compiler passes the FP field in the %f32 
register instead of on the stack; this results in an ICE for a 'float' and an 
ABI bug for a 'double'.

The attached fix implements the detection and the handling of this case and 
shouldn't change anything in the other cases; however, since the existing code 
was suffering from excessive duplication (structure traversal was implemented 
3 times, handling of FP fields twice and handling of integer fields 3 times), 
the code refactors the whole thing and in particular uses a function template 
for the traversal, which is then instantiated 3 times.

Bootstrapped/regtested on SPARC64/Solaris and also compat-regtested (both bugs 
are rare enough as to go unnoticed by the compat testsuite).  I also verified 
manually that GCC is now compatible with Sun CC in this case too.

I'll document the ABI change in changes.html separately.


2016-02-29  Eric Botcazou  <ebotcazou@adacore.com>

	PR target/69706
	* config/sparc/sparc.c (ROUND_ADVANCE): Rename to...
	(NWORDS_UP): ...this
	(init_cumulative_args): Minor tweaks.
	(sparc_promote_function_mode): Likewise.
	(scan_record_type): Delete.
	(traverse_record_type): New function template.
	(classify_data_t): New structure type.
	(classify_registers): New inline function.
	(function_arg_slotno): In 64-bit mode, bail out early if FP slots are
	exhausted.  Instantiate traverse_record_type on classify_registers and
	deal with the case of a structure passed in slot #15 with no FP field
	in the first word.
	(assign_data_t): New structure type.
	(compute_int_layout): New static function.
	(compute_fp_layout): Likewise.
	(count_registers): New inline function.
	(assign_int_registers): New static function.
	(assign_fp_registers): Likewise.
	(assign_registers): New inline function.
	(function_arg_record_value_1): Delete.
	(function_arg_record_value_2): Likewise.
	(function_arg_record_value_3): Likewise.
	(function_arg_record_value): Adjust to above changes.  Instantiate
	traverse_record_type on count_registers to first count the number of
	registers to be used and then on assign_registers to assign them.
	(function_arg_union_value): Adjust to above renaming.
	(sparc_function_arg_1); Minor tweaks.  Remove commented out code.
	(sparc_arg_partial_bytes): Adjust to above renaming.  Deal with the
	case of a structure passed in slot #15
	(sparc_function_arg_advance): Likewise.
	(function_arg_padding): Minor tweak.


2016-02-29  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc.target/sparc/20160229-1.c: New test.

-- 
Eric Botcazou