[Patch] PR56064: Fold VIEW_CONVERT_EXPR with FIXED_CST, Take #2

[Georg-Johann Lay]

Richard Biener wrote:
> Georg-Johann Lay wrote:
>> This is tentative patch as discussed in
>>
>> http://gcc.gnu.org/ml/gcc/2013-01/msg00187.html
>>
>> fold-const.c gets 2 new function native_encode_fixed and
>> native_interpret_fixed.  Code common with the integer case is factored out and
>> moved to the new constructor-like function double_int::from_buffer.
>>
>> The code bootstraps fine on x86-linux-gnu and I have test coverage from
>> avr-unknown-none.
>>
>> Ok to apply?
> 
> Ok.
> 
> Thanks,
> Richard.

Let me drop this, I don't like the name "const_fixed_from_double_int".  It's
bad and I think "fixed_from_double_int" is better.  Other constructor-like
functions for FIXED_VALUE_TYPE use fixed_from_* whereas const_fixed_* returns a
CONST_FIXED rtx.

This is less confusing and fits better the naming convention.

The new patch also adds const_fixed_from_double_int that actually returns a
CONST_FIXED rtx.  It's unused, but I would use it in the avr back.

Okay with that rename? (Or, at your option, without const_fixed_from_double_int).

Johann


	PR tree-optimization/56064
	* fixed-value.c (fixed_from_double_int): New function.
	* fixed-value.h (fixed_from_double_int): New prototype.
	(const_fixed_from_double_int): New static inline function.
	* fold-const.c (native_interpret_fixed): New static function.
	(native_interpret_expr) <FIXED_POINT_TYPE>: Use it.
	(can_native_interpret_type_p) <FIXED_POINT_TYPE>: Return true.
	(native_encode_fixed): New static function.
	(native_encode_expr) <FIXED_CST>: Use it.
	(native_interpret_int): Move double_int worker code to...
	* double-int.c (double_int::from_buffer): ...this new static method.
	* double-int.h (double_int::from_buffer): Prototype it.

testsuite/
	PR tree-optimization/56064
	* gcc.dg/fixed-point/view-convert.c: New test.



> 
>> There are less intrusive solutions that only handle the int <-> fixed cases,
>> for example fold-const.c:fold_view_convert_expr() could test for these cases
>> and use double_int directly without serializing / deserializing through a
>> memory buffer.
>>
>> Johann
>>
>>
>>         PR tree-optimization/56064
>>         * fixed-value.c (const_fixed_from_double_int): New function.
>>         * fixed-value.h (const_fixed_from_double_int): New prototype.
>>         * fold-const.c (native_interpret_fixed): New static function.
>>         (native_interpret_expr) <FIXED_POINT_TYPE>: Use it.
>>         (can_native_interpret_type_p) <FIXED_POINT_TYPE>: Return true.
>>         (native_encode_fixed): New static function.
>>         (native_encode_expr) <FIXED_CST>: Use it.
>>         (native_interpret_int): Move double_int worker code to...
>>         * double-int.c (double_int::from_buffer): ...this new static method.
>>         * double-int.h (double_int::from_buffer): Prototype it.
>>
>> testsuite/
>>         PR tree-optimization/56064
>>         * gcc.dg/fixed-point/view-convert.c: New test.
> 

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