[Ada] Expand integer-only implementation of ordinary fixed-point types

Pierre-Marie de Rodat derodat@adacore.com
Mon Nov 30 14:17:11 GMT 2020


This change relaxes the conditions under which the implementation of
ordinary fixed-point types uses only underlying integer instructions.

These conditions are on the Small of the ordinary fixed-point types,
which must now be a rational number whose factors are of a magnitude
bounded relatively to the size of the mantissa.

The algorithms of Image and Value are not modified, only that of Fore
is genezalized in a straightforward way.  Two new attributes are added
to the compiler, Small_Denominator and Small_Numerator, in order for
the Text_IO.Fixed_IO package to benefit from the enhancement.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* doc/gnat_rm/implementation_defined_attributes.rst (Pool_Address):
	Fix pasto.
	(Small_Denominator): New entry.
	(Small_Numerator): Likewise.
	* doc/gnat_rm/implementation_defined_characteristics.rst (3.5.9):
	Relax conditions on 128-bit smalls and integer-only implementation.
	* gnat_rm.texi: Regenerate.
	* exp_attr.adb (Expand_N_Attribute_Reference) <Attribute_Fore>:
	Relax conditions on integer implementation for ordinary fixed-point
	types and pass a third parameter to the routine.
	<Attribute_Small_Denominator>: Raise Program_Error.
	<Attribute_Small_Numerator>: Likewise.
	* exp_fixd.adb (Expand_Convert_Fixed_To_Fixed): Use a scaled divide
	if the numerator and denominator of the small ratio are sufficiently
	small integers.
	(Expand_Convert_Fixed_To_Integer): Use a scaled divide if numerator
	and denominator of the small value are sufficiently small integers.
	(Expand_Convert_Integer_To_Fixed): Likewise.
	* exp_imgv.adb (Expand_Image_Attribute): Relax the conditions on the
	integer implementation for ordinary fixed-point types.
	(Expand_Value_Attribute): Likewise.
	* freeze.adb (Freeze_Fixed_Point_Type): Relax conditions on 128-bit
	smalls.
	* sem_attr.adb (Analyze_Attribute) <Attribute_Small_Denominator>:
	Check no arguments, fixed-point and set type to Universal_Integer.
	<Attribute_Small_Numerator>: Likewise.
	(Eval_Attribute) <Attribute_Small_Denominator>: Fold statically.
	<Attribute_Small_Numerator>: Likewise.
	* snames.ads-tmpl (Name_Small_Denominator): New attribute name.
	(Name_Small_Numerator): Likewise.
	(Attribute_Id): Add Attribute_Small_{Denominator,Numerator}.
	* libgnat/a-tifiio.adb (Exact): Delete.
	(Need_64): Likewise.
	(OK_Get_32): New boolean constant.
	(OK_Put_32): Likewise.
	(OK_Get_64): Likewise.
	(OK_Put_64): Likewise.
	(E): Adjust.
	(Get procedures): Likewise.
	(Put procedures): Likewise.
	* libgnat/a-tifiio__128.adb (Exact): Delete.
	(Need_64): Likewise.
	(Need_128): Likewise.
	(OK_Get_32): New boolean constant.
	(OK_Put_32): Likewise.
	(OK_Get_64): Likewise.
	(OK_Put_64): Likewise.
	(OK_Get_128): Likewise.
	(OK_Put_128): Likewise.
	(E): Adjust.
	(Get procedures): Likewise.
	(Put procedures): Likewise.
	* libgnat/a-wtfiio.adb (Exact): Delete.
	(Need_64): Likewise.
	(OK_Get_32): New boolean constant.
	(OK_Put_32): Likewise.
	(OK_Get_64): Likewise.
	(OK_Put_64): Likewise.
	(E): Adjust.
	(Get procedures): Likewise.
	(Put procedures): Likewise.
	* libgnat/a-wtfiio__128.adb (Exact): Delete.
	(Need_64): Likewise.
	(Need_128): Likewise.
	(OK_Get_32): New boolean constant.
	(OK_Put_32): Likewise.
	(OK_Get_64): Likewise.
	(OK_Put_64): Likewise.
	(OK_Get_128): Likewise.
	(OK_Put_128): Likewise.
	(E): Adjust.
	(Get procedures): Likewise.
	(Put procedures): Likewise.
	* libgnat/a-ztfiio.adb (Exact): Delete.
	(Need_64): Likewise.
	(OK_Get_32): New boolean constant.
	(OK_Put_32): Likewise.
	(OK_Get_64): Likewise.
	(OK_Put_64): Likewise.
	(E): Adjust.
	(Get procedures): Likewise.
	(Put procedures): Likewise.
	* libgnat/a-ztfiio__128.adb (Exact): Delete.
	(Need_64): Likewise.
	(Need_128): Likewise.
	(OK_Get_32): New boolean constant.
	(OK_Put_32): Likewise.
	(OK_Get_64): Likewise.
	(OK_Put_64): Likewise.
	(OK_Get_128): Likewise.
	(OK_Put_128): Likewise.
	(E): Adjust.
	(Get procedures): Likewise.
	(Put procedures): Likewise.
	* libgnat/s-fore_f.ads (Fore_Fixed): Adjust signature.
	* libgnat/s-fore_f.adb (Fore_Fixed): Reimplement.
	* libgnat/s-fofi32.ads (Fore_Fixed32): Adjust signature.
	* libgnat/s-fofi64.ads (Fore_Fixed64): Likewise.
	* libgnat/s-fofi128.ads (Fore_Fixed128): Likewise.
	* libgnat/s-imagef.ads: Adjust description.
	* libgnat/s-imagef.adb (Maxdigs): Move around.
	(Set_Image_Integer): Remove assertion.
	* libgnat/s-valuef.ads: Adjust description.
	* libgnat/s-valuef.adb (Integer_To_Fixed): Minor tweak.
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