[Ada] Implement 'Valid_Value attribute

gcc/ada/

	* libgnat/s-valuen.ads, libgnat/s-valuen.adb
	(Value_Enumeration_Pos): New function to compute the 'Pos of the
	enumeration literal for a given String.  Return a special value
	instead of raising an exception on invalid input. Called by both
	Valid_Enumeration_Image and Value_Enumeration.
	(Valid_Enumeration_Image): Return a Boolean indicating whether
	the String is a valid Image for the given enumeration type.
	(Value_Enumeration): Implement in terms of
	Value_Enumeration_Pos.
	* libgnat/s-vaenu8.ads, libgnat/s-vaen16.ads,
	libgnat/s-vaen32.ads: Rename Valid_Enumeration_Image from the
	instances.
	* libgnat/s-valuti.ads: Correct documentation (it was not true
	for the null string).
	* libgnat/s-valuti.adb (Normalize_String): Do not raise
	Constraint_Error for the null string, nor strings containing
	nothing but blanks, so that Valid_Enumeration_Image can return
	False in these cases, rather than raising an exception.
	* rtsfind.ads (RE_Value_Enumeration_8, RE_Value_Enumeration_16,
	RE_Value_Enumeration_32): New functions.
	(RTE_Available): Improve comment (E doesn't have to be a
	subprogram, although that's the usual case).
	* sem_attr.adb (nalid_Value): Semantic analysis for new
	attribute.
	* exp_attr.adb: Call Expand_Valid_Value_Attribute for new
	attribute.
	* exp_imgv.ads, exp_imgv.adb (Expand_Valid_Value_Attribute): New
	procedure to expand Valid_Value into a call to
	Valid_Enumeration_Image_NN.
	(Expand_Value_Attribute): Misc code cleanups.  Remove two ???
	mark comments. RTE_Available won't work here.  For one thing,
	RTE_Available (X) shouldn't be called until the compiler has
	decided to make use of X (see comments on RTE_Available), and in
	this case we're trying to AVOID calling something.
	* snames.ads-tmpl: New attribute name.
	* doc/gnat_rm/implementation_defined_attributes.rst: Document
	new attribute.
	* gnat_rm.texi: Regenerate.

1 files changed, 18 insertions, 7 deletions

diff --git a/gcc/ada/rtsfind.ads b/gcc/ada/rtsfind.ads
index ef17cf2..28d14bd 100644
--- a/gcc/ada/rtsfind.ads
+++ b/gcc/ada/rtsfind.ads
@@ -2036,9 +2036,13 @@ package Rtsfind is
 
      RE_Value_Decimal128,                -- System_Val_Decimal_128
 
-     RE_Value_Enumeration_8,             -- System.Val_Enum
-     RE_Value_Enumeration_16,            -- System.Val_Enum
-     RE_Value_Enumeration_32,            -- System.Val_Enum
+     RE_Value_Enumeration_8,             -- System.Val_Enum_8
+     RE_Value_Enumeration_16,            -- System.Val_Enum_16
+     RE_Value_Enumeration_32,            -- System.Val_Enum_32
+
+     RE_Valid_Enumeration_Value_8,       -- System.Val_Enum_8
+     RE_Valid_Enumeration_Value_16,      -- System.Val_Enum_16
+     RE_Valid_Enumeration_Value_32,      -- System.Val_Enum_32
 
      RE_Value_Fixed32,                   -- System_Val_Fixed_32
 
@@ -3726,6 +3730,12 @@ package Rtsfind is
 
      RE_Value_Enumeration_32             => System_Val_Enum_32,
 
+     RE_Valid_Enumeration_Value_8        => System_Val_Enum_8,
+
+     RE_Valid_Enumeration_Value_16       => System_Val_Enum_16,
+
+     RE_Valid_Enumeration_Value_32       => System_Val_Enum_32,
+
      RE_Value_Fixed32                    => System_Val_Fixed_32,
 
      RE_Value_Fixed64                    => System_Val_Fixed_64,
@@ -4074,10 +4084,11 @@ package Rtsfind is
    --  and without generating an error message, i.e. if the call will obtain
    --  the desired entity without any problems.
    --
-   --  If we call this and it returns True, we should generate a call to E.
-   --  In other words, the compiler should not call RTE_Available (E) until
-   --  it has decided it wants to generate a call to E. Otherwise we can get
-   --  spurious dependencies and elaboration orders.
+   --  If we call this and it returns True, we should generate a reference to
+   --  E (usually a call). In other words, for a subprogram E, the compiler
+   --  should not call RTE_Available (E) until it has decided it wants to
+   --  generate a call to E. Otherwise we can get spurious dependencies and
+   --  elaboration orders.
    --
    --     if RTE_Available (E) -- WRONG!
    --       and then <some condition>