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gnat_ugn.texi (Calling Conventions): Document that the Intrinsic convention also allows access to named compiler...

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2008-05-23  Olivier Hainque  <hainque@adacore.com>

	* gnat_ugn.texi (Calling Conventions): Document that the Intrinsic
	convention also allows access to named compiler built-in subprograms
	such as the GCC __builtin family.

From-SVN: r135812
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Olivier Hainque 2008-05-23 16:33:46 +02:00 committed by Arnaud Charlet
parent bfc157d52c
commit 2e1c9cb460
1 changed files with 22 additions and 4 deletions
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gcc/ada/gnat_ugn.texi
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@ -2855,9 +2855,8 @@ This applies to an intrinsic operation, as defined in the Ada
Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
this means that the body of the subprogram is provided by the compiler itself,
usually by means of an efficient code sequence, and that the user does not
supply an explicit body for it. In an application program, the pragma can
only be applied to the following two sets of names, which the GNAT compiler
recognizes.
supply an explicit body for it. In an application program, the pragma may
be applied to the following sets of names:
@itemize @bullet
@item
@ -2868,7 +2867,9 @@ first one must be a signed integer type or a modular type with a binary
modulus, and the second parameter must be of type Natural.
The return type must be the same as the type of the first argument. The size
of this type can only be 8, 16, 32, or 64.
@item binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
@item
Binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
The corresponding operator declaration must have parameters and result type
that have the same root numeric type (for example, all three are long_float
types). This simplifies the definition of operations that use type checking
@ -2888,7 +2889,24 @@ This common idiom is often programmed with a generic definition and an
explicit body. The pragma makes it simpler to introduce such declarations.
It incurs no overhead in compilation time or code size, because it is
implemented as a single machine instruction.
@item
General subprogram entities, to bind an Ada subprogram declaration to
a compiler builtin by name with back-ends where such interfaces are
available. A typical example is the set of ``__builtin'' functions
exposed by the GCC back-end, as in the following example:
@smallexample @c ada
function builtin_sqrt (F : Float) return Float;
pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
@end smallexample
Most of the GCC builtins are accessible this way, and as for other
import conventions (e.g. C), it is the user's responsibility to ensure
that the Ada subprogram profile matches the underlying builtin
expectations.
@end itemize
@noindent
@ifset unw