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* gnat_rm.texi (Machine Code Insertions): Clean up. 

From-SVN: r212844
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David Wohlferd 2014-07-19 10:55:28 +00:00 committed by Eric Botcazou
parent 49cc765db3
commit c6d27333f8
2 changed files with 24 additions and 14 deletions
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@ -1,3 +1,7 @@
2014-07-19 David Wohlferd <dw@LimeGreenSocks.com>
* gnat_rm.texi (Machine Code Insertions): Clean up.
2014-07-18 Robert Dewar <dewar@adacore.com>
* exp_ch7.adb: Minor reformatting.

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gcc/ada/gnat_rm.texi
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@ -20556,16 +20556,15 @@ including machine instructions in a subprogram.
The two features are similar, and both are closely related to the mechanism
provided by the asm instruction in the GNU C compiler. Full understanding
and use of the facilities in this package requires understanding the asm
instruction, see @ref{Extended Asm,, Assembler Instructions with C Expression
Operands, gcc, Using the GNU Compiler Collection (GCC)}.
instruction, see @ref{Extended Asm,,, gcc, Using the GNU Compiler
Collection (GCC)}.
Calls to the function @code{Asm} and the procedure @code{Asm} have identical
semantic restrictions and effects as described below. Both are provided so
that the procedure call can be used as a statement, and the function call
can be used to form a code_statement.
The first example given in the GCC documentation is the C @code{asm}
instruction:
Consider this C @code{asm} instruction:
@smallexample
asm ("fsinx %1 %0" : "=f" (result) : "f" (angle));
@end smallexample
@ -20591,12 +20590,15 @@ The @code{Asm_Output} attribute denotes a function that takes two
parameters. The first is a string, the second is the name of a variable
of the type designated by the attribute prefix. The first (string)
argument is required to be a static expression and designates the
constraint for the parameter (e.g.@: what kind of register is
required). The second argument is the variable to be updated with the
constraint (@pxref{Constraints,,, gcc, Using the GNU Compiler
Collection (GCC)})
for the parameter (e.g.@: what kind of register is required). The second
argument is the variable to be written or updated with the
result. The possible values for constraint are the same as those used in
the RTL, and are dependent on the configuration file used to build the
GCC back end. If there are no output operands, then this argument may
either be omitted, or explicitly given as @code{No_Output_Operands}.
No support is provided for GNU C's symbolic names for output parameters.
The second argument of @code{@var{my_float}'Asm_Output} functions as
though it were an @code{out} parameter, which is a little curious, but
@ -20613,8 +20615,9 @@ type designated by the prefix. The first (string) argument is required
to be a static expression, and is the constraint for the parameter,
(e.g.@: what kind of register is required). The second argument is the
value to be used as the input argument. The possible values for the
constant are the same as those used in the RTL, and are dependent on
constraint are the same as those used in the RTL, and are dependent on
the configuration file used to built the GCC back end.
No support is provided for GNU C's symbolic names for input parameters.
If there are no input operands, this argument may either be omitted, or
explicitly given as @code{No_Input_Operands}. The fourth argument, not
@ -20624,19 +20627,22 @@ expression, and is a space or comma separated list of names of registers
that must be considered destroyed as a result of the @code{Asm} call. If
this argument is the null string (the default value), then the code
generator assumes that no additional registers are destroyed.
In addition to registers, the special clobbers @code{memory} and
@code{cc} as described in the GNU C docs are both supported.
The fifth argument, not present in the above example, called the
@dfn{volatile} argument, is by default @code{False}. It can be set to
the literal value @code{True} to indicate to the code generator that all
optimizations with respect to the instruction specified should be
suppressed, and that in particular, for an instruction that has outputs,
the instruction will still be generated, even if none of the outputs are
used. @xref{Extended Asm,, Assembler Instructions with C Expression Operands,
suppressed, and in particular an instruction that has outputs
will still be generated, even if none of the outputs are
used. @xref{Volatile,,,
gcc, Using the GNU Compiler Collection (GCC)}, for the full description.
Generally it is strongly advisable to use Volatile for any ASM statement
that is missing either input or output operands, or when two or more ASM
statements appear in sequence, to avoid unwanted optimizations. A warning
is generated if this advice is not followed.
that is missing either input or output operands or to avoid unwanted
optimizations. A warning is generated if this advice is not followed.
No support is provided for GNU C's @code{asm goto} feature.
The @code{Asm} subprograms may be used in two ways. First the procedure
forms can be used anywhere a procedure call would be valid, and
@ -20662,7 +20668,7 @@ and more flexible. The code statement form is provided to meet the RM
suggestion that such a facility should be made available. The following
is the exact syntax of the call to @code{Asm}. As usual, if named notation
is used, the arguments may be given in arbitrary order, following the
normal rules for use of positional and named arguments)
normal rules for use of positional and named arguments:
@smallexample
ASM_CALL ::= Asm (