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Changed the documentation to reflect the new fastcall/cdecl reality.

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Greg King
2015-03-13 05:40:55 -04:00
parent a798b1d648
commit 604a5b4447
2 changed files with 60 additions and 34 deletions
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19
doc/customizing.sgml
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@@ -3,7 +3,7 @@
<article>
<title>Defining a Custom cc65 Target
<author>Bruce Reidenbach
<date>2010-02-22
<date>2015-03-13
<abstract>
This section provides step-by-step instructions on how to use the cc65
@@ -525,15 +525,16 @@ The first step in creating the assembly language code for the driver is
to determine how to pass the C arguments to the assembly language
routine. The cc65 toolset allows the user to specify whether the data
is passed to a subroutine via the stack or by the processor registers by
using the <tt>__fastcall__</tt> function declaration (note that there
are two underscore characters in front of and two behind the
<tt>fastcall</tt> declaration). When <tt>__fastcall__</tt> is
specified, the rightmost argument in the function call is passed to the
using the <tt/__fastcall__/ and <tt/__cdecl__/ function qualifiers (note that
there are two underscore characters in front of and two behind each
qualifier). <tt/__fastcall__/ is the default. When <tt/__cdecl__/ <em/isn't/
specified, and the function isn't variadic (i.e., its prototype doesn't have
an ellipsis), the rightmost argument in the function call is passed to the
subroutine using the 6502 registers instead of the stack. Note that if
there is only one argument in the function call, the execution overhead
required by the stack interface routines is completely avoided.
Without <tt>__fastcall__</tt>, the argument is loaded in the A and X
With <tt/__cdecl__</tt>, the last argument is loaded into the A and X
registers and then pushed onto the stack via a call to <tt>pushax</tt>.
The first thing the subroutine does is retrieve the argument from the
stack via a call to <tt>ldax0sp</tt>, which copies the values into the A
@@ -561,7 +562,7 @@ _foo: jsr ldax0sp ; Retrieve A and X from the stack
jmp incsp2 ; Pop A and X from the stack (includes return)
</verb></tscreen>
If <tt>__fastcall__</tt> is specified, the argument is loaded into the A
If <tt/__cdecl__/ isn't specified, then the argument is loaded into the A
and X registers as before, but the subroutine is then called
immediately. The subroutine does not need to retrieve the argument
since the value is already available in the A and X registers.
@@ -596,7 +597,7 @@ variable which is stored in the zero page memory space in order to allow
for retrieval of each character in the string via the indirect indexed
addressing mode.
The assembly language routine is stored in a file names
The assembly language routine is stored in a file named
&quot;rs232_tx.s&quot; and is shown below:
<tscreen><code>
@@ -680,7 +681,7 @@ all of the behind-the-scene work is transparent to the user.
#define TX_FIFO_FULL (FIFO_STATUS &amp; 0x01)
#define RX_FIFO_EMPTY (FIFO_STATUS &amp; 0x02)
extern void wait ();
extern void wait (void);
extern void __fastcall__ rs232_tx (char *str);
int main () {