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diff --git a/doc/supplements/i960/callconv.t b/doc/supplements/i960/callconv.t deleted file mode 100644 index d112e67123..0000000000 --- a/doc/supplements/i960/callconv.t +++ /dev/null @@ -1,97 +0,0 @@ -@c -@c COPYRIGHT (c) 1988-2002. -@c On-Line Applications Research Corporation (OAR). -@c All rights reserved. -@c -@c $Id$ -@c - -@chapter Calling Conventions - -@section Introduction - -Each high-level language compiler generates -subroutine entry and exit code based upon a set of rules known -as the compiler's calling convention. These rules address the -following issues: - -@itemize @bullet -@item register preservation and usage - -@item parameter passing - -@item call and return mechanism -@end itemize - -A compiler's calling convention is of importance when -interfacing to subroutines written in another language either -assembly or high-level. Even when the high-level language and -target processor are the same, different compilers may use -different calling conventions. As a result, calling conventions -are both processor and compiler dependent. - -@section Processor Background - -All members of the i960 architecture family support -two methods for performing procedure calls: a RISC-style -branch-and-link and an integrated call and return mechanism. - -On a branch-and-link, the processor branches to the -invoked procedure and saves the return address in a register, -@code{G14}. Typically, the invoked procedure will not invoke another -procedure and is referred to as a leaf procedure. Many -high-level language compilers for the i960 family recognize leaf -procedures and automatically optimize them to utilize the -branch-and-link mechanism. Branch-and-link procedures are -invoked using the @code{bal} and @code{balx} instructions and return control -via the @code{bx} instruction. By convention, @code{G14} is zero when not in -a leaf procedure. It is the responsibility of the leaf -procedure to clear @code{G14} before returning. - -The integrated call and return mechanism also -branches to the invoked procedure and saves the return address -as did the branch and link mechanism. However, the important -difference is that the @code{call}, @code{callx}, and @code{calls} instructions save -the local register set (@code{R0} through @code{R15}) before transferring -control to the invoked procedure. The @code{ret} instruction -automatically restores the previous local register set. The -i960CA provides a register cache which can be configured to -retain the last five to sixteen recent register caches. When -the register cache is full, the oldest cached register set is -written to the stack. - -@section Calling Mechanism - -All RTEMS directives are invoked using either a @code{call} -or @code{callx} instruction and return to the user via the @code{ret} -instruction. - -@section Register Usage - -As discussed above, the @code{call} and @code{callx} instructions -automatically save the current contents of the local register -set (@code{R0} through @code{R15}). The contents of the local registers will -be restored as part of returning to the application. The -contents of global registers @code{G0} through @code{G7} are not preserved by -RTEMS directives. - -@section Parameter Passing - -RTEMS uses the standard i960 family C parameter -passing mechanism in which @code{G0} contains the first parameter, @code{G1} -the second, and so on for the remaining parameters. No RTEMS -directive requires more than six parameters. - -@section User-Provided Routines - -All user-provided routines invoked by RTEMS, such as -user extensions, device drivers, and MPCI routines, must also -adhere to these calling conventions. - -@section Leaf Procedures - -RTEMS utilizes leaf procedures internally to improve -performance. This improves execution speed as well as reducing -stack usage and the number of register sets which must be cached. - - |