version 1.21, 2003/02/23 21:17:00
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version 1.22, 2003/02/25 22:58:49
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Line 96 Simple instructions
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Line 96 Simple instructions
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* C Code Macros:: Macros recognized by Vmgen |
* C Code Macros:: Macros recognized by Vmgen |
* C Code restrictions:: Vmgen makes assumptions about C code |
* C Code restrictions:: Vmgen makes assumptions about C code |
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* Stack growth direction:: is configurable per stack |
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Using the generated code |
Using the generated code |
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Line 715 stack-decl: 'stack ' ident ident ident
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Line 716 stack-decl: 'stack ' ident ident ident
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type-prefix-decl: |
type-prefix-decl: |
's" ' string '" ' ('single'|'double') ident 'type-prefix' ident |
's" ' string '" ' ('single'|'double') ident 'type-prefix' ident |
stack-prefix-decl: ident 'stack-prefix' string |
stack-prefix-decl: ident 'stack-prefix' string |
set-flag: 'store-optimization' ('on'|'off') |
set-flag: ('store-optimization'|'include-skipped-insts') ('on'|'off') |
@end example |
@end example |
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Note that the syntax of this code is not checked thoroughly (there are |
Note that the syntax of this code is not checked thoroughly (there are |
Line 737 are:
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Line 738 are:
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@findex stack-prefix |
@findex stack-prefix |
@findex store-optimization |
@findex store-optimization |
@example |
@example |
stack ( "name" "pointer" "type" -- ) |
stack ( "name" "pointer" "type" -- ) |
( name execution: -- stack ) |
( name execution: -- stack ) |
type-prefix ( addr u item-size stack "prefix" -- ) |
type-prefix ( addr u item-size stack "prefix" -- ) |
single ( -- item-size ) |
single ( -- item-size ) |
double ( -- item-size ) |
double ( -- item-size ) |
stack-prefix ( stack "prefix" -- ) |
stack-prefix ( stack "prefix" -- ) |
store-optimization ( -- addr ) |
store-optimization ( -- addr ) |
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include-skipped-insts ( -- addr ) |
@end example |
@end example |
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An @var{item-size} takes three cells on the stack. |
An @var{item-size} takes three cells on the stack. |
Line 803 Before we can use @code{data-stack} in t
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Line 805 Before we can use @code{data-stack} in t
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@cindex stack basic type |
@cindex stack basic type |
@cindex basic type of a stack |
@cindex basic type of a stack |
@cindex type of a stack, basic |
@cindex type of a stack, basic |
@cindex stack growth direction |
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This line defines the stack @code{data-stack}, which uses the stack |
This line defines the stack @code{data-stack}, which uses the stack |
pointer @code{sp}, and each item has the basic type @code{Cell}; other |
pointer @code{sp}, and each item has the basic type @code{Cell}; other |
types have to fit into one or two @code{Cell}s (depending on whether the |
types have to fit into one or two @code{Cell}s (depending on whether the |
type is @code{single} or @code{double} wide), and are cast from and to |
type is @code{single} or @code{double} wide), and are cast from and to |
Cells on accessing the @code{data-stack} with type cast macros |
Cells on accessing the @code{data-stack} with type cast macros |
(@pxref{VM engine}). Stacks grow towards lower addresses in |
(@pxref{VM engine}). By default, stacks grow towards lower addresses in |
Vmgen-erated interpreters. |
Vmgen-erated interpreters (@pxref{Stack growth direction}). |
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@cindex stack prefix |
@cindex stack prefix |
@cindex prefix, stack |
@cindex prefix, stack |
Line 846 first one (just as the intuition suggest
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Line 847 first one (just as the intuition suggest
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@menu |
@menu |
* C Code Macros:: Macros recognized by Vmgen |
* C Code Macros:: Macros recognized by Vmgen |
* C Code restrictions:: Vmgen makes assumptions about C code |
* C Code restrictions:: Vmgen makes assumptions about C code |
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* Stack growth direction:: is configurable per stack |
@end menu |
@end menu |
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@c -------------------------------------------------------------------- |
@c -------------------------------------------------------------------- |
Line 915 a C preprocessor macro.
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Line 917 a C preprocessor macro.
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@c -------------------------------------------------------------------- |
@c -------------------------------------------------------------------- |
@node C Code restrictions, , C Code Macros, Simple instructions |
@node C Code restrictions, Stack growth direction, C Code Macros, Simple instructions |
@subsection C Code restrictions |
@subsection C Code restrictions |
@cindex C code restrictions |
@cindex C code restrictions |
@cindex restrictions on C code |
@cindex restrictions on C code |
Line 975 macros can be implemented in several way
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Line 977 macros can be implemented in several way
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@samp{IP} points to the next instruction, and @samp{IPTOS} is its |
@samp{IP} points to the next instruction, and @samp{IPTOS} is its |
contents. |
contents. |
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@c -------------------------------------------------------------------- |
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@node Stack growth direction, , C Code restrictions, Simple instructions |
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@subsection Stack growth direction |
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@cindex stack growth direction |
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@cindex @code{stack-access-transform} |
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By default, the stacks grow towards lower addresses. You can change |
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this for a stack by setting the @code{stack-access-transform} field of |
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the stack to an xt @code{( itemnum -- index )} that performs the |
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appropriate index transformation. |
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E.g., if you want to let @code{data-stack} grow towards higher |
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addresses, with the stack pointer always pointing just beyond the |
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top-of-stack, use this right after defining @code{data-stack}: |
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@example |
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\E : sp-access-transform ( itemnum -- index ) negate 1- ; |
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\E ' sp-access-transform ' data-stack >body stack-access-transform ! |
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@end example |
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This means that @code{sp-access-transform} will be used to generate |
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indexes for accessing @code{data-stack}. The definition of |
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@code{sp-access-transform} above transforms n into -n-1, e.g, 1 into -2. |
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This will access the 0th data-stack element (top-of-stack) at sp[-1], |
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the 1st at sp[-2], etc., which is the typical way upward-growing |
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stacks are used. If you need a different transform and do not know |
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enough Forth to program it, let me know. |
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@c -------------------------------------------------------------------- |
@c -------------------------------------------------------------------- |
@node Superinstructions, Store Optimization, Simple instructions, Input File Format |
@node Superinstructions, Store Optimization, Simple instructions, Input File Format |
Line 1034 accesses a stack pointer should not be u
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Line 1063 accesses a stack pointer should not be u
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does not check these restrictions, they just result in bugs in your |
does not check these restrictions, they just result in bugs in your |
interpreter. |
interpreter. |
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@cindex include-skipped-insts |
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The Vmgen flag @code{include-skipped-insts} influences superinstruction |
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code generation. Currently there is no support in the peephole |
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optimizer for both variations, so leave this flag alone for now. |
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@c ------------------------------------------------------------------- |
@c ------------------------------------------------------------------- |
@node Store Optimization, Register Machines, Superinstructions, Input File Format |
@node Store Optimization, Register Machines, Superinstructions, Input File Format |
@section Store Optimization |
@section Store Optimization |
Line 1078 add1 ( n1 -- n1 )
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Line 1112 add1 ( n1 -- n1 )
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n2=n1+1; |
n2=n1+1; |
@end example |
@end example |
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Similarly, the store optimization assumes that the stack pointer is only |
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changed by Vmgen-erated code. If your C code changes the stack pointer, |
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use different names in input and output stack items to avoid a (probably |
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wrong) store optimization, or turn the store optimization off for this |
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VM instruction. |
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To turn on the store optimization, write |
To turn on the store optimization, write |
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@example |
@example |
Line 1177 expected by Vmgen (this should not happe
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Line 1217 expected by Vmgen (this should not happe
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line in a bug report). |
line in a bug report). |
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@cindex @code{syntax error, wrong char} error |
@cindex @code{syntax error, wrong char} error |
@cindex syntax error, wrong char |
@item syntax error, wrong char |
A syntax error. If you do not see right away where the error is, it may |
A syntax error. If you do not see right away where the error is, it may |
be helpful to check the following: Did you put an empty line in a VM |
be helpful to check the following: Did you put an empty line in a VM |
instruction where the C code is not delimited by braces (then the empty |
instruction where the C code is not delimited by braces (then the empty |
Line 1196 The stack item does not match any define
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Line 1236 The stack item does not match any define
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away any stack prefix). You should either declare the type prefix you |
away any stack prefix). You should either declare the type prefix you |
want for that stack item, or use a different type prefix |
want for that stack item, or use a different type prefix |
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@item @code{unknown primitive} error |
@cindex @code{unknown primitive} error |
@item unknown primitive |
@item unknown primitive |
You have used the name of a simple VM instruction in a superinstruction |
You have used the name of a simple VM instruction in a superinstruction |
definition without defining the simple VM instruction first. |
definition without defining the simple VM instruction first. |
Line 1386 type. For @samp{inst-stream}, the name
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Line 1426 type. For @samp{inst-stream}, the name
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plain r-value; typically it is a macro that abstracts away the |
plain r-value; typically it is a macro that abstracts away the |
differences between the various implementations of @code{NEXT_P*}. |
differences between the various implementations of @code{NEXT_P*}. |
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@cindex IMM_ARG |
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@findex IMM_ARG |
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@item IMM_ARG(access,value) |
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Define this to expland to ``(access)''. This is just a placeholder for |
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future extensions. |
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@cindex top of stack caching |
@cindex top of stack caching |
@cindex stack caching |
@cindex stack caching |
@cindex TOS |
@cindex TOS |