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894a02412c
* doc/body.texi: Reorder documentation, making jit_frame and jit_tramp the lightning response to the need of trampolines, continuations and tail call optimizations. A pseudo code example of a factorial function was added. Also added a section for description of the available predicates. * doc/fact.c: New file, implementing a simple example of a translation of a trivial, recursive, tail call optimization into lightning calls. This is the conversion to functional C code of the example in doc/body.texi. * doc/Makefile.am: Update for the next test case.
75 lines
2.5 KiB
C
75 lines
2.5 KiB
C
#include <stdio.h>
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#include <lightning.h>
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static jit_state_t *_jit;
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typedef long (*pwfw_t)(long); /* Pointer to Long Function of Long */
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int main(int argc, char *argv[])
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{
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pwfw_t factorial;
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long arg;
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jit_node_t *ac; /* Accumulator */
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jit_node_t *in; /* Argument */
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jit_node_t *call;
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jit_node_t *fact;
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jit_node_t *jump;
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jit_node_t *fact_entry;
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jit_node_t *fact_out;
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init_jit(argv[0]);
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_jit = jit_new_state();
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/* declare a forward label */
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fact = jit_forward();
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jit_prolog(); /* Entry point of the factorial function */
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in = jit_arg(); /* Receive an integer argument */
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jit_getarg(JIT_R0, in); /* Move argument to RO */
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jit_prepare();
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jit_pushargi(1); /* This is the accumulator */
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jit_pushargr(JIT_R0); /* This is the argument */
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call = jit_finishi(NULL); /* Call the tail call optimized function */
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jit_patch_at(call, fact); /* Patch call to forward defined function */
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/* the above could have been written as:
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* jit_patch_at(jit_finishi(NULL), fact);
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*/
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jit_retval(JIT_R0); /* Fetch the result */
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jit_retr(JIT_R0); /* Return it */
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jit_epilog(); /* Epilog *before* label before prolog */
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/* define the forward label */
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jit_link(fact); /* Entry point of the helper function */
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jit_prolog();
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jit_frame(16); /* Reserve 16 bytes in the stack */
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fact_entry = jit_label(); /* This is the tail call entry point */
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ac = jit_arg(); /* The accumulator is the first argument */
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in = jit_arg(); /* The factorial argument */
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jit_getarg(JIT_R0, ac); /* Move the accumulator to R0 */
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jit_getarg(JIT_R1, in); /* Move the argument to R1 */
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fact_out = jit_blei(JIT_R1, 1); /* Done if argument is one or less */
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jit_mulr(JIT_R0, JIT_R0, JIT_R1); /* accumulator *= argument */
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jit_putargr(JIT_R0, ac); /* Update the accumulator */
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jit_subi(JIT_R1, JIT_R1, 1); /* argument -= 1 */
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jit_putargr(JIT_R1, in); /* Update the argument */
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jump = jit_jmpi();
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jit_patch_at(jump, fact_entry); /* Tail Call Optimize it! */
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jit_patch(fact_out);
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jit_retr(JIT_R0); /* Return the accumulator */
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factorial = jit_emit();
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/* no need to query information about resolved addresses */
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jit_clear_state();
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if (argc == 2)
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arg = atoi(argv[1]);
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else
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arg = 5;
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/* call the generated code */
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printf("factorial(%ld) = %ld\n", arg, factorial(arg));
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/* release all memory associated with the _jit identifier */
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jit_destroy_state();
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finish_jit();
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return 0;
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}
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