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Add new 'switch' byte-code.

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'switch' takes two arguments from the stack: the variable to test, and
a jump table (implemented as a hash-table with the appropriate :test
function). By looking up the value of the variable in the hash table,
the interpreter can jump to the label pointed to by the value, if any.
This implementation can only be used for `cond' forms of the type
`(cond ((test x 'foo) 'bar) ...)`, such that the function `test` and
variable `x` is same for all clauses.

* lisp/emacs-lisp/bytecomp.el:

  * Add (byte-compile-cond-valid-obj2-p), (byte-compile-cond-vars),
    (byte-compile-cond-jump-table-info), (byte-compile-jump-table-add-tag),
    (byte-compile-cond-jump-table), byte-compile-jump-tables.

  * Add defcustom `byte-compile-cond-use-jump-table'.

  * (byte-compile-cond): Use them.

  * (byte-compile-lapcode): Patch tags present in jump tables, if any.

* lisp/emacs-lisp//byte-opt.el: (byte-optimize-lapcode): Add checks to
  some peephole optimizations to prevent them from messing up any code
  involving `byte-switch`.

* src/bytecode.c: (exec_byte_code): Add bytecode Bswitch.
This commit is contained in:
Vibhav Pant 2017-01-15 01:26:04 +05:30
parent 877c525f4b
commit 88549ec38e
3 changed files with 166 additions and 38 deletions
Download patch file Download diff file Expand all files Collapse all files

16
src/bytecode.c
View file

@ -267,6 +267,8 @@ DEFINE (Bstack_set, 0262) \
DEFINE (Bstack_set2, 0263) \
DEFINE (BdiscardN, 0266) \
\
DEFINE (Bswitch, 0267) \
\
DEFINE (Bconstant, 0300)
enum byte_code_op
@ -1411,6 +1413,20 @@ exec_byte_code (Lisp_Object bytestr, Lisp_Object vector, Lisp_Object maxdepth,
DISCARD (op);
NEXT;
CASE (Bswitch):
{
Lisp_Object jmp_table = POP;
Lisp_Object v1 = POP;
Lisp_Object dest = Fgethash(v1, jmp_table, Qnil);
if (!NILP(dest)) {
int car = XINT(XCAR(dest));
int cdr = XINT(XCDR(dest));
op = car + (cdr << 8); /* Simulate FETCH2 */
goto op_branch;
}
}
NEXT;
CASE_DEFAULT
CASE (Bconstant):
if (BYTE_CODE_SAFE