[p5sagit/p5-mst-13.2.git] / ext / B / ramblings / cc.notes

At entry to each basic block, the following can be assumed (and hence
must be forced where necessary at the end of each basic block):

The shadow stack @stack is empty.
For each lexical object in @pad, VALID_IV holds for each T_INT,
VALID_DOUBLE holds for each T_DOUBLE and VALID_SV holds otherwise.
The C shadow variable sp holds the stack pointer (not necessarily stack_sp).

write_back_stack
    Writes the contents of the shadow stack @stack back to the real stack.
    A write-back of each object in the stack is forced so that its
    backing SV contains the right value and that SV is then pushed onto the
    real stack. On return, @stack is empty.

write_back_lexicals
    Forces a write-back (i.e. achieves VALID_SV), where necessary, for each
    lexical object in @pad. Objects with the TEMPORARY flag are skipped. If
    write_back_lexicals is called with an (optional) argument, then it is
    taken to be a bitmask of more flags: any lexical object with one of those
    flags set is also skipped and not written back to its SV.

invalidate_lexicals($avoid)
    The VALID_INT and VALID_DOUBLE flags are turned off for each lexical
    object in @pad whose flags field doesn't overlap with $avoid.

reload_lexicals
    For each necessary lexical object in @pad, makes sure that VALID_IV
    holds for objects of type T_INT, VALID_DOUBLE holds for objects for
    type T_DOUBLE, and VALID_SV holds for other objects. An object is
    considered for reloading if its flags field does not overlap with the
    (optional) argument passed to reload_lexicals.
Commit	Line	Data
a8a597b2	1	At entry to each basic block, the following can be assumed (and hence
	2	must be forced where necessary at the end of each basic block):
	3
	4	The shadow stack @stack is empty.
	5	For each lexical object in @pad, VALID_IV holds for each T_INT,
	6	VALID_DOUBLE holds for each T_DOUBLE and VALID_SV holds otherwise.
	7	The C shadow variable sp holds the stack pointer (not necessarily stack_sp).
	8
	9	write_back_stack
	10	Writes the contents of the shadow stack @stack back to the real stack.
	11	A write-back of each object in the stack is forced so that its
	12	backing SV contains the right value and that SV is then pushed onto the
	13	real stack. On return, @stack is empty.
	14
	15	write_back_lexicals
	16	Forces a write-back (i.e. achieves VALID_SV), where necessary, for each
	17	lexical object in @pad. Objects with the TEMPORARY flag are skipped. If
	18	write_back_lexicals is called with an (optional) argument, then it is
	19	taken to be a bitmask of more flags: any lexical object with one of those
	20	flags set is also skipped and not written back to its SV.
	21
	22	invalidate_lexicals($avoid)
	23	The VALID_INT and VALID_DOUBLE flags are turned off for each lexical
	24	object in @pad whose flags field doesn't overlap with $avoid.
	25
	26	reload_lexicals
	27	For each necessary lexical object in @pad, makes sure that VALID_IV
	28	holds for objects of type T_INT, VALID_DOUBLE holds for objects for
	29	type T_DOUBLE, and VALID_SV holds for other objects. An object is
	30	considered for reloading if its flags field does not overlap with the
	31	(optional) argument passed to reload_lexicals.
	32