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Correct wrong check in simplify_stxi.

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* lib/lightning.c: Correct wrong check in simplify_stxi.
	The test was incorrectly comparing the target register
	and the displacement offset. This was a time bomb bug,
	that would trigger in code like:
		stxi Im0 Rb0 Rt0
		stxi Im1 Rb1 Rt1
	if Rb0 == Rb1 && Rt0 == Rt1 && Im0 == Rt1, that is,
	the wrong check was Im0 == Rt1, instead of the supposed
	Im0 == Imm1 (that was what the code mean't to do). It
	was removing the second stxi assuming it was redundantly
	generated; as that is not uncommon pattern on
	translators generating jit.
This commit is contained in:
Paulo Andrade 2015-02-03 15:19:21 -02:00
parent cdf5b785eb
commit 5724068b1c
2 changed files with 16 additions and 1 deletions
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15
ChangeLog
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@ -1,3 +1,18 @@
2015-02-03 Paulo Andrade <pcpa@gnu.org>
* lib/lightning.c: Correct wrong check in simplify_stxi.
The test was incorrectly comparing the target register
and the displacement offset. This was a time bomb bug,
that would trigger in code like:
stxi Im0 Rb0 Rt0
stxi Im1 Rb1 Rt1
if Rb0 == Rb1 && Rt0 == Rt1 && Im0 == Rt1, that is,
the wrong check was Im0 == Rt1, instead of the supposed
Im0 == Imm1 (that was what the code mean't to do). It
was removing the second stxi assuming it was redundantly
generated; as that is not uncommon pattern on
translators generating jit.
2015-02-02 Paulo Andrade <pcpa@gnu.org>
* configure.ac, include/lightning/jit_private.h,

2
lib/lightning.c
View file

@ -2790,7 +2790,7 @@ _simplify_stxi(jit_state_t *_jit, jit_node_t *prev, jit_node_t *node)
/* check for redundant store after load */
if (value->kind == jit_kind_code && value->code == node->code &&
value->base.q.l == right && value->base.q.h == _jitc->gen[right] &&
node->w.w == value->disp.w) {
node->u.w == value->disp.w) {
del_node(prev, node);
return (1);
}