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JIT: fix a bug related to self-tail calls

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The last argument in a self-tail cal is treated specially and
not immediately stored on the "runstack". Space was formerly
allocated for it, though, and under certain circumstances
that space was not initialized. I think a combination of thread
timing, GC timing, and flonum boxing could potentially lead to a
crash (but constructing a test case is really difficult).
This commit is contained in:
Matthew Flatt 2012-11-17 18:34:46 -07:00
parent 7a8f5f20fc
commit 4e6f8af667
1 changed files with 29 additions and 7 deletions
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36
src/racket/src/jitcall.c
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@ -1253,7 +1253,20 @@ static int generate_self_tail_call(Scheme_Object *rator, mz_jit_state *jitter, i
mz_set_local_p(JIT_R2, JIT_LOCAL2);
}
mz_rs_stxi(num_rands - 1, JIT_R0);
if (num_rands > 0) {
/* We didn't leave room for the last argument, so now we need to make
space for it. (Possible improvement: it may be possible to know that
room is available already, so that this isn't necessary.) */
mz_runstack_unskipped(jitter, 1);
mz_runstack_pushed(jitter, 1);
mz_rs_dec(1);
for (i = 0; i < num_rands-1; i++) {
mz_rs_ldxi(JIT_R1, i+1);
mz_rs_stxi(i, JIT_R1);
}
mz_rs_stxi(num_rands - 1, JIT_R0);
}
scheme_generate(rator, jitter, 0, 0, 0, JIT_V1, NULL);
CHECK_LIMIT();
mz_rs_sync();
@ -1818,10 +1831,19 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
if (inline_direct_args) {
mz_runstack_skipped(jitter, num_rands);
} else if (!direct_prim || (num_rands > 1) || (no_call == 2)) {
mz_rs_dec(num_rands);
need_safety = num_rands;
CHECK_RUNSTACK_OVERFLOW();
mz_runstack_pushed(jitter, num_rands);
int skip_end = 0;
if (direct_self && is_tail && !no_call && (num_rands > 0)) {
/* last argument is kept in a register */
skip_end = 1;
}
if (num_rands - skip_end > 0) {
mz_rs_dec(num_rands-skip_end);
CHECK_RUNSTACK_OVERFLOW();
mz_runstack_pushed(jitter, num_rands-skip_end);
}
need_safety = num_rands-skip_end;
if (skip_end)
mz_runstack_skipped(jitter, skip_end);
} else {
mz_runstack_skipped(jitter, 1);
}
@ -1933,8 +1955,8 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
mz_rs_ldxi(JIT_V1, i + offset);
}
if ((!direct_prim || (num_rands > 1) || (no_call == 2))
&& (!direct_self || !is_tail || no_call || (i + 1 < num_rands))
&& !inline_direct_args) {
&& (!direct_self || !is_tail || no_call || (i + 1 < num_rands))
&& !inline_direct_args) {
int reg = mz_CURRENT_REG_STATUS_VALID();
mz_rs_stxi(i + offset, JIT_R0);
mz_SET_REG_STATUS_VALID(reg);