Hello,
We speculate an insn in the PR but we do not make a check for it though we
should. The thing that broke this was the fix for PR 45472. In that pr,
we have moved a volatile insn too far up because we failed to merge the
bits describing its volatility when we have processed a control flow split.
The code to propagate the insn pattern with the insn merging was added
when the volatility of the two insns from the both split branches differ.
However, the volatility of the speculated insn and its original differ: the
original insn may trap while the speculated version may not. Thus, we
replace a speculative pattern with the original one per the PR 45472 fix
for no reason.
The patch for this problem just limits the original fix for PR 45472 to
apply for non-speculative insns only. There is no test as it is not so
easy to construct one -- we could count the number of speculation check in
the resulting assembly but there is no way to force speculation to happen.
Ok for trunk?
gcc/
2016-03-14 Andrey Belevantsev <a...@ispras.ru>
PR target/66660
* sel-sched-ir.c (merge_expr): Do not propagate trap bits into
speculative insns.
Best,
Andrey
commit 53ef39496acc26cc0021555e403068e93343aa20
Author: Andrey Belevantsev <a...@ispras.ru>
Date: Wed Jan 27 17:20:27 2016 +0300
Fix pr66660: do not propagate trap bits into speculative insns
diff --git a/gcc/sel-sched-ir.c b/gcc/sel-sched-ir.c
index e181cb9..ec59280 100644
--- a/gcc/sel-sched-ir.c
+++ b/gcc/sel-sched-ir.c
@@ -1871,12 +1871,12 @@ merge_expr (expr_t to, expr_t from, insn_t split_point)
/* Make sure that speculative pattern is propagated into exprs that
have non-speculative one. This will provide us with consistent
speculative bits and speculative patterns inside expr. */
- if ((EXPR_SPEC_DONE_DS (from) != 0
- && EXPR_SPEC_DONE_DS (to) == 0)
- /* Do likewise for volatile insns, so that we always retain
- the may_trap_p bit on the resulting expression. */
- || (VINSN_MAY_TRAP_P (EXPR_VINSN (from))
- && !VINSN_MAY_TRAP_P (EXPR_VINSN (to))))
+ if (EXPR_SPEC_DONE_DS (to) == 0
+ && (EXPR_SPEC_DONE_DS (from) != 0
+ /* Do likewise for volatile insns, so that we always retain
+ the may_trap_p bit on the resulting expression. */
+ || (VINSN_MAY_TRAP_P (EXPR_VINSN (from))
+ && !VINSN_MAY_TRAP_P (EXPR_VINSN (to)))))
change_vinsn_in_expr (to, EXPR_VINSN (from));
merge_expr_data (to, from, split_point);
