This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
[PATCH] combine: Fix PR84780 (more LOG_LINKS trouble)
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: gcc-patches at gcc dot gnu dot org
- Cc: zsojka at seznam dot cz, Segher Boessenkool <segher at kernel dot crashing dot org>
- Date: Mon, 12 Mar 2018 15:21:10 +0000
- Subject: [PATCH] combine: Fix PR84780 (more LOG_LINKS trouble)
- Authentication-results: sourceware.org; auth=none
There still are situations where we have stale LOG_LINKS. This causes
combine to try two-insn combinations I2->I3 where the register set by
I2 is used before I3 as well. Not good.
This patch fixes it by checking for this situation in can_combine_p
(similar to what we already do for three and four insn combinations).
Longer term we should make sure stale LOG_LINKS are removed (or moved),
or ideally we should use DF instead of LOG_LINKS.
I tested the patch on 31 architectures, no degradations seen. Zdenek
tested it on the original testcase (thanks!)
Committing to trunk.
Segher
2018-03-12 Segher Boessenkool <segher@kernel.crashing.org>
PR rtl-optimization/84169
PR rtl-optimization/84780
* combine.c (can_combine_p): Check for a 2-insn combination whether
the destination register is used between the two insns, too.
---
gcc/combine.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/gcc/combine.c b/gcc/combine.c
index c9105ed..06a9ddd 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -1990,6 +1990,7 @@ can_combine_p (rtx_insn *insn, rtx_insn *i3, rtx_insn *pred ATTRIBUTE_UNUSED,
&& (reg_used_between_p (dest, succ2, i3)
|| reg_used_between_p (dest, succ, succ2)))
|| (!succ2 && succ && reg_used_between_p (dest, succ, i3))
+ || (!succ2 && !succ && reg_used_between_p (dest, insn, i3))
|| (succ
/* SUCC and SUCC2 can be split halves from a PARALLEL; in
that case SUCC is not in the insn stream, so use SUCC2
--
1.8.3.1