From 81e528bfffa44566ca6c93aae4acb407144fd241 Mon Sep 17 00:00:00 2001 From: Jeff Law Date: Sun, 21 Jul 2024 07:36:37 -0600 Subject: [PR rtl-optimization/115877] Fix livein computation for ext-dce So I'm not yet sure how I'm going to break everything down, but this is easy enough to break out as 1/N of ext-dce fixes/improvements. When handling uses in an insn, we first determine what bits are set in the destination which is represented in DST_MASK. Then we use that to refine what bits are live in the source operands. In the source operand handling section we *modify* DST_MASK if the source operand is a SUBREG (ugh!). So if the first operand is a SUBREG, then we can incorrectly compute which bit groups are live in the second operand, especially if it is a SUBREG as well. This was seen when testing a larger set of patches on the rl78 port (builtin-arith-overflow-p-7 & pr71631 execution failures), so no new test for this bugfix. Run through my tester (in conjunction with other ext-dce changes) on the various cross targets. Run individually through a bootstrap and regression test cycle on x86_64 as well. Pushing to the trunk. PR rtl-optimization/115877 gcc/ * ext-dce.cc (ext_dce_process_uses): Restore the value of DST_MASK for reach operand. --- gcc/ext-dce.cc | 2 ++ 1 file changed, 2 insertions(+) (limited to 'gcc') diff --git a/gcc/ext-dce.cc b/gcc/ext-dce.cc index 6d4b885..b4450e4 100644 --- a/gcc/ext-dce.cc +++ b/gcc/ext-dce.cc @@ -591,8 +591,10 @@ ext_dce_process_uses (rtx_insn *insn, rtx obj, bitmap live_tmp) making things live. Breaking from this loop will cause the iterator to work on sub-rtxs, so it is safe to break if we see something we don't know how to handle. */ + unsigned HOST_WIDE_INT save_mask = dst_mask; for (;;) { + dst_mask = save_mask; /* Strip an outer paradoxical subreg. The bits outside the inner mode are don't cares. So we can just strip and process the inner object. */ -- cgit v1.1