From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-472497-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 25939 invoked by alias); 8 Jan 2015 16:46:58 -0000
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
Received: (qmail 25858 invoked by uid 48); 8 Jan 2015 16:46:49 -0000
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/64536] [4.9/5 Regression] Undefined .L* symbol starting with jump2 on s390x
Date: Thu, 08 Jan 2015 16:46:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 5.0
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jakub at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 4.9.3
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields: attachments.created
Message-ID: <bug-64536-4-vC6SSMRbyg@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-64536-4@http.gcc.gnu.org/bugzilla/>
References: <bug-64536-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-SW-Source: 2015-01/txt/msg00491.txt.bz2

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64536

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 34404
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34404&action=edit
gcc5-pr64536.patch

Given that tidy_fallthru_edge seems to be called only rarely, I think adding
too much code to handle tablejumps with single successor is not a good idea.

So I think we should just give up on tablejumps there.  And perhaps make sure
we optimize single successor tablejumps somewhere else, where it is run often
enough that it will be actually beneficial.

E.g.
int a;
#define A(n) case n: a++; break;
#define B(n) A(n##0) A(n##1) A(n##2) A(n##3) A(n##4) \
A(n##5) A(n##6) A(n##7) A(n##8) A(n##9)
#define C(n) B(n##0) B(n##1) B(n##2) B(n##3) B(n##4) \
B(n##5) B(n##6) B(n##7) B(n##8) B(n##9)

void
foo (int x)
{
  switch (x)
    {
    C(1)
    }
}

on x86_64 with -O2 or -O2 -fpic isn't optimized, because tidy_fallthru_edges
isn't called and so we do not even attempt to do anything about it.
On the s390x testcase it is called just because some other cleanup in another
part of the function created unreachable blocks that need cleanup.
And, wonder why tree-ssa-tail-merge.c doesn't want to optimize this.  Perhaps
it gives up because of the load and store?