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Re: optimization/7409: loop optimization
- From: Bernhard Kaindl <bk at suse dot de>
- To: <hpenner at de dot ibm dot com>
- Cc: <gcc-gnats at gcc dot gnu dot org>, <mark at codesourcery dot com>,<uweigand at de dot ibm dot com>, <nobody at gcc dot gnu dot org>, <gcc-prs at gcc dot gnu dot org>,<gcc-bugs at gcc dot gnu dot org>, Reinhard Max <max at suse dot de>
- Date: Fri, 26 Jul 2002 14:11:51 +0200 (CEST)
- Subject: Re: optimization/7409: loop optimization
On 25 Jul 2002 hpenner@de.ibm.com wrote:
> >Description:
> loop_optimize deletes an insn, which should not be deleted.
> This leads to a abort of an application (tcl).
Yes, it leads to an abort in different 8.x tcl versions when
running the included testsuite on s390x with gcc-3.1.1-cvs,
but it looks like it can be worked around by changing the
-O1 in the Makefile ot -O0 or -O2.
Just to bring all the info together, I append some mails
also describing the problem, a testcase and a proposed fix.
---------- Forwarded message ----------
From: Hartmut Penner <HPENNER@de.ibm.com>
To: mark@codesourcery.com, gcc-patches@gcc.gnu.org
Cc: uweigand@de.ibm.com
Date: Thu, 25 Jul 2002 19:53:53 +0200
Subject: PR 7409/Loop optimization bug patch
A proposed patch for problem described in PR7409 is appended here.
The problem was, that the usage of a register as a parameter was not taken
into acount in the function find_single_use_in_loop.
Index: loop.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/loop.c,v
retrieving revision 1.389.2.7
diff -u -r1.389.2.7 loop.c
--- loop.c 15 Jun 2002 01:12:04 -0000 1.389.2.7
+++ loop.c 25 Jul 2002 17:41:28 -0000
@@ -3448,6 +3448,19 @@
const char *fmt = GET_RTX_FORMAT (code);
int i, j;
+ if (x == PATTERN (insn) && GET_CODE (insn) == CALL_INSN)
+ {
+ rtx link;
+ for (link = CALL_INSN_FUNCTION_USAGE (insn); link; link = XEXP (link, 1))
+ {
+ rtx op, reg;
+
+ if (GET_CODE (op = XEXP (link, 0)) == USE
+ && GET_CODE (reg = XEXP (op, 0)) == REG)
+ regs->array[REGNO (reg)].single_usage = const0_rtx;
+ }
+ }
+
if (code == REG)
regs->array[REGNO (x)].single_usage
= (regs->array[REGNO (x)].single_usage != 0
Mit freundlichem Gruß / Best regards,
Hartmut Penner
GCC for S/390 Development
---------- Forwarded message ----------
The testcase is from Tcl and is accessibel there under the name tclUtil
which is the file where the problem appears:
http://www.suse.de/~bk/gcc/testcases/
cc -S -g -O1 -fPIC tclUtil.i
This is the assembler code generated to call TclFindElement (only one
place in the file):
lgfr %r4,%r8
la %r1,184(%r15)
stg %r1,160(%r15)
la %r1,188(%r15)
stg %r1,168(%r15)
lg %r2,200(%r15)
lgr %r3,%r10
la %r5,192(%r15)
+ la %r6,176(%r15)
brasl %r14,TclFindElement@PLT
Adding the line marked with + fixes the passing of a pointer onto the
stack and fixes this particulare case.
There are other cases on tcl which -O1 also cause segementation violations,
I hope that the other cases are also fixed with the patch above, it's likely
that the conditions of the other uses of TclFindElement are similar.
Best Regards
Bernhard Kaindl
Research & Development SuSE Linux S/390 and zSeries