Don't include glibc symbol versions in libgcc.

+

+# Override t-slibgcc-elf-ver to export some libgcc symbols with

+# the symbol versions that glibc used.

+SHLIB_MAPFILES += $(srcdir)/config/libgcc-glibc.ver

+#SHLIB_MAPFILES += $(srcdir)/config/libgcc-glibc.ver

+

+# Use unwind-dw2-fde

+LIB2ADDEH = $(srcdir)/unwind-dw2.c $(srcdir)/unwind-dw2-fde.c \

http://www.linux-mips.org/archives/linux-mips/2004-09/msg00000.html

Atsushi Nemoto <anemo@mba.ocn.ne.jp> writes:

>/ Is this a get_user's problem or gcc's?/

The latter.  gcc is putting the empty asm:

        __asm__ ("":"=r" (__gu_val));

into the delay slot of the call.

Part of the problem is that gcc estimates the length of an asm to be the

number of instruction separators + 1.  This means that it estimates the

asm above to be one instruction long, which is perhaps a little silly

for an empty string.

But the real problem is that gcc should never trust this estimate anyway,

since each "instruction" could obviously be a multi-instruction macro.

gcc should certainly never put asms into delay slots.

FWIW, I don't think the bug is specific to 3.3 or 3.4.  It could

probably trigger for other gcc versions too.  It is highly dependent

on scheduling though.

The attached 3.4.x patch fixes the problem there, but if you want to work

around it for old versions, just avoid using empty asms if you can,

or make them volatile if you can't.

Of course, the problem isn't confined to empty asms.  If you have an asm

with a single, multi-instruction macro, gcc might try putting that in a

delay slot too.  You should at least get an assembler warning in that case.

Richard

--- gcc-3.4.1/gcc/config/mips/mips.md-orig	2004-09-02 10:38:36.000000000 -0500

+++ gcc-3.4.1/gcc/config/mips/mips.md	2004-09-02 10:38:42.000000000 -0500

@@ -251,7 +251,7 @@

 ;; Can the instruction be put into a delay slot?

 (define_attr "can_delay" "no,yes"

-  (if_then_else (and (eq_attr "type" "!branch,call,jump")

+  (if_then_else (and (eq_attr "type" "!branch,call,jump,multi")

 		     (and (eq_attr "hazard" "none")

 			  (eq_attr "single_insn" "yes")))

 		(const_string "yes")

[committed] Fix target/17565: asms in delay slots

    * From: Richard Sandiford <rsandifo at redhat dot com>

    * To: gcc-patches at gcc dot gnu dot org

    * Date: Mon, 20 Sep 2004 07:55:58 +0100

    * Subject: [committed] Fix target/17565: asms in delay slots

The MIPS port was allowing asms to be put into delay slots if the

compiler guesses they are only one instruction long.  This is wrong

because of the possibility of it containing macros.

The problem can be reproduced as an assembler warning

in the following testcase:

int foo (int n)

{

  register int k asm ("$16") = n;

  if (k > 0)

    {

      bar ();

      asm ("li %0,0x12345678" : "=r" (k));

    }

  return k;

}

because the multi-instruction asm statement goes into the delay

slot of the call to bar().

This is reduced from a much more serious linux problem.  Linux is fond

of using empty asm statements, and since gcc estimates empty asms to be

one instruction long, they too might be put into delay slots.  This

actually has the effect of putting the following instruction into the

delay slot instead.  Since there's no assembler warning, the problem was

only detected as a run-time failure.

The fix is simple: set the asm value of "can_delay" to "no".

Tested on mipsisa64-elf, applied to mainline.

This problem goes back to at least 2.95, so it isn't technically a

regression.  On the other hand, it's the kind of bug that could trigger

for different types of code in different releases, so I'm sure there's

a testcase that fails (say) in 3.4 and not in 2.95.  Will probably ask

Mark for permission to backport to 3.4.

Richard

	PR target/17565

	* config/mips/mips.md (define_asm_attributes): Set can_delay to no.

testsuite/

	* gcc.target/mips/asm-1.c: New test.

Index: config/mips/mips.md

===================================================================

RCS file: /cvs/gcc/gcc/gcc/config/mips/mips.md,v

retrieving revision 1.306

diff -c -p -F^\([(a-zA-Z0-9_]\|#define\) -r1.306 mips.md

*** gcc/gcc/config/mips/mips.md	13 Sep 2004 19:32:05 -0000	1.306

--- gcc/gcc/config/mips/mips.md	20 Sep 2004 06:52:31 -0000

*************** (define_attr "may_clobber_hilo" "no,yes"

*** 266,272 ****

  ;; Describe a user's asm statement.

  (define_asm_attributes

!   [(set_attr "type" "multi")])

  ;; .........................

  ;;

--- 266,273 ----

  ;; Describe a user's asm statement.

  (define_asm_attributes

!   [(set_attr "type" "multi")

!    (set_attr "can_delay" "no")])

  ;; .........................

  ;;

Index: testsuite/gcc.target/mips/asm-1.c

===================================================================

RCS file: testsuite/gcc.target/mips/asm-1.c

diff -N testsuite/gcc.target/mips/asm-1.c

*** gcc/gcc/testsuite/gcc.target/mips/asm-1.c	1 Jan 1970 00:00:00 -0000

--- gcc/gcc/testsuite/gcc.target/mips/asm-1.c	20 Sep 2004 06:52:31 -0000

***************

*** 0 ****

--- 1,14 ----

+ /* PR target/17565.  GCC used to put the asm into the delay slot

+    of the call.  */

+ /* { dg-do assemble } */

+ /* { dg-options "-O" } */

+ int foo (int n)

+ {

+   register int k asm ("$16") = n;

+   if (k > 0)

+     {

+       bar ();

+       asm ("li %0,0x12345678" : "=r" (k));

+     }

+   return k;

+ }

revision 1.12

date: 2004/07/16 15:13:40;  author: segher;  state: Exp;  lines: +1 -1

        * config/rs6000/eabi.asm (__eabi_convert): Fix typo (cmpi vs. cmpwi).

Index: gcc/config/rs6000/eabi.asm

===================================================================

RCS file: /cvs/gcc/gcc/gcc/config/rs6000/eabi.asm,v

retrieving revision 1.11

retrieving revision 1.12

diff -u -b -B -w -p -r1.11 -r1.12

--- gcc/gcc/config/rs6000/eabi.asm	20 Sep 2002 23:46:58 -0000	1.11

+++ gcc/gcc/config/rs6000/eabi.asm	16 Jul 2004 15:13:40 -0000	1.12

@@ -252,7 +252,7 @@ FUNC_START(__eabi_convert)

 .Lcvt:

 	lwzu	6,4(3)				/* pointer to convert */

-	cmpi	0,6,0

+	cmpwi	0,6,0

 	beq-	.Lcvt2				/* if pointer is null, don't convert */

         add	6,6,12				/* convert pointer */