[Bug inline-asm/28686] ebp from clobber list used as operand

[spark at gcc dot gnu dot org]

--- Comment #8 from spark at gcc dot gnu dot org  2007-03-13 23:43 ---
I believe all issues are fixed at this point,
except for the extra error message of can't find a register.
But since it's accompanied with a proper error message,
I don't think this is a problem anymore.

$gcc -fPIC -fomit-frame-pointer -O2 -S t.c  grep DEBUG t.s
#DEBUG %0=(%esp), clobber: %ebp, ...
$gcc -DNBEFORE=1 -fPIC -fomit-frame-pointer -O2 -S t.c  grep DEBUG t.s
#DEBUG %0=(%esp), clobber: %ebp, ...
$gcc-O1 -S t.c $@  grep DEBUG t.s
t.c: In function 'test_function':
t.c:15: error: can't find a register in class 'GENERAL_REGS' while reloading
'asm'
t.c:15: error: 'asm' operand has impossible constraints
$gcc   -O1 -fPIC -S t.c $@  grep DEBUG t.s
t.c: In function 'test_function':
t.c:20: error: bp cannot be used in asm here
t.c:15: error: can't find a register in class 'GENERAL_REGS' while reloading
'asm'
t.c:15: error: 'asm' operand has impossible constraints
$gcc -fPIC  -O0 -S t.c  grep DEBUG t.s
t.c: In function 'test_function':
t.c:20: error: bp cannot be used in asm here
$gcc -fPIC  -O0 -S t.c -fomit-frame-pointer  grep DEBUG
t.s
#DEBUG %0=12(%esp), clobber: %ebp, ...


-- 

spark at gcc dot gnu dot org changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
 Resolution||FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28686

[Bug inline-asm/28686] ebp from clobber list used as operand

[spark at gcc dot gnu dot org]

--- Comment #7 from spark at gcc dot gnu dot org  2007-02-06 19:43 ---
Subject: Bug 28686

Author: spark
Date: Tue Feb  6 19:43:41 2007
New Revision: 121663

URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=121663
Log:
2007-02-06  Seongbae Park [EMAIL PROTECTED]

PR inline-asm/28686
* global.c (compute_regsets): New function.
(global_alloc): Refactored ELIMINABLE_REGSET
and NO_GLOBAL_ALLOC_REGS computation out.
(rest_of_handle_global_alloc): Call compute_regsets()
for non-optimizing case.


Modified:
trunk/gcc/ChangeLog
trunk/gcc/global.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28686

[Bug inline-asm/28686] ebp from clobber list used as operand

[spark at gcc dot gnu dot org]

--- Comment #5 from spark at gcc dot gnu dot org  2007-02-01 17:47 ---
-O1 error problem is due to constant assignment of var.
If you replace:
  long var = 42; 
with something like:
  long var = func();

It compiles without an error (though it still has the #3 problem
of using %ebp even though it's marked clobbered).

This is a corner case for reload, because it knows the register contains a
constant, and thinks there will be at least some scratch register to load it
to. Unfortunately, due to the problematic asm statement having clobbers for all
registers (except %ebp, but %ebp is not available for general allocation
without -fomit-frame-pointer) there's no register available to load the
constant to.

So, the workaround for this problem is to have a local variable that's not
initialized from a constant.

So I'm deferring this #2 problem, and will take a look at #3 now.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28686

[Bug inline-asm/28686] ebp from clobber list used as operand

[spark at gcc dot gnu dot org]

--- Comment #6 from spark at gcc dot gnu dot org  2007-02-01 23:15 ---
Subject: Bug 28686

Author: spark
Date: Thu Feb  1 23:15:13 2007
New Revision: 121477

URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=121477
Log:
2007-2-01   Seongbae Park [EMAIL PROTECTED]

PR inline-asm/28686
* global.c (global_alloc): Add mising initialization of
ELIMINABLE_REGSET.

2007-02-01  Roger Sayle  [EMAIL PROTECTED]



Modified:
trunk/gcc/ChangeLog
trunk/gcc/global.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28686

[Bug inline-asm/28686] ebp from clobber list used as operand

[ian at airs dot com]

-- 

ian at airs dot com changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
 Ever Confirmed|0   |1
   Last reconfirmed|-00-00 00:00:00 |2007-01-30 19:09:28
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28686

[Bug inline-asm/28686] ebp from clobber list used as operand

[michael dot meissner at amd dot com]

--- Comment #3 from michael dot meissner at amd dot com  2007-01-30 20:17 
---
Created an attachment (id=12982)
 -- (http://gcc.gnu.org/bugzilla/attachment.cgi?id=12982action=view)
Secondary error

Note, this is 32-bit only.  If you compile epb2.c with -fpic -m32 and no
optimization, it generates incorrect code, in that at -O0 it does not omit the
frame pointer, but the asm is claimed to clobber %ebp, and subsequent local
variables will use %ebp.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28686

[Bug inline-asm/28686] ebp from clobber list used as operand

[spark at gcc dot gnu dot org]

-- 

spark at gcc dot gnu dot org changed:

   What|Removed |Added

 CC|seongbae dot park at gmail  |
   |dot com |
 AssignedTo|unassigned at gcc dot gnu   |spark at gcc dot gnu dot org
   |dot org |
 Status|NEW |ASSIGNED
   Last reconfirmed|2007-01-30 19:09:28 |2007-01-30 21:43:48
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28686

[Bug inline-asm/28686] ebp from clobber list used as operand

[spark at gcc dot gnu dot org]

--- Comment #4 from spark at gcc dot gnu dot org  2007-01-31 00:28 ---
Looks like eliminable_regset is not cleared per every invocation of
global_alloc, making stale bits from the compilation of previous function hang
around - hence a presence of a previous function makes difference. 
Following patch seems to fix -O2 problem.
I'm now on to -O1 and -O0 issues.

Index: global.c
===
--- global.c(revision 121353)
+++ global.c(working copy)
@@ -354,6 +354,7 @@ global_alloc (void)
  are safe to use only within a basic block.  */

   CLEAR_HARD_REG_SET (no_global_alloc_regs);
+  CLEAR_HARD_REG_SET (eliminable_regset);

   /* Build the regset of all eliminable registers and show we can't use those
  that we already know won't be eliminated.  */
@@ -2548,4 +2549,3 @@ struct tree_opt_pass pass_global_alloc =
   TODO_ggc_collect, /* todo_flags_finish */
   'g'   /* letter */
 };
-


-- 

spark at gcc dot gnu dot org changed:

   What|Removed |Added

 CC||spark at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28686

[Bug inline-asm/28686] ebp from clobber list used as operand

[Martin dot vGagern at gmx dot net]

--- Comment #2 from Martin dot vGagern at gmx dot net  2007-01-25 11:06 
---
As this has been unconfirmed for so long and should be relatively easy to
confirm, here are the commands to reproduce the problems above:

gcc -fPIC -fomit-frame-pointer -O2 -S ebp.c  grep DEBUG ebp.s
gcc-O1 -S ebp.c  grep DEBUG ebp.s
gcc -fPIC  -O0 -S ebp.c  grep DEBUG ebp.s

In case you want to reproduce all the combinations given in the table at the
end of my source file, you can use this bash loop:

for ((i=0; i  32; ++i)); do
  ARGS=-O$((i%4)); 
  ARGS=$( [[ $((i4)) -eq 0 ]] || echo -fomit-frame-pointer )$ARGS;
  ARGS=$( [[ $((i8)) -eq 0 ]] || echo -fPIC )$ARGS;
  ARGS=$( [[ $((i16)) -eq 0 ]] || echo -DNBEFORE )$ARGS;
  echo -- $ARGS --;
  gcc $ARGS -S ebp.c  grep DEBUG ebp.s
done

It might be you can reproduce this behaviour, but are not certain it is a bug.
I can understand you might doubt a single of my three mentioned problems, but
do you really believe they are all three as things should be? If in doubt,
perhaps best concentrate on problem 1, ebp being clobbered and still used.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28686

[Bug inline-asm/28686] ebp from clobber list used as operand

[Martin dot vGagern at gmx dot net]

--- Comment #1 from Martin dot vGagern at gmx dot net  2006-08-10 19:49 
---
Created an attachment (id=12058)
 -- (http://gcc.gnu.org/bugzilla/attachment.cgi?id=12058action=view)
Test case including compilation result table

This is the above test case, and appended is a table matching compiler flags to
error messages or register allocation information.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28686