[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

Michael Meissner  changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
 Resolution|--- |FIXED

--- Comment #13 from Michael Meissner  ---
Fixed with check-ins to trunk, and back-ports to gcc 6 and gcc 5.

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

--- Comment #12 from Michael Meissner  ---
Author: meissner
Date: Fri Mar 10 20:53:18 2017
New Revision: 246058

URL: https://gcc.gnu.org/viewcvs?rev=246058=gcc=rev
Log:
[gcc]
2017-03-10  Michael Meissner  

Back port from trunk
2017-03-01  Michael Meissner  

PR target/79439
* config/rs6000/predicates.md (current_file_function_operand): Do
not allow self calls to be local if the function is replaceable.

[gcc/testsuite]
2017-03-10  Michael Meissner  

Back port from trunk
2017-03-01  Michael Meissner  

PR target/79439
* gcc.target/powerpc/pr79439.c: New test.


Added:
branches/gcc-5-branch/gcc/testsuite/gcc.target/powerpc/pr79439.c
  - copied unchanged from r245930,
branches/gcc-6-branch/gcc/testsuite/gcc.target/powerpc/pr79439.c
Modified:
branches/gcc-5-branch/gcc/ChangeLog
branches/gcc-5-branch/gcc/config/rs6000/predicates.md
branches/gcc-5-branch/gcc/testsuite/ChangeLog

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

--- Comment #11 from Michael Meissner  ---
Author: meissner
Date: Mon Mar  6 22:47:03 2017
New Revision: 245930

URL: https://gcc.gnu.org/viewcvs?rev=245930=gcc=rev
Log:
[gcc]
2017-03-06  Michael Meissner  

Back port from trunk
2017-03-01  Michael Meissner  

PR target/79439
* config/rs6000/predicates.md (current_file_function_operand): Do
not allow self calls to be local if the function is replaceable.

[gcc/testsuite]
2017-03-06  Michael Meissner  

Back port from trunk
2017-03-01  Michael Meissner  

PR target/79439
* gcc.target/powerpc/pr79439.c: New test.



Added:
branches/gcc-6-branch/gcc/testsuite/gcc.target/powerpc/pr79439.c
  - copied, changed from r245813,
trunk/gcc/testsuite/gcc.target/powerpc/pr79439.c
Modified:
branches/gcc-6-branch/gcc/ChangeLog
branches/gcc-6-branch/gcc/config/rs6000/predicates.md
branches/gcc-6-branch/gcc/testsuite/ChangeLog

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

--- Comment #10 from Michael Meissner  ---
Author: meissner
Date: Wed Mar  1 18:33:21 2017
New Revision: 245813

URL: https://gcc.gnu.org/viewcvs?rev=245813=gcc=rev
Log:
[gcc]
2017-03-01  Michael Meissner  

PR target/79439
* config/rs6000/predicates.md (current_file_function_operand): Do
not allow self calls to be local if the function is replaceable.

[gcc/testsuite]
2017-03-01  Michael Meissner  

PR target/79439
* gcc.target/powerpc/pr79439.c: New test.


Added:
trunk/gcc/testsuite/gcc.target/powerpc/pr79439.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/config/rs6000/predicates.md
trunk/gcc/testsuite/ChangeLog

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

Michael Meissner  changed:

   What|Removed |Added

  Attachment #40851|0   |1
is obsolete||

--- Comment #9 from Michael Meissner  ---
Created attachment 40852
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40852=edit
Potential patch to check if self calls are replaceable #2

I deleted a comment by mistake in the first patch.

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

Michael Meissner  changed:

   What|Removed |Added

 Status|NEW |ASSIGNED
   Assignee|unassigned at gcc dot gnu.org  |meissner at gcc dot 
gnu.org

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[meissner at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

Michael Meissner  changed:

   What|Removed |Added

 CC||meissner at gcc dot gnu.org

--- Comment #8 from Michael Meissner  ---
Created attachment 40851
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40851=edit
Potential patch to check if self calls are replaceable.

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

Alexander Monakov  changed:

   What|Removed |Added

 CC||amonakov at gcc dot gnu.org

--- Comment #7 from Alexander Monakov  ---
Note that there's also a bug in the middle-end since gcc makes an assumption
that such calls are always self-recursive on any target; see comments 6-9 in
bug 56727.

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

--- Comment #6 from Jakub Jelinek  ---
(In reply to David Edelsohn from comment #5)
> current_file_function_operand probably needs to add a test for
> flag_semantic_interposition when the ABI mandates interpolation.

Maybe better just call decl_replaceable_p (current_function_decl) if not
SYMBOL_REF_LOCAL_P (or something similar).

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[dje at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

--- Comment #5 from David Edelsohn  ---
current_file_function_operand probably needs to add a test for
flag_semantic_interposition when the ABI mandates interpolation.

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

Segher Boessenkool  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2017-02-09
 Ever confirmed|0   |1

--- Comment #4 from Segher Boessenkool  ---
We have (in rs6000/predicates.md):

;; Return 1 if the operand is a SYMBOL_REF for a function known to be in
;; this file.
(define_predicate "current_file_function_operand"
  (and (match_code "symbol_ref")
   (match_test "(DEFAULT_ABI != ABI_AIX || SYMBOL_REF_FUNCTION_P (op))
&& (SYMBOL_REF_LOCAL_P (op)
|| op == XEXP (DECL_RTL (current_function_decl), 0))
&& !((DEFAULT_ABI == ABI_AIX
  || DEFAULT_ABI == ABI_ELFv2)
 && (SYMBOL_REF_EXTERNAL_P (op)
 || SYMBOL_REF_WEAK (op)))")))

so this seems to be on purpose.

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

--- Comment #3 from Segher Boessenkool  ---
-fpic does the trick.  Confirmed.

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[fw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

--- Comment #2 from Florian Weimer  ---
(In reply to Segher Boessenkool from comment #1)
> What command line options does this need?

Sorry, I used -O2 -fpic.

Indeed, GCC seems to perform target-independent optimizations based on an
assumption that the recursive call calls the same function as defined in the
translation unit.  If this is the desired behavior, the proper fix would be to
use a local reference for the recursive call.  This would make those
optimizations consistent, and interposition would work to some extent.  Of
course, the recursive calls wouldn't be interposed anymore, but the TOC
corruption would at least be gone.

[Bug target/79439] Missing nop instruction after recursive call corrupts TOC register

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79439

--- Comment #1 from Segher Boessenkool  ---
What command line options does this need?  I get different assembly
(also with GCC 6), since GCC recognises that rec can never return:

.globl rec
.type   rec, @function
rec:
.LCF1:
0:  addis 2,12,.TOC.-.LCF1@ha
addi 2,2,.TOC.-.LCF1@l
.localentry rec,.-rec
mflr 0
std 31,-8(1)
mr 31,3
std 0,16(1)
stdu 1,-48(1)
.p2align 4,,15
.L3:
bl f
nop
cmpdi 7,3,0
beq 7,.L3
addi 3,31,1
extsw 3,3
bl rec
.long 0
.byte 0,0,0,1,128,1,0,0