[Bug target/51931] New: No support for MIPS16 long branches

[Bug target/51931] New: No support for MIPS16 long branches

[rsandifo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51931

             Bug #: 51931
           Summary: No support for MIPS16 long branches
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rsandifo@gcc.gnu.org


The MIPS port doesn't detect when MIPS16 branches are out of range,
and it doesn't provide the same kind of "branch around jump" fallback
as it does for non-MIPS16 code.

This has always been a problem, and shows up as a long-standing failure
in gcc.c-torture/compile/20001226-1.c and g++.dg/opt/longbranch1.C.
I've thought about various fixes, such as saving a MIPS16 register
to $1 before using it as a scratch, then restoring it in the branch
delay slot.  But there are various ugly cases.

The bug only triggers for very large functions and at least these days
there's a workaround: add __attribute__((nomips16)).

[Bug target/51931] No support for MIPS16 long branches

[rsandifo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51931

--- Comment #1 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> 2012-01-22 10:33:10 UTC ---
Author: rsandifo
Date: Sun Jan 22 10:33:07 2012
New Revision: 183389

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=183389
Log:
gcc/testsuite/
    PR target/51931
    * gcc.c-torture/compile/20001226-1.c: Add nomips16 attribute.
    * g++.dg/opt/longbranch1.C: Likewise.

Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/opt/longbranch1.C
    trunk/gcc/testsuite/gcc.c-torture/compile/20001226-1.c

[Bug target/51931] No support for MIPS16 long branches

[rsandifo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51931

rsandifo@gcc.gnu.org <rsandifo at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-01-22
     Ever Confirmed|0                           |1

[Bug target/51931] No support for MIPS16 long branches

[rsandifo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51931

--- Comment #2 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> 2012-08-02 21:32:02 UTC ---
Author: rsandifo
Date: Thu Aug  2 21:31:57 2012
New Revision: 190104

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=190104
Log:
gcc/
    PR target/51931
    * config/mips/mips-protos.h (mips_strip_unspec_address): Declare.
    * config/mips/mips.c (mips_strip_unspec_address): Make extern.
    (mips16_rewrite_pool_constant): Make a copy of the pool constant
    before adding to a PC-relative table.
    (mips16_lay_out_constants): Add a SPLIT_P parameter.
    (mips16_load_branch_target, mips16_split_long_branches): New functions.
    (mips_reorg): Update call to mips16_lay_out_constants.
    Call mips16_split_long_branches.
    * config/mips/predicates.md (pc_or_label_operand): Delete.
    * config/mips/mips.md (length): Add a calculation for MIPS16 branches.
    Move the extended_mips16 handling further down.
    (*branch_equality<mode>_mips16): Replace use pc_or_label_operand
    with explicit label_ref and pc.  Follow the usual operand numbering.
    (*branch_equality<mode>_mips16_inverted): New pattern.
    (*jump_mips16): Add length attribute.
    (indirect_jump_and_restore_<mode>): New pattern.
    (consttable_int): Call mips_strip_unspec_address on the operand.

gcc/testsuite/
    PR target/51931
    * gcc.c-torture/compile/20001226-1.c: Remove nomips16 attribute.
    * g++.dg/opt/longbranch1.C: Likewise.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/mips/mips-protos.h
    trunk/gcc/config/mips/mips.c
    trunk/gcc/config/mips/mips.md
    trunk/gcc/config/mips/predicates.md
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/opt/longbranch1.C
    trunk/gcc/testsuite/gcc.c-torture/compile/20001226-1.c

[Bug target/51931] No support for MIPS16 long branches

[rsandifo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51931

rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> ---
Fix some time ago.