[Bug target/60617] [4.8 Regression] unable to find a register to spill in class 'LO_REGS'

[Bug target/60617] [4.8 Regression] unable to find a register to spill in class 'LO_REGS'

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60617

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.8.3

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
-fno-tree-dce is certainly not a good idea ... (doesn't make it a non-bug, of
course).

[Bug target/60617] [4.8 Regression] unable to find a register to spill in class 'LO_REGS'

[venkataramanan.kumar at amd dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60617

Venkataramanan <venkataramanan.kumar at amd dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |venkataramanan.kumar at amd dot co
                   |                            |m

--- Comment #2 from Venkataramanan <venkataramanan.kumar at amd dot com> ---
This bug occurrs with GCC trunk as well with IRA and reload. 
Can be reproduced with -std=c++11 -fno-tree-dce -fno-omit-frame-pointer -O2
-mno-lra.

[Bug target/60617] [4.8 Regression] unable to find a register to spill in class 'LO_REGS'

[venkataramanan.kumar at amd dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60617

--- Comment #3 from Venkataramanan <venkataramanan.kumar at amd dot com> ---
The bug is now hidden in trunk by revision 209897

The patch "Remove PUSH_ARGS_REVERSED from the RTL expander"
(reference below) seems to change the way arguments are handled in RTL. 

Ref:
http://gcc.gnu.org/git/?p=gcc.git;a=commit;h=bf29c577b9128551d76adc5b0331d375be49d7d3

[Bug target/60617] [4.8 Regression] unable to find a register to spill in class 'LO_REGS'

[venkataramanan.kumar at amd dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60617

--- Comment #4 from Venkataramanan <venkataramanan.kumar at amd dot com> ---
Reverting this patch in 209897 bug still occurs in trunk with -mno-lra.

SPILL failure occurs for regno 110 ("dst" operand) in below instruction 

(insn 634 633 635 27 (parallel [
            (set (reg:SI 3 r3)
                (ior:SI (eq:SI (reg/v:SI 110 [ dst ]) <== This operand r5 is
registers gets assigned
                        (reg/v:SI 112 [ op2 ]))
                    (eq:SI (reg/v:SI 110 [ dst ]) <== This operand
                        (reg/v:SI 111 [ op1 ]))))
            (clobber (reg:CC 100 cc))
        ]) ../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:179 300
{*ior_scc_scc

First observation is that reload is not able to reuse "r5" that was used in
second reload in operation for the same register id 110 "dst"


The IRA Dump shows.

(insn 632 631 633 27 (set (reg:SI 1 r1)
        (reg/v:SI 110 [ dst ]))
../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:179 667 {*thumb2_movsi_vfp}
     (nil))
(insn 633 632 634 27 (set (reg:SI 2 r2)
        (const_int 0 [0]))
../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:179 667 {*thumb2_movsi_vfp}
     (nil))
(insn 634 633 635 27 (parallel [
            (set (reg:SI 3 r3)
                (ior:SI (eq:SI (reg/v:SI 110 [ dst ])
                        (reg/v:SI 112 [ op2 ]))
                    (eq:SI (reg/v:SI 110 [ dst ])
                        (reg/v:SI 111 [ op1 ]))))
            (clobber (reg:CC 100 cc))
        ]) ../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:179 300
{*ior_scc_scc}

The register operand 110 "dst" is already passed as argument 1 and hence gets
register r1. See insn 632.

But this is not reused by  insn 634.

However there are some other places in IRA dump where the same expression
occurs and there register r1 is used. Here operand "dst" 110 is marked as dead.


(insn 431 430 433 24 (set (reg:SI 1 r1)
        (reg/v:SI 110 [ dst ]))
../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:388 667 {*thumb2_movsi_vfp}
     (expr_list:REG_DEAD (reg/v:SI 110 [ dst ])
        (nil)))

(insn 433 431 432 24 (parallel [
            (set (reg:SI 3 r3)
                (ior:SI (eq:SI (reg/v:SI 112 [ op ])
                        (reg:SI 1 r1))
                    (eq:SI (reg/v:SI 111 [ op ])
                        (reg:SI 1 r1))))
            (clobber (reg:CC 100 cc))
        ]) ../Source/JavaScriptCore/jit/JITArithmetic32_64.cpp:388 300
{*ior_scc_scc 


Still working on why IRA is not replacing the operand with R1 here, but
replaces in other places.

[Bug target/60617] [4.8 Regression] unable to find a register to spill in class 'LO_REGS'

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60617

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.3                       |4.8.4

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 4.8.3 is being released, adjusting target milestone.

[Bug target/60617] [4.8 Regression] unable to find a register to spill in class 'LO_REGS'

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60617

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ra
             Target|                            |arm
           Priority|P3                          |P2

[Bug target/60617] [4.8 Regression] unable to find a register to spill in class 'LO_REGS'

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60617

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.4                       |4.8.5

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.8.4 has been released.

[Bug target/60617] [4.8 Regression] unable to find a register to spill in class 'LO_REGS'

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60617

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|4.8.5                       |4.9.0
      Known to fail|                            |4.8.5

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed for 4.9.0.