[Bug target/54457] New: [x32] Fail to combine 64bit index + constant

[Bug target/54457] New: [x32] Fail to combine 64bit index + constant

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

             Bug #: 54457
           Summary: [x32] Fail to combine 64bit index + constant
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: hjl.tools@gmail.com
                CC: ubizjak@gmail.com


[hjl@gnu-ivb-1 pr54445]$ cat z.i
extern char array[40];

char
foo (long long int position) {
  return array[position + 1];
}
[hjl@gnu-ivb-1 pr54445]$
/export/build/gnu/gcc-x32/build-x86_64-linux/prev-gcc/xgcc
-B/export/build/gnu/gcc-x32/build-x86_64-linux/prev-gcc/ -Wall -O2 -std=gnu11
-mx32 -S z.i -da
[hjl@gnu-ivb-1 pr54445]$ cat z.s
    .file    "z.i"
    .text
    .p2align 4,,15
    .globl    foo
    .type    foo, @function
foo:
.LFB0:
    .cfi_startproc
    addq    $1, %rdi
    movzbl    array(%edi), %eax
    ret
    .cfi_endproc
.LFE0:
    .size    foo, .-foo
    .ident    "GCC: (GNU) 4.8.0 20120901 (experimental)"
    .section    .note.GNU-stack,"",@progbits
[hjl@gnu-ivb-1 pr54445]$ 

combine fails on:

Trying 6 -> 8:
Failed to match this instruction:
(set (reg:QI 66)
    (mem/j:QI (plus:SI (subreg:SI (plus:DI (reg/v:DI 62 [ position ])
                    (const_int 1 [0x1])) 0)
            (symbol_ref:SI ("array") [flags 0x40]  <var_decl 0x7ffff19ad260
arra
y>)) [0 array S1 A8]))

This should be a valid address.

[Bug target/54457] [x32] Fail to combine 64bit index + constant

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

--- Comment #1 from Uros Bizjak <ubizjak at gmail dot com> 2012-09-24 18:38:46 UTC ---
(In reply to comment #0)

> combine fails on:
> 
> Trying 6 -> 8:
> Failed to match this instruction:
> (set (reg:QI 66)
>     (mem/j:QI (plus:SI (subreg:SI (plus:DI (reg/v:DI 62 [ position ])
>                     (const_int 1 [0x1])) 0)
>             (symbol_ref:SI ("array") [flags 0x40]  <var_decl 0x7ffff19ad260
> arra
> y>)) [0 array S1 A8]))
> 
> This should be a valid address.

In principle yes, but the RTX is not accepted in ix86_decompose_address since
we have two displacements here. Combine should simplify this RTX to:

(set (reg:QI 68)
    (mem/j:QI (plus:SI (subreg:SI (reg/v:DI 62 [ position ]) 0)
            (const:SI (plus:SI (symbol_ref:SI ("array") [flags 0x40]  <var_decl
0x7f8d1bc41390 array>)
                    (const_int 1 [0x1])))) [0 array S1 A8]))


as is the case with -m32 (but rejected in ix86_address_subreg_operand):

  /* Don't allow SUBREGs that span more than a word.  It can lead to spill
     failures when the register is one word out of a two word structure.  */
  if (GET_MODE_SIZE (mode) > UNITS_PER_WORD)
    return false;

[Bug target/54457] [x32] Fail to combine 64bit index + constant

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

Uros Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2012-09-24
         AssignedTo|unassigned at gcc dot       |ubizjak at gmail dot com
                   |gnu.org                     |
     Ever Confirmed|0                           |1

--- Comment #2 from Uros Bizjak <ubizjak at gmail dot com> 2012-09-24 22:48:37 UTC ---
Created attachment 28261
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28261
Proposed patch

Patch that enhances combine_simplify_rtx to generate canonical binop sequences
that simplify_plus_minus can recognize and further optimize.

Bootstrapped and regression tested on x86_64-pc-linux-gnu.

Patched gcc generates expected code for the above testcase:

foo:
        movzbl  array+1(%edi), %eax
        ret

[Bug rtl-optimization/54457] [x32] Fail to combine 64bit index + constant

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

Uros Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|target                      |rtl-optimization
   Target Milestone|---                         |4.8.0

[Bug rtl-optimization/54457] [x32] Fail to combine 64bit index + constant

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

Uros Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #28261|0                           |1
        is obsolete|                            |

--- Comment #3 from Uros Bizjak <ubizjak at gmail dot com> 2012-09-25 00:00:51 UTC ---
Created attachment 28262
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28262
Updated patch

[Bug rtl-optimization/54457] [x32] Fail to combine 64bit index + constant

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

Uros Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |http://gcc.gnu.org/ml/gcc-p
                   |                            |atches/2012-09/msg01682.htm
                   |                            |l

--- Comment #4 from Uros Bizjak <ubizjak at gmail dot com> 2012-09-25 07:29:32 UTC ---
Patch at [1].

[1] http://gcc.gnu.org/ml/gcc-patches/2012-09/msg01682.html

[Bug rtl-optimization/54457] [x32] Fail to combine 64bit index + constant

[uros at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

--- Comment #5 from uros at gcc dot gnu.org 2012-10-01 15:00:50 UTC ---
Author: uros
Date: Mon Oct  1 15:00:41 2012
New Revision: 191928

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=191928
Log:
        PR rtl-optimization/54457
        * simplify-rtx.c (simplify_subreg):
    Simplify (subreg:M (op:N ((x:N) (y:N)), 0)
         to (op:M (subreg:M (x:N) 0) (subreg:M (x:N) 0)), where
    the outer subreg is effectively a truncation to the original mode M.

testsuite/ChangeLog:

        PR rtl-optimization/54457
        * gcc.target/i386/pr54457.c: New test.


Added:
    trunk/gcc/testsuite/gcc.target/i386/pr54457.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/simplify-rtx.c
    trunk/gcc/testsuite/ChangeLog

[Bug rtl-optimization/54457] [x32] Fail to combine 64bit index + constant

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

Uros Bizjak <ubizjak at gmail dot com> changed:

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

--- Comment #6 from Uros Bizjak <ubizjak at gmail dot com> 2012-10-02 13:31:34 UTC ---
Fixed.

[Bug rtl-optimization/54457] [x32] Fail to combine 64bit index + constant

[howarth at nitro dot med.uc.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

Jack Howarth <howarth at nitro dot med.uc.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |howarth at nitro dot
                   |                            |med.uc.edu

--- Comment #7 from Jack Howarth <howarth at nitro dot med.uc.edu> 2012-11-01 13:49:44 UTC ---
Shouldn't the gcc.target/i386/pr54457.c testcase be...

Index: gcc/testsuite/gcc.target/i386/pr54457.c
===================================================================
--- gcc/testsuite/gcc.target/i386/pr54457.c     (revision 193061)
+++ gcc/testsuite/gcc.target/i386/pr54457.c     (working copy)
@@ -1,4 +1,4 @@
-/* { dg-do compile { target { ! { ia32 } } } } */
+/* { dg-do compile { target { ! { ia32 || lp64 } } } } */
 /* { dg-options "-O2 -mx32 -maddress-mode=short" } */

 extern char array[40];

On x86_64-apple-darwin12 at -m64, the gcc.target/i386/pr54457.c testcase fails
the excessive errors test whereas the change above converts that to an
unsupported test.

[Bug rtl-optimization/54457] [x32] Fail to combine 64bit index + constant

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

--- Comment #8 from H.J. Lu <hjl.tools at gmail dot com> 2012-11-01 22:31:45 UTC ---
(In reply to comment #7)
> Shouldn't the gcc.target/i386/pr54457.c testcase be...
> 
> Index: gcc/testsuite/gcc.target/i386/pr54457.c
> ===================================================================
> --- gcc/testsuite/gcc.target/i386/pr54457.c     (revision 193061)
> +++ gcc/testsuite/gcc.target/i386/pr54457.c     (working copy)
> @@ -1,4 +1,4 @@
> -/* { dg-do compile { target { ! { ia32 } } } } */
> +/* { dg-do compile { target { ! { ia32 || lp64 } } } } */
>  /* { dg-options "-O2 -mx32 -maddress-mode=short" } */
> 
>  extern char array[40];
> 
> On x86_64-apple-darwin12 at -m64, the gcc.target/i386/pr54457.c testcase fails
> the excessive errors test whereas the change above converts that to an
> unsupported test.

It will disable test on Linux/x86-64.  We can add
check_effective_target_maybe_x32 to check if -mx32
works before compiling with -mx32.

[Bug rtl-optimization/54457] [x32] Fail to combine 64bit index + constant

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54457

--- Comment #9 from H.J. Lu <hjl.tools at gmail dot com> 2012-11-01 22:37:20 UTC ---
Like this:

# Return 1 if -mx32 can compile, 0 otherwise.

proc check_effective_target_maybe_x32 { } {
    return [check_no_compiler_messages maybe_x32 object {
        void foo (void) {}
    } {-mx32}]
}