[Bug lto/78529] New: gcc.c-torture/execute/builtins/strcat-chk.c failed with lto/O2

[amker at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78529

            Bug ID: 78529
           Summary: gcc.c-torture/execute/builtins/strcat-chk.c failed
                    with lto/O2
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amker at gcc dot gnu.org
  Target Milestone: ---

Hi,
With below commit:
commit c618308c1b2a474bd56ede831f681a49f4327d4c
Author: prathamesh3492 <prathamesh3492@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Wed Nov 23 10:52:25 2016 +0000

    2016-11-23  Richard Biener  <rguenther@suse.de>
            Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.rog>

        PR tree-optimization/78154
        * tree-vrp.c (gimple_stmt_nonzero_warnv_p): Return true if function
        returns it's argument and the argument is nonnull.
        * builtin-attrs.def: Define ATTR_RETURNS_NONNULL,
        ATT_RETNONNULL_NOTHROW_LEAF.
        * builtins.def (BUILT_IN_MEMPCPY): Change attribute to
        ATTR_RETNONNULL_NOTHROW_LEAF.
        (BUILT_IN_STPCPY): Likewise.
        (BUILT_IN_STPNCPY): Likewise.
        (BUILT_IN_MEMPCPY_CHK): Likewise.
        (BUILT_IN_STPCPY_CHK): Likewise.
        (BUILT_IN_STPNCPY_CHK): Likewise.
        (BUILT_IN_STRCAT): Change attribute to ATTR_RET1_NOTHROW_NONNULL_LEAF.
        (BUILT_IN_STRNCAT): Likewise.
        (BUILT_IN_STRNCPY): Likewise.
        (BUILT_IN_MEMSET_CHK): Likewise.
        (BUILT_IN_STRCAT_CHK): Likewise.
        (BUILT_IN_STRCPY_CHK): Likewise.
        (BUILT_IN_STRNCAT_CHK): Likewise.
        (BUILT_IN_STRNCPY_CHK): Likewise.

    testsuite/
        * gcc.dg/tree-ssa/pr78154.c: New test.


    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@242745
138bc75d-0d04-0410-961f-82ee72b054a4

We have new failure:
FAIL: gcc.c-torture/execute/builtins/strcat-chk.c execution, -O2 -flto
-fuse-linker-plugin -fno-fat-lto-objects 

With/without the revision, there is difference in assembly like:
*** 1368,1387 ****
    4023e4:     b9401261        ldr     w1, [x19, #16]
    4023e8:     6b00003f        cmp     w1, w0
    4023ec:     54ffff01        b.ne    4023cc <test1+0x14c>  // b.any
!   4023f0:     91001664        add     x4, x19, #0x5
!   4023f4:     d2800802        mov     x2, #0x40                       // #64
!   4023f8:     52800b01        mov     w1, #0x58                       // #88
    4023fc:     aa1303e0        mov     x0, x19
    402400:     94000950        bl      404940 <memset>
    402404:     b9400a96        ldr     w22, [x20, #8]
    402408:     f9400297        ldr     x23, [x20]
    40240c:     d2800762        mov     x2, #0x3b                       // #59
    402410:     10071c81        adr     x1, 4107a0 <s1+0x90>
!   402414:     aa0403e0        mov     x0, x4
    402418:     f90023b7        str     x23, [x29, #64]
    40241c:     b9004bb6        str     w22, [x29, #72]
    402420:     97fffc0c        bl      401450 <__strcat_chk>
!   402424:     eb00001f        cmp     x0, x0
    402428:     54fffd21        b.ne    4023cc <test1+0x14c>  // b.any
    40242c:     10071820        adr     x0, 410730 <s1+0x20>
    402430:     f94023a2        ldr     x2, [x29, #64]
--- 1368,1387 ----
    4023e4:     b9401261        ldr     w1, [x19, #16]
    4023e8:     6b00003f        cmp     w1, w0
    4023ec:     54ffff01        b.ne    4023cc <test1+0x14c>  // b.any
!   4023f0:     d2800802        mov     x2, #0x40                       // #64
!   4023f4:     52800b01        mov     w1, #0x58                       // #88
!   4023f8:     91001678        add     x24, x19, #0x5
    4023fc:     aa1303e0        mov     x0, x19
    402400:     94000950        bl      404940 <memset>
    402404:     b9400a96        ldr     w22, [x20, #8]
    402408:     f9400297        ldr     x23, [x20]
    40240c:     d2800762        mov     x2, #0x3b                       // #59
    402410:     10071c81        adr     x1, 4107a0 <s1+0x90>
!   402414:     aa1803e0        mov     x0, x24
    402418:     f90023b7        str     x23, [x29, #64]
    40241c:     b9004bb6        str     w22, [x29, #72]
    402420:     97fffc0c        bl      401450 <__strcat_chk>
!   402424:     eb00031f        cmp     x24, x0
    402428:     54fffd21        b.ne    4023cc <test1+0x14c>  // b.any
    40242c:     10071820        adr     x0, 410730 <s1+0x20>
    402430:     f94023a2        ldr     x2, [x29, #64]


Looks like the "cmp x0, x0" instruction is wrongly optimized?

GCC is configured as:

configure --target=aarch64-none-elf --prefix=... --with-gmp=... --with-mpfr=...
--with-mpc=... --with-isl=... --with-pkgversion=unknown --disable-shared
--disable-nls --disable-threads --disable-tls --enable-checking=yes
--enable-languages=c,c++,fortran --with-newlib