[Bug tree-optimization/83543] New: strlen of a local array member not optimized on some targets

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83543

            Bug ID: 83543
           Summary: strlen of a local array member not optimized on some
                    targets
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

Bug 83462 reports (among others) a failure in the new
c-c++-common/Warray-bounds-4.c test on powerpc64le.  The failure is due to a
strlen optimization that's for some reason not working on this target (and on
some others, including arm-none-eabi) but that works fine on x86_64-linux.  The
test case below shows the difference in cross-compiler output between these
three architectures.

$ (set -x && cat z.c && for arch in '' arm-none-eabi powerpc64le-linux; do
/ssd/build/$arch/gcc-git/gcc/xgcc -B /ssd/build/$arch/gcc-git/gcc -O2 -S -Wall
-fdump-tree-optimized=/dev/stdout z.c; done)
+ cat z.c
struct S { char a[7]; };

void f (void)
{
  struct S s = { "12345" };
  if (__builtin_strlen (s.a) != 5)
    __builtin_abort ();
}
+ for arch in ''\'''\''' arm-none-eabi powerpc64le-linux
+ /ssd/build//gcc-git/gcc/xgcc -B /ssd/build//gcc-git/gcc -O2 -S -Wall
-fdump-tree-optimized=/dev/stdout z.c

;; Function f (f, funcdef_no=0, decl_uid=1894, cgraph_uid=0, symbol_order=0)

f ()
{
  <bb 2> [local count: 1073741825]:
  return;

}


+ for arch in ''\'''\''' arm-none-eabi powerpc64le-linux
+ /ssd/build/arm-none-eabi/gcc-git/gcc/xgcc -B
/ssd/build/arm-none-eabi/gcc-git/gcc -O2 -S -Wall
-fdump-tree-optimized=/dev/stdout z.c

;; Function f (f, funcdef_no=0, decl_uid=4155, cgraph_uid=0, symbol_order=0)

f ()
{
  struct S s;
  unsigned int _1;

  <bb 2> [local count: 1073741825]:
  s = *.LC0;
  _1 = __builtin_strlen (&s.a);
  if (_1 != 5)
    goto <bb 3>; [0.00%]
  else
    goto <bb 4>; [99.96%]

  <bb 3> [count: 0]:
  __builtin_abort ();

  <bb 4> [local count: 1073312327]:
  s ={v} {CLOBBER};
  return;

}


+ for arch in ''\'''\''' arm-none-eabi powerpc64le-linux
+ /ssd/build/powerpc64le-linux/gcc-git/gcc/xgcc -B
/ssd/build/powerpc64le-linux/gcc-git/gcc -O2 -S -Wall
-fdump-tree-optimized=/dev/stdout z.c

;; Function f (f, funcdef_no=0, decl_uid=2784, cgraph_uid=0, symbol_order=0)

f ()
{
  struct S s;
  long unsigned int _1;

  <bb 2> [local count: 1073741825]:
  s = *.LC0;
  _1 = __builtin_strlen (&s.a);
  if (_1 != 5)
    goto <bb 3>; [0.00%]
  else
    goto <bb 4>; [99.96%]

  <bb 3> [count: 0]:
  __builtin_abort ();

  <bb 4> [local count: 1073312327]:
  s ={v} {CLOBBER};
  return;

}