[Bug target/57536] New: Inconsistent behavior of strlen inline and unroll

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57536

            Bug ID: 57536
           Summary: Inconsistent behavior of strlen inline and unroll
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
                CC: uros at gcc dot gnu.org
            Target: i386

There is

  /* X86_TUNE_UNROLL_STRLEN */
  m_486 | m_PENT | m_PPRO | m_ATOM | m_CORE_ALL | m_K6 | m_AMD_MULTIPLE |
m_GENERIC,

ix86_expand_strlen has

  if (TARGET_UNROLL_STRLEN && eoschar == const0_rtx && optimize > 1
      && !TARGET_INLINE_ALL_STRINGOPS
      && !optimize_insn_for_size_p ()
      && (!CONST_INT_P (align) || INTVAL (align) < 4)) 
    return false;

The decision depends on both TARGET_UNROLL_STRLEN and
TARGET_INLINE_ALL_STRINGOPS.  If both TARGET_UNROLL_STRLEN
and TARGET_INLINE_ALL_STRINGOPS are false, strlen is
inlined:

[hjl@gnu-6 gcc]$ cat x.i
int strlen (const char *);

int
foo (const char *s)
{
  return strlen (s);
}
[hjl@gnu-6 gcc]$ gcc -S -m32 -O2 x.i -mno-inline-all-stringops -mtune=i386
[hjl@gnu-6 gcc]$ cat x.s
    .file    "x.i"
    .text
    .p2align 2,,3
    .globl    foo
    .type    foo, @function
foo:
.LFB0:
    .cfi_startproc
    pushl    %edi
    .cfi_def_cfa_offset 8
    .cfi_offset 7, -8
    movl    8(%esp), %edi
    xorl    %eax, %eax
    movl    $-1, %ecx
    repnz scasb
    notl    %ecx
    leal    -1(%ecx), %eax
    popl    %edi
    .cfi_restore 7
    .cfi_def_cfa_offset 4
    ret

[hjl@gnu-6 gcc]$ gcc -S -m32 -O2 x.i -mno-inline-all-stringops -mtune=i486
[hjl@gnu-6 gcc]$ cat x.s
    .file    "x.i"
    .text
    .p2align 4,,15
    .globl    foo
    .type    foo, @function
foo:
.LFB0:
    .cfi_startproc
    jmp    strlen