[Bug rtl-optimization/23488] New: extra reads from static variable

[dann at godzilla dot ics dot uci dot edu]

typedef int nl_item;

extern char *nl_langinfo (nl_item __item) __attribute__ ((__nothrow__));

char *
xtermEnvEncoding(void)
{
  static char *result;

  if (result == 0) {

    result = nl_langinfo(1);
    ;
  }
  return result;
}

Compile the above code with -march=i686 -O2 
4.1 generates extra reads to the static result.1282.


xtermEnvEncoding:
        pushl   %ebp
        movl    %esp, %ebp
        subl    $8, %esp
        movl    result.1282, %eax
        testl   %eax, %eax
        je      .L6
        movl    result.1282, %eax   <--- this one
        leave
        ret
        .p2align 4,,7
.L6:
        movl    $1, (%esp)
        call    nl_langinfo
        movl    %eax, result.1282   
        movl    result.1282, %eax  <-- and this one
        leave
        ret


4.0 does not generate those instructions.
This is one of the reasons for the code size regression in PR23153.

-- 
           Summary: extra reads from static variable
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dann at godzilla dot ics dot uci dot edu
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i686-pc-linux.-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23488