[Bug target/52208] New: [4.7 Regression] Useless store

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52208

             Bug #: 52208
           Summary: [4.7 Regression] Useless store
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: hjl.to...@gmail.com
                CC: ubiz...@gmail.com
            Target: x86_64


[hjl@gnu-6 pr52146]$ cat a.i
int test5() {
  int* apic_tpr_addr = (int *)0xfee00080;
  return *apic_tpr_addr + 5;
}
[hjl@gnu-6 pr52146]$ gcc -S -O a.i
[hjl@gnu-6 pr52146]$ cat a.s
    .file    "a.i"
    .text
    .globl    test5
    .type    test5, @function
test5:
.LFB0:
    .cfi_startproc
    movabsl    4276093056, %eax
    addl    $5, %eax
    ret
    .cfi_endproc
.LFE0:
    .size    test5, .-test5
    .ident    "GCC: (GNU) 4.6.1 20110908 (Red Hat 4.6.1-9)"
    .section    .note.GNU-stack,"",@progbits
[hjl@gnu-6 pr52146]$ /export/build/gnu/gcc/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc/build-x86_64-linux/gcc/ -S  -O   a.i  
[hjl@gnu-6 pr52146]$ cat a.s
    .file    "a.i"
    .text
    .globl    test5
    .type    test5, @function
test5:
.LFB0:
    .cfi_startproc
    movabsl    4276093056, %eax
    movl    %eax, -4(%rsp)
    addl    $5, %eax
    ret
    .cfi_endproc
.LFE0:
    .size    test5, .-test5
    .ident    "GCC: (GNU) 4.7.0 20120209 (experimental)"
    .section    .note.GNU-stack,"",@progbits
[hjl@gnu-6 pr52146]$ 

GCC 4.7 generates extra store:

movl    %eax, -4(%rsp)