[Bug c/35729] New: const volatile variable accessed that should not be

[regehr at cs dot utah dot edu]

This is for "gcc version 4.3.0 (GCC)" 

func_1() here should never load from g_361 since the loop body never executes:

  const volatile int g_361 = 3L;
  volatile int g_2 = 0L;
  void func_1 (void) {
    for (g_2 = 0; g_2 > 10; g_2++)
      {
        int l_357 = g_361;
      }
  }

However when compiled with "gcc -Os -S foo.c" we get the following output which
does load from g_361:

        .file   "foo.c"
        .text
.globl func_1
        .type   func_1, @function
func_1:
        pushl   %ebp
        movl    %esp, %ebp
        movl    $0, g_2
        movl    g_361, %eax
        jmp     .L2
.L3:
        movl    g_2, %eax
        incl    %eax
        movl    %eax, g_2
.L2:
        movl    g_2, %eax
        cmpl    $10, %eax
        jg      .L3
        popl    %ebp
        ret
        .size   func_1, .-func_1
.globl g_361
        .data
        .align 4
        .type   g_361, @object
        .size   g_361, 4
g_361:
        .long   3
.globl g_2
        .bss
        .align 4
        .type   g_2, @object
        .size   g_2, 4
g_2:
        .zero   4
        .ident  "GCC: (GNU) 4.3.0"
        .section        .note.GNU-stack,"",@progbits

At -O0, -O1, and -O2 there is no problem.


-- 
           Summary: const volatile variable accessed that should not be
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: regehr at cs dot utah dot edu
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35729