[Bug tree-optimization/35833] New: Wrong code generated with -ftree-vrp

[qrczak at knm dot org dot pl]

This is not vanilla 4.3.0 but gcc-4_3-branch from 
2008-03-13.

Here is a source:

struct S {struct S *field;};
extern struct S True, False, Z;
static inline int f(void) {return 1;}
static inline int g(struct S **obj) {
   return f() && *obj == &Z;
}
struct S **h(struct S **x) {
   if (x)
      return g(x) ? &True.field : &False.field;
   else
      return &True.field;
}

"gcc -S -O -ftree-vrp bug.c" produces the following code for h:

h:
        pushl   %ebp
        movl    $True, %eax
        movl    %esp, %ebp
        leave
        ret

This is obviously wrong: there are condidions when it should return
&False.field.

The bug is not triggered without -ftree-vrp, or after minor modifications like
manually inlining f() or g(). A correct code:

h:
        pushl   %ebp
        movl    $True, %eax
        movl    %esp, %ebp
        movl    8(%ebp), %edx
        testl   %edx, %edx
        je      .L3
        cmpl    $Z, (%edx)
        movl    $True, %eax
        je      .L3
        movl    $False, %eax
.L3:
        leave
        ret


-- 
           Summary: Wrong code generated with -ftree-vrp
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: qrczak at knm dot org dot pl
 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=35833