Making a variable addressable in GIMPLE

[Yoav Etsion]

Hi Diego,

Diego Novillo wrote:
 > Yoav Etsion wrote:
 >
 >
 >>The problem is that the first mudflap pass takes place at the GIMPLE
 >>level, at which point all variables have their
 >>addressable/non-addressable attributes set, which forbids me to build an
 >>ADDR_EXPR node for a non-addressable pointer variable ("invalid operand
 >>to unary & operator" error).
 >>
 >
 > Call build_addr() to create the ADDR_EXPR.  It will set the
 > TREE_ADDRESSABLE bit on the variable and set some attributes on the
 > ADDR_EXPR itself.
 >
The code is nicer, but still no go... :)

 >
 > That message suggest that you may be trying to build the address of a
 > non-decl, though.  Show me the code and an example of your 
transformation?
 >

The transformation is simple: mudflap already injects a call to 
__mf_register when an addressable variable is declared. I want to do the 
same for all pointer variables, so I've added the predicate
POINTER_TYPE_P( TREE_TYPE(decl) )
to the eligibility test (performed on each VAR_DECL node).
gcc is compiled with --enable-checking.

The test code:
 >>>
/* avoid including the entire header. */
extern int printf (const char * __format, ...);

int main()
{
    int data = 15;
    int *data_p = &data;

    printf("%d, %d\n", (int)data_p, data);

    return 0;
}
<<<

The code dump after the first mudflap pass is:
 >>>
{
   intD.0 data.0D.781;
   intD.0 data_p.1D.782;
   intD.0 D.783;
   intD.0 dataD.779;
   intD.0 * data_pD.780;

   try
     {
       __mf_register (&dataD.779, 4, 3, "simple-stack-pointer.c:6 (main) 
data");
       __mf_register (&data_pD.780, 4, 3, "simple-stack-pointer.c:7 
(main) data_p");
       dataD.779 = 15;
       data_pD.780 = &dataD.779;
       data.0D.781 = dataD.779;
       data_p.1D.782 = (intD.0) data_pD.780;
       printf (&"%d, %d\n"[0], data_p.1D.782, data.0D.781);
       D.783 = 0;
       return D.783;
     }
   finally
     {
       __mf_unregister (&dataD.779, 4, 3);
       __mf_unregister (&data_pD.780, 4, 3);
     }
}
<<<

The exact error message is:
 >>>
simple-stack-pointer.c: In function 'main':
simple-stack-pointer.c:5: error: Invalid operand to unary operator
data_pD.780

simple-stack-pointer.c:5: internal compiler error: verify_stmts failed.
please submit...
<<<

The error message directs me to the addressability of 'data_p'.
Any ideas?

Thanks,

Yoav Etsion