Procedure Pointers: a first patch

[Steven Bosscher]

xf. http://gcc.gnu.org/ml/fortran/2008-05/msg00029.html

Hi Janus,

Just for comparison, look at the gimple for the following C test case
with your Fortran tree:

================
extern void foo (void);
void bar (void) {
  typedef void (*funptr) (void);
  funptr ptr = foo;
}
================
This gives the following statement to the gimplifier:

Breakpoint 5, gimplify_stmt (stmt_p=0x22c760) at
../../vanilla/gcc/gimplify.c:4660
4660	  gimplify_expr (stmt_p, NULL, NULL, is_gimple_stmt, fb_none);
(gdb) p debug_tree(*stmt_p)
 <init_expr 0x7ff40208
    type <void_type 0x7ff81248 void VOID
        align 8 symtab 0 alias set -1 canonical type 0x7ff81248
        pointer_to_this <pointer_type 0x7ff812b0>>
    side-effects
    arg 0 <var_decl 0x7fdf0000 ptr
        type <pointer_type 0x7ff8f908 funptr type <function_type 0x7ff837a8>
            sizes-gimplified unsigned SI
            size <integer_cst 0x7ff00700 constant 32>
            unit size <integer_cst 0x7ff004a0 constant 4>
            align 32 symtab 0 alias set -1 canonical type 0x7ff8f838>
        unsigned SI file t.c line 6 col 10 size <integer_cst
0x7ff00700 32> unit size <integer_cst 0x7ff004a0 4>
        align 32 context <function_decl 0x7fdbf340 bar>>
    arg 1 <addr_expr 0x7fde2500
        type <pointer_type 0x7ff8f838 type <function_type 0x7ff837a8>
            sizes-gimplified unsigned SI size <integer_cst 0x7ff00700
32> unit size <integer_cst 0x7ff004a0 4>
            align 32 symtab 0 alias set -1 canonical type 0x7ff8f838>
        constant
        arg 0 <function_decl 0x7fdbf2d0 foo type <function_type 0x7ff837a8>
            addressable used public external decl_5 QI defer-output
file t.c line 1 col 13 align 8>>>

Note how the rhs of the assignment arg0 (INIT_EXPR is gimplified to a
simple assignment) is a var decl.

For your test case, otoh, I get an ADDR_EXPR on the rhs:

#4  0x007876cd in gimplify_stmt (stmt_p=0x7ff33c08) at
../../vanilla/gcc/gimplify.c:4660
4660	  gimplify_expr (stmt_p, NULL, NULL, is_gimple_stmt, fb_none);
(gdb) p debug_tree(*stmt_p)
 <modify_expr 0x7ff401e0
    type <void_type 0x7ff808f0 void VOID
        align 8 symtab 0 alias set -1 canonical type 0x7ff808f0
        pointer_to_this <pointer_type 0x7ff80958>>
    side-effects
    arg 0 <addr_expr 0x7fdb0bc0
        type <pointer_type 0x7ff82be0 type <function_type 0x7ff82b78>
            unsigned SI
            size <integer_cst 0x7ff006e0 constant 32>
            unit size <integer_cst 0x7ff00480 constant 4>
            align 32 symtab 0 alias set -1 canonical type 0x7ff82be0>
        constant
        arg 0 <function_decl 0x7ff9c1d0 ptr type <function_type 0x7ff82b78>
            addressable public external QI file procptr.f90 line 13
col 0 align 8 chain <function_decl 0x7ff9c160 procptrtest>>>
    arg 1 <addr_expr 0x7fdb0c00 type <pointer_type 0x7ff82be0>
        constant
        arg 0 <function_decl 0x7ff9c240 proc type <function_type 0x7ff82b78>
            addressable public external QI file procptr.f90 line 13
col 0 align 8 chain <function_decl 0x7ff9c1d0 ptr>>>
    procptr.f90:20:0>


Full GDB output is attached for your convenience.
Hope this helps!

Gr.
Steven
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