COMPONENT_REF problem ?

[Richard Guenther]

On Sat, Oct 3, 2009 at 12:43 PM, Pranav Bhandarkar
<pranav.bhandarkar@gmail.com> wrote:
> Hi,
>
> Is it possible for a component_ref node to have its arg 0 to be NULL ?
> I would think not because from tree.def I gather that arg 0 tells me
> what structures field this component_ref refers to. For convenience, I
> have pasted here what tree.def tells me about a component_ref
>
>
> /* Value is structure or union component.
>   Operand 0 is the structure or union (an expression).
>   Operand 1 is the field (a node of type FIELD_DECL).
>   Operand 2, if present, is the value of DECL_FIELD_OFFSET, measured
>   in units of DECL_OFFSET_ALIGN / BITS_PER_UNIT.  */
> DEFTREECODE (COMPONENT_REF, "component_ref", tcc_reference, 3)
>
>
> I am working on a target hook wherein I use the MEM_EXPR of a mem rtx.
> It returns the following component_ref node
>
> <component_ref 0x2b3599d0ca00
>    type <integer_type 0x2b35998f1e40 int32 sizes-gimplified public SI
>        size <integer_cst 0x2b359975a840 constant 32>
>        unit size <integer_cst 0x2b359975a4b0 constant 4>
>        align 32 symtab 0 alias set -1 canonical type 0x2b359976d6c0
> precision 32 min <integer_cst 0x2b359975a8a0 -2147483648> max \
> <integer_cst 0x2b359975a8d0 2147483647>
>        pointer_to_this <pointer_type 0x2b3599b1c300>>
>
>    arg 1 <field_decl 0x2b3599b18140 dcfMemL1 type <integer_type
> 0x2b35998f1e40 int32>
>        used nonlocal decl_3 SI file ../src/synth_core/QDSP6/svrreg.h
> line 134 col 11 size <integer_cst 0x2b359975a840 32> unit siz\
> e <integer_cst 0x2b359975a4b0 4>
>        align 32 offset_align 64
>        offset <integer_cst 0x2b3599b04b10 constant 152> bit offset
> <integer_cst 0x2b359975a840 32> context <record_type 0x2b3599b1\
> 2840 dlsSvrReg>
>        chain <field_decl 0x2b3599b181e0 dcfMemL2 type <integer_type
> 0x2b35998f1e40 int32>
>            used nonlocal decl_3 SI file
> ../src/synth_core/QDSP6/svrreg.h line 135 col 11 size <integer_cst
> 0x2b359975a840 32> unit\
>  size <integer_cst 0x2b359975a4b0 4>
>            align 32 offset_align 64
>            offset <integer_cst 0x2b3599b04b70 constant 160>
>            bit offset <integer_cst 0x2b359977e0c0 constant 0> context
> <record_type 0x2b3599b12840 dlsSvrReg> chain <field_decl 0x2\
> b3599b18280 dcfMemR1>>>>
>
>
> Following this if I do
> exp = TREE_OPERAND ( comp_ref_node, 0);
>
> I get "exp" as NULL ?
>
> Is this possible ? or Is there something I am doing wrong ? or There
> is something fishy here with the tree node that MEM_EXPR is giving me
> ?

If you are not working on trunk this can happen because the way
MEM_EXPRs are "canonicalized".

Richard.

> Thanks,
> Pranav
>