On Fri, Mar 8, 2013 at 3:19 PM, Richard Biener
<richard.guent...@gmail.com> wrote:
> On Fri, Mar 8, 2013 at 2:57 PM, Georg-Johann Lay <a...@gjlay.de> wrote:
>> While implementing PR56263 (Strict address-space checking for AVR), I
>> encountered the problem that pointer casts with address spaces are always
>> expanded as const_int 0.
>>
>> The problem occurs if the attached patch that implements PR56263 and the
>> following code is compiled as
>>
>> $ avr-gcc -Os flash-cast.c -S -mstrict-addr-space-subsets
>>
>>
>> #define PROGMEM __attribute__((__progmem__))
>>
>> #define PSTR(s) \
>> (__extension__ \
>> ({ \
>> static const char __c[] PROGMEM = (s); \
>> &__c[0]; \
>> }))
>>
>> extern void print (const __memx char*, ...);
>>
>> const __flash char *p;
>>
>> void f (const char *c)
>> {
>> c = (const char*) p;
>>
>> print ((const __flash char*) PSTR ("Hallo flash"));
>> }
>>
>>
>>
>> The corresponding .expand dump reads:
>>
>>
>> f (const char * c)
>> {
>> static const char __c[12] = "Hallo flash";
>> const <address-space-1> char * _2;
>> const <address-space-7> char * _3;
>>
>> ;; basic block 2, loop depth 0
>> ;; pred: ENTRY
>> _2 = (const <address-space-1> char *) (&__c[0]);
>> _3 = (const <address-space-7> char *) _2;
>> print (_3); [tail call]
>> return;
>> ;; succ: EXIT
>>
>> }
>>
>>
>> but the expression is always emit as (const_int 0).
>>
>>
>> Trying to track this issue, I ended up in build1_stat which enters the
>> default
>> case for "code" (ADDR_SPACE_CONVERT_EXPR at that time) and returns the
>> following tree:
>>
>>
>> (gdb) p t
>> $62 = (tree) 0xb7bb4578
>> (gdb) pt
>> <addr_space_convert_expr 0xb7bb4578
>> type <pointer_type 0xb7bc3a80
>> type <integer_type 0xb7bc3a20 char readonly sizes-gimplified
>> address-space-1 string-flag QI
>> size <integer_cst 0xb7b3a1a4 constant 8>
>> unit size <integer_cst 0xb7b3a1b8 constant 1>
>> align 8 symtab 0 alias set -1 canonical type 0xb7bc3a20
>> precision 8
>> min <integer_cst 0xb7b3a1e0 -128> max <integer_cst 0xb7b3a208 127>
>> pointer_to_this <pointer_type 0xb7bc3a80>>
>> unsigned HI
>> size <integer_cst 0xb7b3a08c constant 16>
>> unit size <integer_cst 0xb7b3a0a0 constant 2>
>> align 8 symtab 0 alias set -1 canonical type 0xb7bc3a80>
>> readonly constant
>> arg 0 <addr_expr 0xb7bb449c
>> type <pointer_type 0xb7b4f2a0 type <integer_type 0xb7b4f240 char>
>> public unsigned HI size <integer_cst 0xb7b3a08c 16> unit size
>> <integer_cst 0xb7b3a0a0 2>
>> align 8 symtab 0 alias set -1 canonical type 0xb7b4f2a0
>> pointer_to_this <pointer_type 0xb7b4f840>>
>> readonly constant
>> arg 0 <array_ref 0xb7b465a0 type <integer_type 0xb7b4f240 char>
>> readonly arg 0 <var_decl 0xb7bcd05c __c>
>> arg 1 <integer_cst 0xb7b3a460 constant 0>
>> flash-cast.c:18:128>
>> flash-cast.c:18:124>>
>>
>> Problem is the arg 1 <integer_cst 0xb7b3a460 constant 0> at the end which
>> leads
>> to the expansion of 0.
>>
>> The call chain is:
>>
>> #0 build1_stat (code=ADDR_SPACE_CONVERT_EXPR, type=0xb7bc3a80,
>> node=0xb7bb449c) at ../../../gcc.gnu.org/trunk/gcc/tree.c:3848
>> (gdb) bt
>> #0 build1_stat (code=ADDR_SPACE_CONVERT_EXPR, type=0xb7bc3a80,
>> node=0xb7bb449c) at ../../../gcc.gnu.org/trunk/gcc/tree.c:3848
>> #1 0x08286be0 in gimple_assign_rhs_to_tree (stmt=0xb7bc2c30) at
>> ../../../gcc.gnu.org/trunk/gcc/cfgexpand.c:86
>> #2 0x0837047f in expand_expr_real_1 (exp=0xb7b972f8, target=0x0,
>> tmode=VOIDmode, modifier=EXPAND_STACK_PARM, alt_rtl=0x0) at
>> ../../../gcc.gnu.org/trunk/gcc/expr.c:9274
>> #3 0x083762f2 in expand_expr_real (exp=0xb7b972f8, target=0x0,
>> tmode=VOIDmode,
>> modifier=EXPAND_STACK_PARM, alt_rtl=0x0) at
>> ../../../gcc.gnu.org/trunk/gcc/expr.c:7863
>> #4 0x08376a7e in expand_expr (exp=0xb7b972f8, target=0x0, mode=VOIDmode,
>> modifier=EXPAND_STACK_PARM) at ../../../gcc.gnu.org/trunk/gcc/expr.h:444
>> #5 0x0836ae96 in expand_expr_real_2 (ops=0xbfffca10, target=0x0,
>> tmode=VOIDmode, modifier=EXPAND_STACK_PARM) at
>> ../../../gcc.gnu.org/trunk/gcc/expr.c:8150
>> #6 0x08376234 in expand_expr_real_1 (exp=0xb7bb4564, target=0x0,
>> tmode=VOIDmode, modifier=EXPAND_STACK_PARM, alt_rtl=0x0) at
>> ../../../gcc.gnu.org/trunk/gcc/expr.c:10491
>> #7 0x083762f2 in expand_expr_real (exp=0xb7bb4564, target=0x0,
>> tmode=VOIDmode,
>> modifier=EXPAND_STACK_PARM, alt_rtl=0x0) at
>> ../../../gcc.gnu.org/trunk/gcc/expr.c:7863
>> #8 0x083704a6 in expand_expr_real_1 (exp=0xb7b97320, target=0x0,
>> tmode=VOIDmode, modifier=EXPAND_STACK_PARM, alt_rtl=0x0) at
>> ../../../gcc.gnu.org/trunk/gcc/expr.c:9274
>> #9 0x083762f2 in expand_expr_real (exp=0xb7b97320, target=0x0,
>> tmode=VOIDmode,
>> modifier=EXPAND_STACK_PARM, alt_rtl=0x0) at
>> ../../../gcc.gnu.org/trunk/gcc/expr.c:7863
>> #10 0x0826ae1a in expand_expr (exp=0xb7b97320, target=0x0, mode=VOIDmode,
>> modifier=EXPAND_STACK_PARM) at ../../../gcc.gnu.org/trunk/gcc/expr.h:444
>> #11 0x0826c215 in store_one_arg (arg=0xbfffd130, argblock=0x0, flags=0,
>> variable_size=0, reg_parm_stack_space=0) at
>> ../../../gcc.gnu.org/trunk/gcc/calls.c:4500
>> #12 0x08274d79 in expand_call (exp=0xb7b46640, target=0x0, ignore=1) at
>> ../../../gcc.gnu.org/trunk/gcc/calls.c:3040
>> #13 0x08375088 in expand_expr_real_1 (exp=0xb7b46640, target=0x0,
>> tmode=VOIDmode, modifier=EXPAND_NORMAL, alt_rtl=0x0) at
>> ../../../gcc.gnu.org/trunk/gcc/expr.c:10209
>> #14 0x0828cb86 in expand_call_stmt (stmt=0xb7fde140) at
>> ../../../gcc.gnu.org/trunk/gcc/cfgexpand.c:2114
>>
>> ...
>>
>>
>> The problem comes apparent in #5 expand_expr_real_2
>>
>> if (targetm.addr_space.subset_p (as_to, as_from)
>> || targetm.addr_space.subset_p (as_from, as_to))
>> {
>> op0 = expand_expr (treeop0, NULL_RTX, VOIDmode, modifier);
>> op0 = targetm.addr_space.convert (op0, treeop0_type, type);
>> gcc_assert (op0);
>> return op0;
>> }
>>
>> where op0 is const0_rtx and targetm.addr_space.convert cannot recover from
>> that.
>>
>> Maybe someone can help me fixing the root cause?
>
> Doesn't make sense - in the above code treeop0 should be the
>
> arg 0 <addr_expr 0xb7bb449c
>
> not the zero integer constant.
The first conversion expands to
(symbol_ref:HI ("__c.1466") [flags 0x202] <var_decl 0x7ffff6dfaa18 __c>)
then we try to convert that to another address-space and the target hook
returns
(insn 6 0 7 (set (reg/f:HI 46)
(symbol_ref:HI ("__c.1466") [flags 0x202] <var_decl
0x7ffff6dfaa18 __c>)) t.c:18 -1
(nil))
(insn 7 6 0 (set (reg:PSI 45)
(zero_extend:PSI (reg/f:HI 46))) t.c:18 -1
(nil))
(reg:PSI 45)
so the issue must be elsewhere (in case the above is correct).
-mstrict-addr-space-subsets
doesn't exist for me.
Richard.
>> the incoming "node" in build1_stat has already arg 1 <integer_cst constant 0>
>>
>> Thanks.
>>
>> Johann
>>
