On 02/15/2017 05:06 PM, Aldy Hernandez wrote:
> On 02/15/2017 09:49 AM, Martin Liška wrote:
>> Hi.
>>
>> As mentioned in the PR, gimple nops are wrongly handled in
>> is_maybe_undefined function.
>> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
>
>>
>> gimple *def = SSA_NAME_DEF_STMT (t);
>>
>> + if (!def || gimple_nop_p (def))
>> + return true;
>> +
>
>
> Out of curiosity, what is T?
It's a SSA name which belongs to a result_decl:
(gdb) p debug_tree(t)
<ssa_name 0x7fffdaf3b1f8
type <reference_type 0x7ffff122c9d8
type <record_type 0x7ffff0664888 UnicodeString addressable
needs-constructing BLK
size <integer_cst 0x7ffff6892030 constant 512>
unit size <integer_cst 0x7ffff6931c00 constant 64>
align 64 symtab 0 alias set -1 canonical type 0x7ffff66b0e70 fields
<field_decl 0x7ffff0669390 D.165781> context <namespace_decl 0x7ffff66954c0
icu_58>
pointer_to_this <pointer_type 0x7ffff06791f8> reference_to_this
<reference_type 0x7fffea593e70> chain <type_decl 0x7ffff0669428 UnicodeString>>
public unsigned DI
size <integer_cst 0x7ffff6876be8 constant 64>
unit size <integer_cst 0x7ffff6876c00 constant 8>
align 64 symtab 0 alias set -1 structural equality>
var <result_decl 0x7fffdaf1f528 resultPattern>
def_stmt GIMPLE_NOP
version 1
ptr-info 0x7fffcc191000>
>
> Because we early bail out if ssa_undefined_value_p() right before calling
> SSA_NAME_DEF_STMT, and ssa_undefined_value_p() will already bail if
> gimple_nop_p.
>
> So T must be one of:
>
>
> /* Parameters get their initial value from the function entry. */
> else if (TREE_CODE (var) == PARM_DECL)
> return false;
> /* When returning by reference the return address is actually a hidden
> parameter. */
> else if (TREE_CODE (var) == RESULT_DECL && DECL_BY_REFERENCE (var))
> return false;
This return statement is taken.
> /* Hard register variables get their initial value from the ether. */
> else if (VAR_P (var) && DECL_HARD_REGISTER (var))
> return false;
>
> which I wonder if we should special case in is_maybe_undefined.
Do we need a special case in the function?
M.
>
> Aldy
