------- Comment #4 from rguenther at suse dot de 2007-07-11 08:45 -------
Subject: Re: CCP removes volatile qualifiers.
On Tue, 10 Jul 2007, ramana dot radhakrishnan at celunite dot com wrote:
> (In reply to comment #2)
> > As the decl is volatile as well this is clearly a bogus optimization.
> >
>
> Putting a breakpoint on evaluate_stmt in tree-ssa-ccp.c shows that stmt_ann of
> the stmt does not have has_volatile_ops set to true.
>
>
> (gdb) p stmt
> (gdb) pt
> <gimple_modify_stmt 0xb7d4fee0 side-effects
> arg 0 <ssa_name 0xb7d4aed4
> type <pointer_type 0xb7d44bd0 type <integer_type 0xb7d44b64 int>
> sizes-gimplified unsigned SI
> size <integer_cst 0xb7caa460 constant invariant 32>
> unit size <integer_cst 0xb7caa24c constant invariant 4>
> align 32 symtab 0 alias set -1 canonical type 0xb7d44bd0>
> visited var <var_decl 0xb7d5005c spinlock0> def_stmt
> <gimple_modify_stmt 0xb7d4fee0>
> version 1>
> arg 1 <addr_expr 0xb7d481c0 type <pointer_type 0xb7d44bd0>
> constant invariant
> arg 0 <array_ref 0xb7cb5084 type <integer_type 0xb7d44b64 int>
> arg 0 <var_decl 0xb7d50000 spinlock>
> arg 1 <integer_cst 0xb7d4fec4 constant invariant 0>>>
> try.c:5>
> (gdb) (gdb) p *(stmt->base->ann)
> $17 = {common = {type = STMT_ANN, aux = 0x0, value_handle = 0x0}, vdecl = {
> common = {type = STMT_ANN, aux = 0x0, value_handle = 0x0},
> out_of_ssa_tag = 0, base_var_processed = 0, used = 0,
> need_phi_state = NEED_PHI_STATE_NO, in_vuse_list = 1, in_vdef_list = 0,
> is_heapvar = 0, call_clobbered = 1, noalias_state = NO_ALIAS_GLOBAL,
> mpt = 0xb7cb6804, symbol_mem_tag = 0x0, partition = 0, base_index = 0,
> current_def = 0x0, subvars = 0x0, escape_mask = 3084210192}, fdecl = {
> common = {type = STMT_ANN, aux = 0x0, value_handle = 0x0},
> reference_vars_info = 0xb7eed528}, stmt = {common = {type = STMT_ANN,
> aux = 0x0, value_handle = 0x0}, bb = 0xb7eed528, operands = {
> def_ops = 0xb7cb6804, use_ops = 0x0, vdef_ops = 0x0, vuse_ops = 0x0,
> stores = 0x0, loads = 0x0}, addresses_taken = 0xb7d55010, uid = 0,
> references_memory = 0, modified = 0, has_volatile_ops = 0,
> makes_clobbering_call = 0}}
>
> Shouldn't has_volatile_ops get set to true in this case because the stmt
> essentially has one volatile operand here ?
No, this assignment just assigns pointers (the pointers are not volatile,
just the thing they point to is). Basically volatile ops is set only
on statements reading/writing memory.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32721
