On 03 Jun 17:27, Ilya Enkovich wrote:
> 2014-06-03 15:56 GMT+04:00 Richard Biener <richard.guent...@gmail.com>:
> > On Tue, Jun 3, 2014 at 1:36 PM, Ilya Enkovich <enkovich....@gmail.com>
> > wrote:
> >> 2014-06-03 13:45 GMT+04:00 Richard Biener <richard.guent...@gmail.com>:
> >>> On Tue, Jun 3, 2014 at 9:23 AM, Ilya Enkovich <enkovich....@gmail.com>
> >>> wrote:
> >>>> Hi,
> >>>>
> >>>> This patch adjusts alloc-free removal algorithm in DCE to take into
> >>>> account BUILT_IN_CHKP_BNDRET call returning bounds of allocated memory.
> >>>>
> >>>> Bootstrapped and tested on linux-x86_64.
> >>>>
> >>>> Thanks,
> >>>> Ilya
> >>>> --
> >>>> gcc/
> >>>>
> >>>> 2014-06-03 Ilya Enkovich <ilya.enkov...@intel.com>
> >>>>
> >>>> * tree-ssa-dce.c: Include target.h.
> >>>> (propagate_necessity): For free call fed by alloc check
> >>>> bounds are also provided by the same alloc.
> >>>> (eliminate_unnecessary_stmts): Handle BUILT_IN_CHKP_BNDRET
> >>>> used by free calls.
> >>>>
> >>>> diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
> >>>> index 13a71ce..59a0b71 100644
> >>>> --- a/gcc/tree-ssa-dce.c
> >>>> +++ b/gcc/tree-ssa-dce.c
> >>>> @@ -73,6 +73,7 @@ along with GCC; see the file COPYING3. If not see
> >>>> #include "flags.h"
> >>>> #include "cfgloop.h"
> >>>> #include "tree-scalar-evolution.h"
> >>>> +#include "target.h"
> >>>>
> >>>> static struct stmt_stats
> >>>> {
> >>>> @@ -778,7 +779,23 @@ propagate_necessity (bool aggressive)
> >>>> && DECL_BUILT_IN_CLASS (def_callee) == BUILT_IN_NORMAL
> >>>> && (DECL_FUNCTION_CODE (def_callee) == BUILT_IN_MALLOC
> >>>> || DECL_FUNCTION_CODE (def_callee) ==
> >>>> BUILT_IN_CALLOC))
> >>>> - continue;
> >>>> + {
> >>>> + tree retfndecl
> >>>> + = targetm.builtin_chkp_function
> >>>> (BUILT_IN_CHKP_BNDRET);
> >>>> + gimple bounds_def_stmt;
> >>>> + tree bounds;
> >>>> +
> >>>> + /* For instrumented calls we should also check used
> >>>> + bounds are returned by the same allocation call. */
> >>>> + if (!gimple_call_with_bounds_p (stmt)
> >>>> + || ((bounds = gimple_call_arg (stmt, 1))
> >>>
> >>> Please provide an abstraction for this - I seem to recall seeing multiple
> >>> (variants) of this. Esp. repeated calls to the target hook above look
> >>> expensive to me (generally it will not be needed).
> >>>
> >>> I'd like to see gimple_call_bndarg (stmt) to get rid of the "magic" 1 and
> >>> I'd
> >>> like to see sth similar to gimple_call_builtin_p, for example
> >>> gimple_call_chkp_p (stmt, BUILT_IN_CHKP_BNDRET) doing the
> >>> target hook invocation and the fndecl check.
> >>
> >> I do not see how to get rid of constant in gimple_call_arg call here.
> >> What semantics does proposed gimple_call_bndarg have? It has to return
> >> the first bounds arg but it's not clear from its name and function
> >> seems to be very specialized.
> >
> > Ah, ok. I see now, so the code is ok as-is.
> >
> >>>
> >>>> + && TREE_CODE (bounds) == SSA_NAME
> >>>
> >>> What about constant bounds? That shouldn't make the call necessary
> >>> either?
> >>
> >> Yep, it would be useless.
> >
> > So please fix.
> >
> >>>
> >>>> + && (bounds_def_stmt = SSA_NAME_DEF_STMT
> >>>> (bounds))
> >>>> + && is_gimple_call (bounds_def_stmt)
> >>>> + && gimple_call_fndecl (bounds_def_stmt) ==
> >>>> retfndecl
> >>>> + && gimple_call_arg (bounds_def_stmt, 0) ==
> >>>> ptr))
> >>>> + continue;
> >>>
> >>> So this all becomes
> >>>
> >>> if (!gimple_call_with_bounds_p (stmt)
> >>> || ((bounds = gimple_call_bndarg (stmt))
> >>> && TREE_CODE (bounds) == SSA_NAME
> >>> && (bounds_def_stmt = SSA_NAME_DEF_STMT
> >>> (bounds))
> >>> && is_gimple_call (bounds_def_stmt)
> >>> && gimple_call_chkp_p (bounds_def_stmt,
> >>> BUILT_IN_CHKP_BNDRET)
> >>> ...
> >>>
> >>> btw, I wonder how BUILT_IN_CHKP_BNDRET is in scope here but you
> >>> need a target hook to compare the fndecl? Why isn't it enough to
> >>> just check DECL_FUNCTION_CODE and DECL_BUILT_IN?
> >>
> >> Call is required because builtins for Pointer Bounds Checker are
> >> provided by target depending on available features. That is why
> >> gimple_call_builtin_p is not used. I may add new interface function
> >> into tree-chkp.h as you propose (e.g. chkp_gimple_call_builtin_p). But
> >> I do not see how it may speed-up the code. New function would still
> >> need to switch by function code and compare with proper decl which is
> >> basically what we have with target hook.
> >
> > I don't understand - does this mean the builtin calls are in the GIMPLE
> > IL even though the target doesn't have the feature? Isn't the presence
> > of the call enough?
>
> Call is generated using function decl provided by target. Therefore we
> do not know its code and has to compare using fndecl comparison.
>
> >
> >> It is possible to make faster if use the fact that all chkp builtins
> >> codes (normal, not target ones) are consequent. Then we may just check
> >> the range and use code as an index in array of chkp fndecls to compare
> >> decls. Would it be OK to rely on builtin codes numbering?
> >
> > Yes, but that's not my point here. In the above code the target hook
> > is called all the time, even if !gimple_call_with_bounds_p (). Providing
> > a suitable abstraction (or simply relying on DECL_FUNCTION_CODE)
> > should fix that.
>
> Got it. Will fix.
>
> Thanks,
> Ilya
>
Here is a fixed version.
Bootstrapped and tested on linux_x86-64.
Thanks,
Ilya
--
gcc/
2014-06-05 Ilya Enkovich <ilya.enkov...@intel.com>
* tree-ssa-dce.c: Include tree-chkp.h.
(propagate_necessity): For free call fed by alloc check
bounds are also provided by the same alloc.
(eliminate_unnecessary_stmts): Handle BUILT_IN_CHKP_BNDRET
used by free calls.
diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index 13a71ce..f186706 100644
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -73,6 +73,7 @@ along with GCC; see the file COPYING3. If not see
#include "flags.h"
#include "cfgloop.h"
#include "tree-scalar-evolution.h"
+#include "tree-chkp.h"
static struct stmt_stats
{
@@ -778,7 +779,22 @@ propagate_necessity (bool aggressive)
&& DECL_BUILT_IN_CLASS (def_callee) == BUILT_IN_NORMAL
&& (DECL_FUNCTION_CODE (def_callee) == BUILT_IN_MALLOC
|| DECL_FUNCTION_CODE (def_callee) == BUILT_IN_CALLOC))
- continue;
+ {
+ gimple bounds_def_stmt;
+ tree bounds;
+
+ /* For instrumented calls we should also check used
+ bounds are returned by the same allocation call. */
+ if (!gimple_call_with_bounds_p (stmt)
+ || ((bounds = gimple_call_arg (stmt, 1))
+ && TREE_CODE (bounds) == SSA_NAME
+ && (bounds_def_stmt = SSA_NAME_DEF_STMT (bounds))
+ && is_gimple_call (bounds_def_stmt)
+ && chkp_gimple_call_builtin_p (bounds_def_stmt,
+ BUILT_IN_CHKP_BNDRET)
+ && gimple_call_arg (bounds_def_stmt, 0) == ptr))
+ continue;
+ }
}
FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
@@ -1204,6 +1220,23 @@ eliminate_unnecessary_stmts (void)
&& !gimple_plf (def_stmt, STMT_NECESSARY))
gimple_set_plf (stmt, STMT_NECESSARY, false);
}
+ /* We did not propagate necessity for free calls fed
+ by allocation function to allow unnecessary
+ alloc-free sequence elimination. For instrumented
+ calls it also means we did not mark bounds producer
+ as necessary and it is time to do it in case free
+ call is not removed. */
+ if (gimple_call_with_bounds_p (stmt))
+ {
+ gimple bounds_def_stmt;
+ tree bounds = gimple_call_arg (stmt, 1);
+ gcc_assert (TREE_CODE (bounds) == SSA_NAME);
+ bounds_def_stmt = SSA_NAME_DEF_STMT (bounds);
+ if (bounds_def_stmt
+ && !gimple_plf (bounds_def_stmt, STMT_NECESSARY))
+ gimple_set_plf (bounds_def_stmt, STMT_NECESSARY,
+ gimple_plf (stmt, STMT_NECESSARY));
+ }
}
/* If GSI is not necessary then remove it. */
@@ -1233,7 +1266,9 @@ eliminate_unnecessary_stmts (void)
&& DECL_FUNCTION_CODE (call) != BUILT_IN_CALLOC
&& DECL_FUNCTION_CODE (call) != BUILT_IN_ALLOCA
&& (DECL_FUNCTION_CODE (call)
- != BUILT_IN_ALLOCA_WITH_ALIGN))))
+ != BUILT_IN_ALLOCA_WITH_ALIGN)))
+ /* Avoid doing so for bndret calls for the same reason. */
+ && !chkp_gimple_call_builtin_p (stmt, BUILT_IN_CHKP_BNDRET))
{
something_changed = true;
if (dump_file && (dump_flags & TDF_DETAILS))
