The patch, or a slight variation (attached), in the PR allows us to
generate better ranges be recomputing longer instruction sequences on
outgoing edges.
This in fact also fixes
XPASS: gcc.dg/Walloca-13.c (test for bogus messages, line 11)
<bb 2> [local count: 1073741824]:
_1 = p_5(D) - q_6(D);
_2 = _1 /[ex] 4;
n_7 = (long unsigned int) _2;
_11 = (long unsigned int) _1;
if (_11 <= 396)
goto <bb 3>; [33.00%]
else
goto <bb 4>; [67.00%]
<bb 3> [local count: 354334800]:
_3 = __builtin_alloca (n_7);
Where _2 was recomputed before, but n_7 was not. Now it is, and we
correctly do not issue the warning any more. awesome.,
however, as seems to be the case often, better ranges result in, I now get:
FAIL: 23_containers/vector/bool/allocator/copy.cc (test for excess errors)
because we now generate:
/opt/notnfs/amacleod/master/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/stl_algobase.h:437:
warning: ‘void* __builtin_memmove(void*, const void*, long unsigned
int)’ writing between 9 and 9223372036854775807 bytes into a region of
size 8 overflows the destination [-Wstringop-overflow=]
I see:
<BB 2>
....
_216 = operator new (8);
_216 : [irange] long unsigned int * [1, +INF]
......
<bb 8> [local count: 86938296]:
D.245552 ={v} {CLOBBER(eol)};
_74 = v1.D.217578._M_impl.D.217043._M_start.D.58619._M_p;
_638 = (long int) _74;
_261 = -_638;
_383 = (long unsigned int) _261;
if (_638 < -8)
goto <bb 12>; [90.00%]
else
goto <bb 13>; [10.00%]
_261 : [irange] long int [-9223372036854775807, +INF]
_383 : [irange] long unsigned int [0,
9223372036854775807][9223372036854775809, +INF]
8->12 (T) _74 : [irange] _Bit_type * [1, +INF]
8->12 (T) _261 : [irange] long int [9, +INF] NONZERO
0x7fffffffffffffff
8->12 (T) _383 : [irange] long unsigned int [9,
9223372036854775807] NONZERO 0x7fffffffffffffff
8->12 (T) _638 : [irange] long int [-INF, -9]
=========== BB 12 ============
_74 [irange] _Bit_type * [9223372036854775808, 18446744073709551607]
_383 [irange] long unsigned int [9, 9223372036854775807] NONZERO
0x7fffffffffffffff
<bb 12> [local count: 78244465]:
__builtin_memmove (_216, _74, _383);
The change is that we now recompute _383 which we didnt before. so we
are seeing memmove being called on what is effectively:
memmove (operator new (8), _74, [9, 9223372036854775807])
And thus the warning.
IS this one of the warnings that has been causing issues? and now Im
triggering it again?
Back at fixup_cfg3 time, it looks like:
_261 = __last$D58797$_M_p_245 - _247;
_262 = _261 > 8;
_263 = (long int) _262;
_264 = __builtin_expect (_263, 1);
if (_264 != 0)
goto <bb 47>; [90.00%]
else
goto <bb 48>; [10.00%]
..................
<bb 47> [local count: 78244465]:
_265 = (long unsigned int) _261;
__builtin_memmove (_246, _247, _265);
So the builtin expect certainly implies it is expecting to have a value > 8
Early on the code looks like:
_1 = __last_10(D) - __first_11(D);
_Num_12 = _1 /[ex] 8;
_2 = _Num_12 > 1;
_3 = (long int) _2;
_4 = __builtin_expect (_3, 1);
if (_4 != 0)
goto <bb 3>; [INV]
else
goto <bb 4>; [INV]
<bb 3> :
_Num.28_5 = (long unsigned int) _Num_12;
_6 = _Num.28_5 * 8;
__builtin_memmove (__result_14(D), __first_11(D), _6);
SO it does still do basically the same thing.
Im not sure whether this is pointing out something real or another false
positive...
Andrew
commit 358d0ca44faf2e20fbacd0f74386308b5ca52cd4
Author: Andrew MacLeod <amacl...@redhat.com>
Date: Tue Mar 28 12:16:34 2023 -0400
Add recursive GORI recompuations with a depth limit.
diff --git a/gcc/gimple-range-gori.cc b/gcc/gimple-range-gori.cc
index 6e8dfa85ca8..5f4313b27dd 100644
--- a/gcc/gimple-range-gori.cc
+++ b/gcc/gimple-range-gori.cc
@@ -1308,7 +1308,7 @@ gori_compute::compute_operand1_and_operand2_range (vrange &r,
// direct dependent is exported, it may also change the computed value of NAME.
bool
-gori_compute::may_recompute_p (tree name, basic_block bb)
+gori_compute::may_recompute_p (tree name, basic_block bb, int depth)
{
tree dep1 = depend1 (name);
tree dep2 = depend2 (name);
@@ -1322,22 +1322,36 @@ gori_compute::may_recompute_p (tree name, basic_block bb)
if (is_a<gphi *> (s) || gimple_has_side_effects (s))
return false;
- // If edge is specified, check if NAME can be recalculated on that edge.
- if (bb)
- return ((is_export_p (dep1, bb))
- || (dep2 && is_export_p (dep2, bb)));
+ if (!dep2)
+ {
+ // -1 indicates a default param, convert it to the real default.
+ if (depth == -1)
+ {
+ depth = (int)param_ranger_recompute_depth;
+ gcc_checking_assert (depth >= 1);
+ }
- return (is_export_p (dep1)) || (dep2 && is_export_p (dep2));
+ bool res = (bb ? is_export_p (dep1, bb) : is_export_p (dep1));
+ if (res || depth <= 1)
+ return res;
+ // Check another level of recomputation.
+ return may_recompute_p (dep1, bb, --depth);
+ }
+ // Two dependencies terminate the depth of the search.
+ if (bb)
+ return is_export_p (dep1, bb) || is_export_p (dep2, bb);
+ else
+ return is_export_p (dep1) || is_export_p (dep2);
}
// Return TRUE if NAME can be recomputed on edge E. If any direct dependent
// is exported on edge E, it may change the computed value of NAME.
bool
-gori_compute::may_recompute_p (tree name, edge e)
+gori_compute::may_recompute_p (tree name, edge e, int depth)
{
gcc_checking_assert (e);
- return may_recompute_p (name, e->src);
+ return may_recompute_p (name, e->src, depth);
}
diff --git a/gcc/gimple-range-gori.h b/gcc/gimple-range-gori.h
index 0fc90ec8a18..3ea4b45595b 100644
--- a/gcc/gimple-range-gori.h
+++ b/gcc/gimple-range-gori.h
@@ -172,8 +172,8 @@ private:
bool refine_using_relation (tree op1, vrange &op1_range,
tree op2, vrange &op2_range,
fur_source &src, relation_kind k);
- bool may_recompute_p (tree name, edge e);
- bool may_recompute_p (tree name, basic_block bb = NULL);
+ bool may_recompute_p (tree name, edge e, int depth = -1);
+ bool may_recompute_p (tree name, basic_block bb = NULL, int depth = -1);
bool compute_operand_range_switch (vrange &r, gswitch *s, const vrange &lhs,
tree name, fur_source &src);
bool compute_operand1_range (vrange &r, gimple_range_op_handler &handler,
diff --git a/gcc/params.opt b/gcc/params.opt
index 2329d150ef0..b2ec436546c 100644
--- a/gcc/params.opt
+++ b/gcc/params.opt
@@ -900,6 +900,11 @@ Common Joined UInteger Var(param_ranger_logical_depth) Init(6) IntegerRange(1, 9
Maximum depth of logical expression evaluation ranger will look through when
evaluating outgoing edge ranges.
+-param=ranger-recompute-depth=
+Common Joined UInteger Var(param_ranger_recompute_depth) Init(5) IntegerRange(1, 100) Param Optimization
+Maximum depth of instruction chains to consider for recomputation in the
+outgoing range calculator.
+
-param=relation-block-limit=
Common Joined UInteger Var(param_relation_block_limit) Init(200) IntegerRange(0, 9999) Param Optimization
Maximum number of relations the oracle will register in a basic block.
