Re: recomputation and PR 109154

[Andrew MacLeod <amacleod@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 1021 bytes --]


On 3/30/23 09:41, Jakub Jelinek wrote:
> On Wed, Mar 29, 2023 at 01:22:27PM -0400, Andrew MacLeod wrote:
>> 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)
> Our middle-end warnings are just badly designed :(, the better value ranges
> are, the more false positives they have.
>
>> commit 358d0ca44faf2e20fbacd0f74386308b5ca52cd4
>> Author: Andrew MacLeod <amacleod@redhat.com>
>> Date:   Tue Mar 28 12:16:34 2023 -0400
>>
>>      Add recursive GORI recompuations with a depth limit.
> LGTM for trunk, let's do with the regression incrementally.
> Or as Richard mentioned on IRC, one possibility would be to force this
> param temporarily to 1 (or whatever matches previous behavior) for the
> diagnostic range queries).
>
> You need a ChangeLog entry though...
>
Attached. I also removed the bogus warning in Walloc-13.c that no longer 
happens

So incrementally deal with it.. what? just let it fail?

Andrew

[-- Attachment #2: 154.diff --]
[-- Type: text/x-patch, Size: 4520 bytes --]

commit debb8ce1f9b9d5a72d88d0ae90a6b4da5130ff59
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Tue Mar 28 12:16:34 2023 -0400

    Add recursive GORI recompuations with a depth limit.
    
            PR tree-optimization/109154
            gcc/
            * gimple-range-gori.cc (gori_compute::may_recompute_p): Add depth limit.
            * gimple-range-gori.h (may_recompute_p): Add depth param.
            * params.opt (ranger-recompute-depth): New param.
    
            gcc/testsuite/
            * gcc.dg/Walloca-13.c: Remove bogus warning that is now fixed.

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.
diff --git a/gcc/testsuite/gcc.dg/Walloca-13.c b/gcc/testsuite/gcc.dg/Walloca-13.c
index 99d62065e26..d3af0c50399 100644
--- a/gcc/testsuite/gcc.dg/Walloca-13.c
+++ b/gcc/testsuite/gcc.dg/Walloca-13.c
@@ -8,5 +8,5 @@ void g (int *p, int *q)
 {
   __SIZE_TYPE__ n = (__SIZE_TYPE__)(p - q);
   if (n < 100)
-    f (__builtin_alloca (n)); // { dg-bogus "may be too large" "" { xfail { *-*-* } } }
+    f (__builtin_alloca (n));
 }