Re: [PATCH] PR tree-optimization/108359 - Utilize op1 == op2 when invoking range-ops folding.

[Andrew MacLeod <amacleod@redhat.com>]

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On 1/13/23 16:54, Jakub Jelinek wrote:
> On Fri, Jan 13, 2023 at 04:23:20PM -0500, Andrew MacLeod via Gcc-patches wrote:
>> fold_range() already invokes wi_fold_in_parts to try to get more refined
>> information. If the subranges are quite small, it will do each individual
>> calculation and combine the results.
>>
>> x * y with x = [1,3] and y = [1,3]  is broken down and we calculate each
>> possibility and we end up with [1,4][6,6][9,9] instead of [1,9]
>>
>> We limit this as the time is between quadratic to exponential depending on
>> the number of elements in x and y.
>>
>> If we also check the relation and determine that x == y, we don't need to
>> worry about that growth as this process is linear.  The above case will be
>> broken down to just  1*1, 2*2 and 3*3, resulting in a range of [1,
>> 1][4,4][9,9].
>>
>>   In the testcase, it happens to be the right_shift operation, but this
>> solution is generic and applies to all range-op operations. I added a
>> testcase which checks >>, *, + and %.
>>
>> I also arbitrarily chose 8 elements as the limit for breaking down
>> individual operations.  The overall compile time change for this is
>> negligible.
>>
>> Although this is a regression fix, it will affect all operations where x ==
>> y, which is where my initial hesitancy arose.
>>
>> Regardless, bootstrapped on x86_64-pc-linux-gnu with no regressions.  OK for
>> trunk?
> Will defer to Aldy, just some nits.
Did you mean Richi?
>
>> +  // if there are 1 to 8 values in the LH range, split them up.
>> +  r.set_undefined ();
>> +  if (lh_range >= 0 && lh_range <= 7)
>> +    {
>> +      unsigned x;
>> +      for (x = 0; x <= lh_range; x++)
> Nothing uses x after the loop, so why not
>        for (unsigned x = 0; x <= lh_range; x++)
> instead?

Just old habits.


>> @@ -234,6 +264,26 @@ range_operator::fold_range (irange &r, tree type,
>>     unsigned num_lh = lh.num_pairs ();
>>     unsigned num_rh = rh.num_pairs ();
>>   
>> +  // If op1 and op2 are equivalences, then we don't need a complete cross
>> +  // product, just pairs of matching elements.
>> +  if (relation_equiv_p (rel) && (lh == rh))
> The ()s around lh == rh look superfluous to me.
Yeah I just found it marginally more readable, but it is superfluous
>> +    {
>> +      int_range_max tmp;
>> +      r.set_undefined ();
>> +      for (unsigned x = 0; x < num_lh; ++x)
> fold_range has an upper bound of num_lh * num_rh > 12, shouldn't something
> like that be there for this case too?
> I mean, every wi_fold_in_parts_equiv can result in 8 subranges,
> but num_lh could be up to 255 here, it is true it is linear and union_
> should merge excess ones, but still I wonder if some larger num_lh upper
> bound like 20 or 32 wouldn't be useful.  Up to you...
fold_range has the num_lh * num_rh limit because it was 
quadratic/exponential and changes rapidly. Since this was linear based 
on the number of sub ranges I didn't think it would matter much, but 
sure, we can put a similar limit on it.. 16 seems reasonable.
>> +	{
>> +	  wide_int lh_lb = lh.lower_bound (x);
>> +	  wide_int lh_ub = lh.upper_bound (x);
>> +	  wi_fold_in_parts_equiv (tmp, type, lh_lb, lh_ub);
>> +	  r.union_ (tmp);
>> +	  if (r.varying_p ())
>> +	    break;
>> +	}
>> +      op1_op2_relation_effect (r, type, lh, rh, rel);
>> +      update_known_bitmask (r, m_code, lh, rh);
>> +      return true;
>> +    }
>> +
> 	Jakub
>
Updated patch attached...  I'll run it through testing whe the current 
one is done.


Andrew

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From 42010868ff3cdbb5b9ad3484f115b7c23f9e14e7 Mon Sep 17 00:00:00 2001
From: Andrew MacLeod <amacleod@redhat.com>
Date: Wed, 11 Jan 2023 18:12:51 -0500
Subject: [PATCH 2/3] Utilize op1 == op2 when invoking range-ops folding.

If there exists an equivalence relationship between op1 and op2,
any binary operation can be broken into individual operations and
unioned if there are sufficently few elements in the set.

	PR tree-optimization/108359
	gcc/
	* range-op.cc (range_operator::wi_fold_in_parts_equiv): New.
	(range_operator::fold_range): If op1 is equivalent to op2 then
	invoke new fold_in_parts_equiv to operate on sub-components.
	* range-op.h (wi_fold_in_parts_equiv): New prototype.

	gcc/testsuite/
	* gcc.dg/pr108359.c: New.
---
 gcc/range-op.cc                 | 49 ++++++++++++++++++++++++++++++++
 gcc/range-op.h                  |  5 ++++
 gcc/testsuite/gcc.dg/pr108359.c | 50 +++++++++++++++++++++++++++++++++
 3 files changed, 104 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/pr108359.c

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index ec75e07bc8a..33bc4dcb4b4 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -160,6 +160,35 @@ range_operator::wi_fold (irange &r, tree type,
   r.set_varying (type);
 }
 
+// Call wi_fold when both op1 and op2 are equivalent. Further split small
+// subranges into constants.  This can provide better precision.
+// For x + y,  when x == y with a range of [0,4] instead of [0, 8] produce
+// [0,0][2, 2][4,4][6, 6][8, 8]
+
+void
+range_operator::wi_fold_in_parts_equiv (irange &r, tree type,
+					const wide_int &lh_lb,
+					const wide_int &lh_ub) const
+{
+  int_range_max tmp;
+  widest_int lh_range = wi::sub (widest_int::from (lh_ub, TYPE_SIGN (type)),
+				 widest_int::from (lh_lb, TYPE_SIGN (type)));
+  // if there are 1 to 8 values in the LH range, split them up.
+  r.set_undefined ();
+  if (lh_range >= 0 && lh_range <= 7)
+    {
+      for (unsigned x = 0; x <= lh_range; x++)
+	{
+	  wide_int val = lh_lb + x;
+	  wi_fold (tmp, type, val, val, val, val);
+	  r.union_ (tmp);
+	}
+    }
+  // Otherwise just call wi_fold.
+  else
+    wi_fold (r, type, lh_lb, lh_ub, lh_lb, lh_ub);
+}
+
 // Call wi_fold, except further split small subranges into constants.
 // This can provide better precision. For something   8 >> [0,1]
 // Instead of [8, 16], we will produce [8,8][16,16]
@@ -234,6 +263,26 @@ range_operator::fold_range (irange &r, tree type,
   unsigned num_lh = lh.num_pairs ();
   unsigned num_rh = rh.num_pairs ();
 
+  // If op1 and op2 are equivalences, then we don't need a complete cross
+  // product, just pairs of matching elements.
+  if (relation_equiv_p (rel) && lh == rh && num_lh <= 16)
+    {
+      int_range_max tmp;
+      r.set_undefined ();
+      for (unsigned x = 0; x < num_lh; ++x)
+	{
+	  wide_int lh_lb = lh.lower_bound (x);
+	  wide_int lh_ub = lh.upper_bound (x);
+	  wi_fold_in_parts_equiv (tmp, type, lh_lb, lh_ub);
+	  r.union_ (tmp);
+	  if (r.varying_p ())
+	    break;
+	}
+      op1_op2_relation_effect (r, type, lh, rh, rel);
+      update_known_bitmask (r, m_code, lh, rh);
+      return true;
+    }
+
   // If both ranges are single pairs, fold directly into the result range.
   // If the number of subranges grows too high, produce a summary result as the
   // loop becomes exponential with little benefit.  See PR 103821.
diff --git a/gcc/range-op.h b/gcc/range-op.h
index b7b8a3b9473..998aeedb0d9 100644
--- a/gcc/range-op.h
+++ b/gcc/range-op.h
@@ -109,6 +109,11 @@ protected:
 			 const wide_int &rh_lb,
 			 const wide_int &rh_ub) const;
 
+  // Called by fold range to split small subranges into parts when op1 == op2
+  void wi_fold_in_parts_equiv (irange &r, tree type,
+			       const wide_int &lb,
+			       const wide_int &ub) const;
+
   // Tree code of the range operator or ERROR_MARK if unknown.
   tree_code m_code;
 };
diff --git a/gcc/testsuite/gcc.dg/pr108359.c b/gcc/testsuite/gcc.dg/pr108359.c
new file mode 100644
index 00000000000..00fd2de6dc7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr108359.c
@@ -0,0 +1,50 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+/* PR test case.  */
+int b = 10;
+int c;
+char e;
+void foo();
+static char(a)(char f, char g) { return f && g == 1 ? 0 : f % g; }
+short(d)(short f, short g) { return f * g; }
+int main() {
+  short h;
+  int i;
+  unsigned j;
+  h = d(b && c, 5);
+  j = h;
+  i = a(h, 237);
+  unsigned k = i;
+  e = i < 0 || k >= 32 ? 0 : i >> k;
+  if (e) {
+    c = 0;
+    foo();
+  }
+}
+
+
+/* Also Check that small ranges are broken down and optimized properly
+   in the egneric case. This function should always return 0.  */
+
+int otherfunc (int x, int z) {
+  if (x < 0 || x > 6 )
+    return 0;
+
+  if (x == z)
+    {
+    if (x >> z > 0)
+      return 1;
+    if (x * z > 26 && x * z < 35)
+      return 1;
+    if (x + z == 5)
+      return 1;
+    if ((x + z) % 2 == 1)
+      return 1;
+    }
+  return 0;
+}
+
+
+/* { dg-final { scan-tree-dump-not "foo" "optimized" } } */
+/* { dg-final { scan-tree-dump-not "return 1" "optimized" } } */
-- 
2.38.1