[match.pd] Fix for PR35691

[Prathamesh Kulkarni]

On 4 November 2016 at 13:41, Richard Biener <rguenther@suse.de> wrote:
> On Thu, 3 Nov 2016, Marc Glisse wrote:
>
>> On Thu, 3 Nov 2016, Richard Biener wrote:
>>
>> > > > > The transform would also work for vectors (element_precision for
>> > > > > the test but also a value-matching zero which should ensure the
>> > > > > same number of elements).
>> > > > Um sorry, I didn't get how to check vectors to be of equal length by a
>> > > > matching zero.
>> > > > Could you please elaborate on that ?
>> > >
>> > > He may have meant something like:
>> > >
>> > >   (op (cmp @0 integer_zerop@2) (cmp @1 @2))
>> >
>> > I meant with one being @@2 to allow signed vs. Unsigned @0/@1 which was the
>> > point of the pattern.
>>
>> Oups, that's what I had written first, and then I somehow managed to confuse
>> myself enough to remove it so as to remove the call to types_match :-(
>>
>> > > So the last operand is checked with operand_equal_p instead of
>> > > integer_zerop. But the fact that we could compute bit_ior on the
>> > > comparison results should already imply that the number of elements is the
>> > > same.
>> >
>> > Though for equality compares we also allow scalar results IIRC.
>>
>> Oh, right, I keep forgetting that :-( And I have no idea how to generate one
>> for a testcase, at least until the GIMPLE FE lands...
>>
>> > > On platforms that have IOR on floats (at least x86 with SSE, maybe some
>> > > vector mode on s390?), it would be cool to do the same for floats (most
>> > > likely at the RTL level).
>> >
>> > On GIMPLE view-converts could come to the rescue here as well.  Or we cab
>> > just allow bit-and/or on floats as much as we allow them on pointers.
>>
>> Would that generate sensible code on targets that do not have logic insns for
>> floats? Actually, even on x86_64 that generates inefficient code, so there
>> would be some work (for instance grep finds no gen_iordf3, only gen_iorv2df3).
>>
>> I am also a bit wary of doing those obfuscating optimizations too early...
>> a==0 is something that other optimizations might use. long
>> c=(long&)a|(long&)b; (double&)c==0; less so...
>>
>> (and I am assuming that signaling NaNs don't make the whole transformation
>> impossible, which might be wrong)
>
> Yeah.  I also think it's not so much important - I just wanted to mention
> vectors...
>
> Btw, I still think we need a more sensible infrastructure for passes
> to gather, analyze and modify complex conditions.  (I'm always pointing
> to tree-affine.c as an, albeit not very good, example for handling
> a similar problem)
Thanks for mentioning the value-matching capture @@, I wasn't aware of
this match.pd feature.
The current patch keeps it restricted to only bitwise operators on integers.
Bootstrap+test running on x86_64-unknown-linux-gnu.
OK to commit if passes ?

Thanks,
Prathamesh
>
> Richard.
-------------- next part --------------
2016-11-04  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

	PR middle-end/35691
	* match.pd: Add following two patterns:
	(x == 0 & y == 0) -> (x | typeof(x)(y)) == 0.
	(x != 0 | y != 0) -> (x | typeof(x)(y)) != 0.

testsuite/
	* gcc.dg/pr35691-1.c: New test-case.
	* gcc.dg/pr35691-2.c: Likewise.
	* gcc.dg/pr35691-3.c: Likewise.
	* gcc.dg/pr35691-4.c: Likewise.

diff --git a/gcc/match.pd b/gcc/match.pd
index 48f7351..4f74942 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -519,6 +519,19 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (if (TYPE_UNSIGNED (type))
     (bit_and @0 (bit_not (lshift { build_all_ones_cst (type); } @1)))))
 
+/* PR35691: Transform
+   (x == 0 & y == 0) -> (x | typeof(x)(y)) == 0.
+   (x != 0 | y != 0) -> (x | typeof(x)(y)) != 0.  */
+
+(for bitop (bit_and bit_ior)
+     cmp (eq ne)
+ (simplify
+  (bitop (cmp @0 integer_zerop) (cmp @1 integer_zerop))
+   (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
+       && INTEGRAL_TYPE_P (TREE_TYPE (@1))
+       && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (TREE_TYPE (@1)))
+    (cmp (bit_ior @0 (convert @1)) { build_zero_cst (TREE_TYPE (@0)); }))))
+
 /* Fold (A & ~B) - (A & B) into (A ^ B) - B.  */
 (simplify
  (minus (bit_and:cs @0 (bit_not @1)) (bit_and:cs @0 @1))
diff --git a/gcc/testsuite/gcc.dg/pr35691-1.c b/gcc/testsuite/gcc.dg/pr35691-1.c
new file mode 100644
index 0000000..5211f815
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr35691-1.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-forwprop-details" } */
+
+int foo(int z0, unsigned z1)
+{
+  int t0 = (z0 == 0);
+  int t1 = (z1 == 0);
+  int t2 = (t0 && t1);
+  return t2;
+}
+
+/* { dg-final { scan-tree-dump "gimple_simplified to _\[0-9\]* = \\(int\\) z1_\[0-9\]*\\(D\\);" "forwprop1" } } */
diff --git a/gcc/testsuite/gcc.dg/pr35691-2.c b/gcc/testsuite/gcc.dg/pr35691-2.c
new file mode 100644
index 0000000..90cbf6d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr35691-2.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-forwprop-details" } */
+
+int foo(int z0, unsigned z1)
+{
+  int t0 = (z0 != 0);
+  int t1 = (z1 != 0);
+  int t2 = (t0 || t1);
+  return t2;
+}
+
+/* { dg-final { scan-tree-dump "gimple_simplified to _\[0-9\]* = \\(int\\) z1_\[0-9\]*\\(D\\);" "forwprop1" } } */