[PATCH] Optimize x < 0 ? ~y : y to (x >> 31) ^ y in match.pd

[PATCH] Optimize x < 0 ? ~y : y to (x >> 31) ^ y in match.pd

[apinski]

From: Andrew Pinski <apinski@marvell.com>

This copies the optimization that is done in phiopt for
"x < 0 ? ~y : y to (x >> 31) ^ y" into match.pd. The code
for phiopt is kept around until phiopt uses match.pd (which
I am working towards).

Note the original testcase is now optimized early on and I added a
new testcase to optimize during phiopt.

OK?  Bootstrapped and tested on x86_64-linux-gnu with no regressions.

Thanks,
Andrew Pinski

gcc:
	* match.pd (x < 0 ? ~y : y): New patterns.

gcc/testsuite:
	* gcc.dg/tree-ssa/pr96928.c: Update test for slightly different IR.
	* gcc.dg/tree-ssa/pr96928-1.c: New testcase.
---
 gcc/match.pd                              | 30 +++++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c | 48 +++++++++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr96928.c   |  7 +++--
 3 files changed, 83 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c

diff --git a/gcc/match.pd b/gcc/match.pd
index ad6b057..6710aa9 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -4875,6 +4875,36 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (cmp (bit_and@2 @0 integer_pow2p@1) @1)
   (icmp @2 { build_zero_cst (TREE_TYPE (@0)); })))
 
+(for cmp (ge lt)
+/* x < 0 ? ~y : y into (x >> (prec-1)) ^ y. */
+/* x >= 0 ? ~y : y into ~((x >> (prec-1)) ^ y). */
+ (simplify
+  (cond (cmp @0 integer_zerop) (bit_not @1) @1)
+   (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
+        && !TYPE_UNSIGNED (TREE_TYPE (@0))
+        && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (type))
+    (with
+     {
+       tree shifter = build_int_cst (integer_type_node, TYPE_PRECISION (type) - 1);
+     }
+    (if (cmp == LT_EXPR)
+     (bit_xor (convert (rshift @0 {shifter;})) @1)
+     (bit_not (bit_xor (convert (rshift @0 {shifter;})) @1))))))
+/* x < 0 ? y : ~y into ~((x >> (prec-1)) ^ y). */
+/* x >= 0 ? y : ~y into (x >> (prec-1)) ^ y. */
+ (simplify
+  (cond (cmp @0 integer_zerop) @1 (bit_not @1))
+   (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
+        && !TYPE_UNSIGNED (TREE_TYPE (@0))
+        && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (type))
+    (with
+     {
+       tree shifter = build_int_cst (integer_type_node, TYPE_PRECISION (type) - 1);
+     }
+    (if (cmp == GE_EXPR)
+     (bit_xor (convert (rshift @0 {shifter;})) @1)
+     (bit_not (bit_xor (convert (rshift @0 {shifter;})) @1)))))))
+
 /* If we have (A & C) != 0 ? D : 0 where C and D are powers of 2,
    convert this into a shift followed by ANDing with D.  */
 (simplify
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
new file mode 100644
index 0000000..a2770e5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
@@ -0,0 +1,48 @@
+/* PR tree-optimization/96928 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-phiopt2" } */
+/* { dg-final { scan-tree-dump-times " = a_\[0-9]*\\\(D\\\) >> " 5 "phiopt2" } } */
+/* { dg-final { scan-tree-dump-times " = ~c_\[0-9]*\\\(D\\\);" 1 "phiopt2" } } */
+/* { dg-final { scan-tree-dump-times " = ~" 1 "phiopt2" } } */
+/* { dg-final { scan-tree-dump-times " = \[abc_0-9\\\(\\\)D]* \\\^ " 5 "phiopt2" } } */
+/* { dg-final { scan-tree-dump-not "a < 0" "phiopt2" } } */
+
+int
+foo (int a)
+{
+  if (a < 0)
+    return ~a;
+  return a;
+}
+
+int
+bar (int a, int b)
+{
+  if (a < 0)
+    return ~b;
+  return b;
+}
+
+unsigned
+baz (int a, unsigned int b)
+{
+  if (a < 0)
+    return ~b;
+  return b;
+}
+
+unsigned
+qux (int a, unsigned int c)
+{
+  if (a >= 0)
+    return ~c;
+  return c;
+}
+
+int
+corge (int a, int b)
+{
+  if (a >= 0)
+    return b;
+  return ~b;
+}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96928.c b/gcc/testsuite/gcc.dg/tree-ssa/pr96928.c
index 2091357..e8fd82f 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr96928.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96928.c
@@ -1,8 +1,11 @@
 /* PR tree-optimization/96928 */
 /* { dg-do compile } */
-/* { dg-options "-O2 -fdump-tree-phiopt2" } */
+/* { dg-options "-O2 -fdump-tree-phiopt2 -fdump-tree-optimized" } */
 /* { dg-final { scan-tree-dump-times " = a_\[0-9]*\\\(D\\\) >> " 5 "phiopt2" } } */
-/* { dg-final { scan-tree-dump-times " = ~c_\[0-9]*\\\(D\\\);" 1 "phiopt2" } } */
+/* The following check is done at optimized because a ^ (~b) is rewritten as ~(a^b)
+   and in the case of match.pd optimizing these ?:, the ~ is moved out already
+   by the time we get to phiopt2. */
+/* { dg-final { scan-tree-dump-times "\\\^ c_\[0-9]*\\\(D\\\);" 1 "optimized" } } */
 /* { dg-final { scan-tree-dump-times " = ~" 1 "phiopt2" } } */
 /* { dg-final { scan-tree-dump-times " = \[abc_0-9\\\(\\\)D]* \\\^ " 5 "phiopt2" } } */
 /* { dg-final { scan-tree-dump-not "a < 0" "phiopt2" } } */
-- 
1.8.3.1

Re: [PATCH] Optimize x < 0 ? ~y : y to (x >> 31) ^ y in match.pd

[Martin Liška]

Hello.

Similarly to:
https://gcc.gnu.org/pipermail/gcc-patches/2021-May/571039.html

I've just reverted the ChangeLog commit change. I'm planning update
of the documentation.

Cheers,
Martin

Re: [PATCH] Optimize x < 0 ? ~y : y to (x >> 31) ^ y in match.pd

[Marc Glisse]

On Sun, 23 May 2021, apinski--- via Gcc-patches wrote:

> +(for cmp (ge lt)
> +/* x < 0 ? ~y : y into (x >> (prec-1)) ^ y. */
> +/* x >= 0 ? ~y : y into ~((x >> (prec-1)) ^ y). */
> + (simplify
> +  (cond (cmp @0 integer_zerop) (bit_not @1) @1)
> +   (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
> +        && !TYPE_UNSIGNED (TREE_TYPE (@0))
> +        && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (type))

Is there a risk that x is signed char (precision 8) and y is a vector with 
8 elements?

-- 
Marc Glisse

Re: [PATCH] Optimize x < 0 ? ~y : y to (x >> 31) ^ y in match.pd

[Andrew Pinski]

On Sun, May 23, 2021 at 6:14 AM Marc Glisse <marc.glisse@inria.fr> wrote:
>
> On Sun, 23 May 2021, apinski--- via Gcc-patches wrote:
>
> > +(for cmp (ge lt)
> > +/* x < 0 ? ~y : y into (x >> (prec-1)) ^ y. */
> > +/* x >= 0 ? ~y : y into ~((x >> (prec-1)) ^ y). */
> > + (simplify
> > +  (cond (cmp @0 integer_zerop) (bit_not @1) @1)
> > +   (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
> > +        && !TYPE_UNSIGNED (TREE_TYPE (@0))
> > +        && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (type))
>
> Is there a risk that x is signed char (precision 8) and y is a vector with
> 8 elements?

Yes there should be a check for "INTEGRAL_TYPE_P (type)" there too.  I
had missed it when I was doing the conversion.  I will add it and
resubmit the patch.

Thanks,
Andrew

>
> --
> Marc Glisse

Re: [PATCH] Optimize x < 0 ? ~y : y to (x >> 31) ^ y in match.pd

[Andrew Pinski]

On Sun, May 23, 2021 at 5:49 AM Martin Liška <mliska@suse.cz> wrote:
>
> Hello.
>
> Similarly to:
> https://gcc.gnu.org/pipermail/gcc-patches/2021-May/571039.html
>
> I've just reverted the ChangeLog commit change. I'm planning update
> of the documentation.

Obviously is for the other patch which I pushed and not for this one.
I was trying to figure out why I could not push my changes with the
changelog included, the error message was not so obvious either.

Thanks,
Andrew

>
> Cheers,
> Martin

Re: [PATCH] Optimize x < 0 ? ~y : y to (x >> 31) ^ y in match.pd

[Jeff Law]

On 5/23/2021 10:21 AM, Andrew Pinski via Gcc-patches wrote:
> On Sun, May 23, 2021 at 6:14 AM Marc Glisse <marc.glisse@inria.fr> wrote:
>> On Sun, 23 May 2021, apinski--- via Gcc-patches wrote:
>>
>>> +(for cmp (ge lt)
>>> +/* x < 0 ? ~y : y into (x >> (prec-1)) ^ y. */
>>> +/* x >= 0 ? ~y : y into ~((x >> (prec-1)) ^ y). */
>>> + (simplify
>>> +  (cond (cmp @0 integer_zerop) (bit_not @1) @1)
>>> +   (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
>>> +        && !TYPE_UNSIGNED (TREE_TYPE (@0))
>>> +        && TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (type))
>> Is there a risk that x is signed char (precision 8) and y is a vector with
>> 8 elements?
> Yes there should be a check for "INTEGRAL_TYPE_P (type)" there too.  I
> had missed it when I was doing the conversion.  I will add it and
> resubmit the patch.
Consider it approved with that fix.

Thanks,
Jeff