From: Jakub Jelinek <jakub@redhat.com>
Date: Wed, 6 May 2020 09:20:20 +0000 (+0200)
Subject: match.pd: Optimize ~(~X +- Y) into (X -+ Y) [PR94921]
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=a7b76d574b19190da190a60c065f347f40bab59e;p=gcc.git

match.pd: Optimize ~(~X +- Y) into (X -+ Y) [PR94921]

According to my verification proglet, this transformation for signed types
with undefined overflow doesn't introduce nor remove any UB cases, so should
be valid even for signed integral types.
Not using a for because of the :c on plus which can't be there on minus.

2020-05-06  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/94921
	* match.pd (~(~X - Y) -> X + Y, ~(~X + Y) -> X - Y): New
	simplifications.

	* gcc.dg/tree-ssa/pr94921.c: New test.
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e0dd54cdfe7..8bb28935555 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2020-05-06  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/94921
+	* match.pd (~(~X - Y) -> X + Y, ~(~X + Y) -> X - Y): New
+	simplifications.
+
 2020-05-06  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/94965
diff --git a/gcc/match.pd b/gcc/match.pd
index d9575179655..9259dd4ddaa 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1010,6 +1010,14 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   @0))
 #endif
 
+/* ~(~X - Y) -> X + Y and ~(~X + Y) -> X - Y.  */
+(simplify
+ (bit_not (minus (bit_not @0) @1))
+ (plus @0 @1))
+(simplify
+ (bit_not (plus:c (bit_not @0) @1))
+ (minus @0 @1))
+
 /* x + (x & 1) -> (x + 1) & ~1 */
 (simplify
  (plus:c @0 (bit_and:s @0 integer_onep@1))
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 1f01ff0b886..a66a01244f9 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 2020-05-06  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/94921
+	* match.pd (~(~X - Y) -> X + Y, ~(~X + Y) -> X - Y): New
+	simplifications.
+
 	PR rtl-optimization/94873
 	* gcc.dg/pr94873.c: New test.
 
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr94921.c b/gcc/testsuite/gcc.dg/tree-ssa/pr94921.c
new file mode 100644
index 00000000000..2c752caae07
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr94921.c
@@ -0,0 +1,18 @@
+/* PR tree-optimization/94921 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump " \[ab]_\[0-9]+\\\(D\\\) \\+ \[ab]_\[0-9]+\\\(D\\\);" "optimized" } } */
+/* { dg-final { scan-tree-dump " c_\[0-9]+\\\(D\\\) - d_\[0-9]+\\\(D\\\);" "optimized" } } */
+/* { dg-final { scan-tree-dump-not " ~\[abcd]\?_\[0-9]\+" "optimized" } } */
+
+int
+foo (int a, int b)
+{
+  return ~(~a - b);
+}
+
+int
+bar (int c, int d)
+{
+  return ~(~c + d);
+}