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-Tag: misc/first-auto-changelog~490
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a7b76d574b19190da190a60c065f347f40bab59e;p=thirdparty%2Fgcc.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 e0dd54cdfe74..8bb289355550 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 d95751796551..9259dd4ddaa1 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 1f01ff0b8860..a66a01244f96 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 000000000000..2c752caae07d
--- /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);
+}