Hi!
I decided to revive this patch:
https://gcc.gnu.org/ml/gcc-patches/2015-06/msg00999.html.
I addressed review comments about sign conversions. Bootstrapped and regtested
on x86_64-linux-gnu {,-m32}. OK for trunk?
--
Regards,
Mikhail Maltsev
gcc/testsuite/ChangeLog:
2016-05-08 Mikhail Maltsev <malts...@gmail.com>
PR tree-optimization/54579
PR middle-end/55299
* gcc.dg/fold-notrotate-1.c: New test.
* gcc.dg/fold-notshift-1.c: New test.
* gcc.dg/fold-notshift-2.c: New test.
gcc/ChangeLog:
2016-05-08 Mikhail Maltsev <malts...@gmail.com>
PR tree-optimization/54579
PR middle-end/55299
* match.pd (~(~X >> Y), ~(~X >>r Y), ~(~X <<r Y)): New patterns.
diff --git a/gcc/match.pd b/gcc/match.pd
index 55dd23c..cc0d03b 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1453,6 +1453,25 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(with { tree mask = int_const_binop (shift, fold_convert (type, @2), @1); }
(bit_op (shift (convert @0) @1) { mask; }))))))
+/* ~((~X) >> Y) -> X >> Y (for arithmetic shift). */
+(simplify
+ (bit_not (convert? (rshift (bit_not @0) @1)))
+ (if (!TYPE_UNSIGNED (TREE_TYPE (@0)))
+ (convert (rshift @0 @1))))
+(simplify
+ (bit_not (convert? (rshift (convert@0 (bit_not @1)) @2)))
+ (if (!TYPE_UNSIGNED (TREE_TYPE (@0)))
+ (with
+ { tree shift_type = TREE_TYPE (@0); }
+ (convert (rshift:shift_type (convert @1) @2)))))
+
+/* Same as above, but for rotates. */
+(for rotate (lrotate rrotate)
+ (simplify
+ (bit_not (convert1? (rotate (convert2? (bit_not @0)) @1)))
+ (with
+ { tree operand_type = TREE_TYPE (@0); }
+ (convert (rotate:operand_type @0 @1)))))
/* Simplifications of conversions. */
diff --git a/gcc/testsuite/gcc.dg/fold-notrotate-1.c b/gcc/testsuite/gcc.dg/fold-notrotate-1.c
new file mode 100644
index 0000000..a9b3804
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-notrotate-1.c
@@ -0,0 +1,54 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+#define INT_BITS (sizeof (int) * __CHAR_BIT__)
+#define ROL(x, y) ((x) << (y) | (x) >> (INT_BITS - (y)))
+#define ROR(x, y) ((x) >> (y) | (x) << (INT_BITS - (y)))
+
+unsigned
+rol (unsigned a, unsigned b)
+{
+ return ~ROL (~a, b);
+}
+
+unsigned int
+ror (unsigned a, unsigned b)
+{
+ return ~ROR (~a, b);
+}
+
+int
+rol_conv1 (int a, unsigned b)
+{
+ return ~(int)ROL((unsigned)~a, b);
+}
+
+int
+rol_conv2 (int a, unsigned b)
+{
+ return ~ROL((unsigned)~a, b);
+}
+
+int
+rol_conv3 (unsigned a, unsigned b)
+{
+ return ~(int)ROL(~a, b);
+}
+
+#define LONG_BITS (sizeof (long) * __CHAR_BIT__)
+#define ROLL(x, y) ((x) << (y) | (x) >> (LONG_BITS - (y)))
+#define RORL(x, y) ((x) >> (y) | (x) << (LONG_BITS - (y)))
+
+unsigned long
+roll (unsigned long a, unsigned long b)
+{
+ return ~ROLL (~a, b);
+}
+
+unsigned long
+rorl (unsigned long a, unsigned long b)
+{
+ return ~RORL (~a, b);
+}
+
+/* { dg-final { scan-tree-dump-not "~" "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/fold-notshift-1.c b/gcc/testsuite/gcc.dg/fold-notshift-1.c
new file mode 100644
index 0000000..674f3c7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-notshift-1.c
@@ -0,0 +1,62 @@
+/* PR tree-optimization/54579
+ PR middle-end/55299 */
+
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-cddce1" } */
+
+int
+asr1 (int a, int b)
+{
+ return ~((~a) >> b);
+}
+
+long
+asr1l (long a, long b)
+{
+ return ~((~a) >> b);
+}
+
+int
+asr_conv (unsigned a, unsigned b)
+{
+ return ~((int)~a >> b);
+}
+
+unsigned
+asr_conv2 (unsigned a, unsigned b)
+{
+ return ~(unsigned)((int)~a >> b);
+}
+
+unsigned
+asr_conv3 (int a, int b)
+{
+ return ~(unsigned)(~a >> b);
+}
+
+int
+asr2 (int a, int b)
+{
+ return -((-a - 1) >> b) - 1;
+}
+
+int
+asr3 (int a, int b)
+{
+ return a < 0 ? ~((~a) >> b) : a >> b;
+}
+
+long
+asr3l (long a, int b)
+{
+ return a < 0 ? ~((~a) >> b) : a >> b;
+}
+
+int
+asr4 (int a, int b)
+{
+ return a < 0 ? -((-a - 1) >> b) - 1 : a >> b;
+}
+
+/* { dg-final { scan-tree-dump-times ">>" 9 "cddce1" } } */
+/* { dg-final { scan-tree-dump-not "~" "cddce1" } } */
diff --git a/gcc/testsuite/gcc.dg/fold-notshift-2.c b/gcc/testsuite/gcc.dg/fold-notshift-2.c
new file mode 100644
index 0000000..5287610
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-notshift-2.c
@@ -0,0 +1,18 @@
+/* PR middle-end/55299 */
+
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-cddce1" } */
+
+unsigned int
+lsr (unsigned int a, unsigned int b)
+{
+ return ~((~a) >> b);
+}
+
+int
+sl (int a, int b)
+{
+ return ~((~a) << b);
+}
+
+/* { dg-final { scan-tree-dump-times "~" 4 "cddce1" } } */
