Re: [PATCH, GCC] PR middle-end/55299, fold bitnot through ASR and rotates

[Mikhail Maltsev <maltsevm at gmail dot com>]

On 05/08/2016 10:57 PM, Marc Glisse wrote:
> On Sun, 8 May 2016, Mikhail Maltsev wrote:
> 
>> 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?
> 
> Hello,
> 
> are you sure that your transformations are safe for any kind of conversion?
> 
Oops, indeed, only narrowing conversions should be allowed. I updated the patch
and added some more test cases.

-- 
Regards,
    Mikhail Maltsev

diff --git a/gcc/match.pd b/gcc/match.pd
index 55dd23c..b545cc7 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1453,6 +1453,31 @@ 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))
+       && TYPE_PRECISION (type) <= TYPE_PRECISION (TREE_TYPE (@0)))
+   (convert (rshift @0 @1))))
+
+(simplify
+ (bit_not (convert? (rshift (convert@0 (bit_not @1)) @2)))
+  (if (!TYPE_UNSIGNED (TREE_TYPE (@0))
+       && TYPE_PRECISION (TREE_TYPE (@0)) <= TYPE_PRECISION (TREE_TYPE (@1))
+       && TYPE_PRECISION (type) <= TYPE_PRECISION (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?@0 (rotate (convert2?@1 (bit_not @2)) @3)))
+   (if (TYPE_PRECISION (TREE_TYPE (@1)) <= TYPE_PRECISION (TREE_TYPE (@2))
+        && TYPE_PRECISION (TREE_TYPE (@0)) <= TYPE_PRECISION (TREE_TYPE (@1)))
+    (with
+     { tree operand_type = TREE_TYPE (@2); }
+      (convert (rotate:operand_type @2 @3))))))
 
 /* 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..2de236f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-notshift-1.c
@@ -0,0 +1,77 @@
+/* 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);
+}
+
+typedef __INT32_TYPE__ int32_t;
+typedef __INT64_TYPE__ int64_t;
+
+int32_t
+asr_conv4 (int64_t a, int b)
+{
+  return ~((int32_t)~a >> b);
+}
+
+int32_t
+asr_conv5 (int64_t a, int b)
+{
+  return ~(int32_t)(~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;
+}
+
+int64_t
+asr3l (int64_t 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 ">>" 11 "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..32635f1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-notshift-2.c
@@ -0,0 +1,33 @@
+/* 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);
+}
+
+typedef __INT32_TYPE__ int32_t;
+typedef __INT64_TYPE__ int64_t;
+
+int64_t
+asr_widen1 (int32_t a, int b)
+{
+  return ~((int64_t)(~a) >> b);
+}
+
+int64_t
+asr_widen2 (int32_t a, int b)
+{
+  return ~(int64_t)(~a >> b);
+}
+
+/* { dg-final { scan-tree-dump-times "~" 8 "cddce1" } } */