Re: [Patch] PR67351 Implement << N & >> N optimizers

["Hurugalawadi, Naveen" <Naveen.Hurugalawadi@caviumnetworks.com>]

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Hi,

Thanks for all the review and comments.

>> replace the precision test with wi::ltu_p (@1, TYPE_PRECISION (type)
>> use element_precision instead of TYPE_PRECISION

Please find attached the modified patch as per review comments.

Please review the same and let me know if the patch is okay?

Regression Tested on AArch64 and X86_64.

Thanks,
Naveen

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diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index d478c4d..a79bfa7 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -10412,32 +10412,6 @@ fold_binary_loc (location_t loc,
 
       prec = element_precision (type);
 
-      /* Transform (x >> c) << c into x & (-1<<c), or transform (x << c) >> c
-         into x & ((unsigned)-1 >> c) for unsigned types.  */
-      if (((code == LSHIFT_EXPR && TREE_CODE (arg0) == RSHIFT_EXPR)
-           || (TYPE_UNSIGNED (type)
-	       && code == RSHIFT_EXPR && TREE_CODE (arg0) == LSHIFT_EXPR))
-	  && tree_fits_uhwi_p (arg1)
-	  && tree_to_uhwi (arg1) < prec
-	  && tree_fits_uhwi_p (TREE_OPERAND (arg0, 1))
-	  && tree_to_uhwi (TREE_OPERAND (arg0, 1)) < prec)
-	{
-	  HOST_WIDE_INT low0 = tree_to_uhwi (TREE_OPERAND (arg0, 1));
-	  HOST_WIDE_INT low1 = tree_to_uhwi (arg1);
-	  tree lshift;
-	  tree arg00;
-
-	  if (low0 == low1)
-	    {
-	      arg00 = fold_convert_loc (loc, type, TREE_OPERAND (arg0, 0));
-
-	      lshift = build_minus_one_cst (type);
-	      lshift = const_binop (code, lshift, arg1);
-
-	      return fold_build2_loc (loc, BIT_AND_EXPR, type, arg00, lshift);
-	    }
-	}
-
       /* If we have a rotate of a bit operation with the rotate count and
 	 the second operand of the bit operation both constant,
 	 permute the two operations.  */
diff --git a/gcc/match.pd b/gcc/match.pd
index fb4b342..181a389 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -931,6 +931,22 @@ along with GCC; see the file COPYING3.  If not see
       && tree_expr_nonnegative_p (@1))
   @0))
 
+/* Optimize (x >> c) << c into x & (-1<<c).  */
+(simplify
+ (lshift (rshift @0 INTEGER_CST@1) @1)
+ (if (tree_fits_uhwi_p (@1)
+      && wi::ltu_p (@1, element_precision (type)))
+  (bit_and @0 (lshift { build_minus_one_cst (type); } @1))))
+
+/* Optimize (x << c) >> c into x & ((unsigned)-1 >> c) for unsigned
+   types.  */
+(simplify
+ (rshift (lshift @0 INTEGER_CST@1) @1)
+ (if (TYPE_UNSIGNED (type)
+      && tree_fits_uhwi_p (@1)
+      && (wi::ltu_p (@1, element_precision (type))))
+  (bit_and @0 (rshift { build_minus_one_cst (type); } @1))))
+
 (for shiftrotate (lrotate rrotate lshift rshift)
  (simplify
   (shiftrotate @0 integer_zerop)
diff --git a/gcc/testsuite/g++.dg/pr67351.C b/gcc/testsuite/g++.dg/pr67351.C
new file mode 100644
index 0000000..c86c920
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr67351.C
@@ -0,0 +1,106 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+typedef unsigned char uchar;
+typedef unsigned short ushort;
+typedef unsigned int uint;
+typedef unsigned long long uint64;
+
+class MyRgba
+{
+  uint rgba;
+
+public:
+    explicit MyRgba (uint c):rgba (c)
+  {
+  };
+
+  static MyRgba fromRgba (uchar r, uchar g, uchar b, uchar a)
+  {
+    return MyRgba (uint (r) << 24
+		   | uint (g) << 16 | uint (b) << 8 | uint (a));
+  }
+
+  uchar r ()
+  {
+    return rgba >> 24;
+  }
+  uchar g ()
+  {
+    return rgba >> 16;
+  }
+  uchar b ()
+  {
+    return rgba >> 8;
+  }
+  uchar a ()
+  {
+    return rgba;
+  }
+
+  void setG (uchar _g)
+  {
+    *this = fromRgba (r (), _g, b (), a ());
+  }
+};
+
+extern MyRgba giveMe ();
+
+MyRgba
+test ()
+{
+  MyRgba a = giveMe ();
+  a.setG (0xf0);
+  return a;
+}
+
+class MyRgba64
+{
+  uint64 rgba;
+
+public:
+    explicit MyRgba64 (uint64 c):rgba (c)
+  {
+  };
+
+  static MyRgba64 fromRgba64 (ushort r, ushort g, ushort b, ushort a)
+  {
+    return MyRgba64 (uint64 (r) << 48
+		     | uint64 (g) << 32 | uint64 (b) << 16 | uint64 (a));
+  }
+
+  ushort r ()
+  {
+    return rgba >> 48;
+  }
+  ushort g ()
+  {
+    return rgba >> 32;
+  }
+  ushort b ()
+  {
+    return rgba >> 16;
+  }
+  ushort a ()
+  {
+    return rgba;
+  }
+
+  void setG (ushort _g)
+  {
+    *this = fromRgba64 (r (), _g, b (), a ());
+  }
+};
+
+extern MyRgba64 giveMe64 ();
+
+MyRgba64
+test64 ()
+{
+  MyRgba64 a = giveMe64 ();
+  a.setG (0xf0f0);
+  return a;
+}
+
+/* { dg-final { scan-assembler-not "<<" } } */
+/* { dg-final { scan-assembler-not ">>" } } */