match.pd: Optimize ffs comparisons against constants [PR95527]

The following patch implements various optimizations of __builtin_ffs*
against constants.

2020-06-09  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/95527
	* match.pd (__builtin_ffs (X) cmp CST): New optimizations.

	* gcc.dg/tree-ssa/pr95527.c: New test.

diff --git a/gcc/match.pd b/gcc/match.pd
index 2b8c37e690e88b88408a4655262ef1a38e2ee53f..53ced346bbd2f96ad437c6fd2232b593d0a3d2d2 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -6024,6 +6024,54 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (plus (CTZ:type @0) { build_one_cst (type); })))
 #endif
 
+(for ffs (BUILT_IN_FFS BUILT_IN_FFSL BUILT_IN_FFSLL
+         BUILT_IN_FFSIMAX)
+ /* __builtin_ffs (X) == 0 -> X == 0.
+    __builtin_ffs (X) == 6 -> (X & 63) == 32.  */
+ (for cmp (eq ne)
+  (simplify
+   (cmp (ffs@2 @0) INTEGER_CST@1)
+    (with { int prec = TYPE_PRECISION (TREE_TYPE (@0)); }
+     (switch
+      (if (integer_zerop (@1))
+       (cmp @0 { build_zero_cst (TREE_TYPE (@0)); }))
+      (if (tree_int_cst_sgn (@1) < 0 || wi::to_widest (@1) > prec)
+       { constant_boolean_node (cmp == NE_EXPR ? true : false, type); })
+      (if (single_use (@2))
+       (cmp (bit_and @0 { wide_int_to_tree (TREE_TYPE (@0),
+                                           wi::mask (tree_to_uhwi (@1),
+                                                     false, prec)); })
+           { wide_int_to_tree (TREE_TYPE (@0),
+                               wi::shifted_mask (tree_to_uhwi (@1) - 1, 1,
+                                                 false, prec)); }))))))
+
+ /* __builtin_ffs (X) > 6 -> X != 0 && (X & 63) == 0.  */
+ (for cmp (gt le)
+      cmp2 (ne eq)
+      cmp3 (eq ne)
+      bit_op (bit_and bit_ior)
+  (simplify
+   (cmp (ffs@2 @0) INTEGER_CST@1)
+    (with { int prec = TYPE_PRECISION (TREE_TYPE (@0)); }
+     (switch
+      (if (integer_zerop (@1))
+       (cmp2 @0 { build_zero_cst (TREE_TYPE (@0)); }))
+      (if (tree_int_cst_sgn (@1) < 0)
+       { constant_boolean_node (cmp == GT_EXPR ? true : false, type); })
+      (if (wi::to_widest (@1) >= prec)
+       { constant_boolean_node (cmp == GT_EXPR ? false : true, type); })
+      (if (wi::to_widest (@1) == prec - 1)
+       (cmp3 @0 { wide_int_to_tree (TREE_TYPE (@0),
+                                   wi::shifted_mask (prec - 1, 1,
+                                                     false, prec)); }))
+      (if (single_use (@2))
+       (bit_op (cmp2 @0 { build_zero_cst (TREE_TYPE (@0)); })
+              (cmp3 (bit_and @0
+                             { wide_int_to_tree (TREE_TYPE (@0),
+                                                 wi::mask (tree_to_uhwi (@1),
+                                                 false, prec)); })
+                    { build_zero_cst (TREE_TYPE (@0)); }))))))))
+
 /* Simplify:
 
      a = a1 op a2

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr95527.c b/gcc/testsuite/gcc.dg/tree-ssa/pr95527.c
new file mode 100644 (file)
index 0000000..afd763c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr95527.c
@@ -0,0 +1,172 @@
+/* PR tree-optimization/95527 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "return 0;" 4 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "return 18;" 4 "optimized" } } */
+
+/* { dg-final { scan-tree-dump-times "a_\[0-9]*\\\(D\\\) == 0" 1 "optimized" } } */
+
+int
+f1 (int a)
+{
+  return __builtin_ffs (a) == 0;
+}
+
+/* { dg-final { scan-tree-dump-times "b_\[0-9]*\\\(D\\\) != 0" 1 "optimized" } } */
+
+int
+f2 (int b)
+{
+  return __builtin_ffs (b) != 0;
+}
+
+int
+f3 (int x)
+{
+  return __builtin_ffs (x) == -1;
+}
+
+int
+f4 (int x)
+{
+  return 17 + (__builtin_ffs (x) != -1);
+}
+
+int
+f5 (int x)
+{
+  return __builtin_ffs (x) == __SIZEOF_INT__ * __CHAR_BIT__ + 1;
+}
+
+int
+f6 (int x)
+{
+  return 17 + (__builtin_ffs (x) != __SIZEOF_INT__ * __CHAR_BIT__ + 1);
+}
+
+/* { dg-final { scan-tree-dump-times "c_\[0-9]*\\\(D\\\) & 63" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "== 32" 1 "optimized" } } */
+
+int
+f7 (int c)
+{
+  return __builtin_ffs (c) == 6;
+}
+
+/* { dg-final { scan-tree-dump-times "d_\[0-9]*\\\(D\\\) & 16383" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "!= 8192" 1 "optimized" } } */
+
+int
+f8 (int d)
+{
+  return __builtin_ffs (d) != 14;
+}
+
+/* { dg-final { scan-tree-dump-times "e_\[0-9]*\\\(D\\\) == -9223372036854775808" 1 "optimized" { target lp64 } } } */
+/* { dg-final { scan-tree-dump-times "e_\[0-9]*\\\(D\\\) == -2147483648" 1 "optimized" { target ilp32 } } } */
+
+int
+f9 (long int e)
+{
+  return __builtin_ffsl (e) == __SIZEOF_LONG__ * __CHAR_BIT__;
+}
+
+/* { dg-final { scan-tree-dump-times "f_\[0-9]*\\\(D\\\) != -9223372036854775808" 1 "optimized" } } */
+
+int
+f10 (long long int f)
+{
+  return __builtin_ffsll (f) != __SIZEOF_LONG_LONG__ * __CHAR_BIT__;
+}
+
+/* { dg-final { scan-tree-dump-times "g_\[0-9]*\\\(D\\\) != 0" 1 "optimized" } } */
+
+int
+f11 (long long int g)
+{
+  return __builtin_ffsll (g) > 0;
+}
+
+/* { dg-final { scan-tree-dump-times "h_\[0-9]*\\\(D\\\) == 0" 1 "optimized" } } */
+
+int
+f12 (int h)
+{
+  return __builtin_ffs (h) <= 0;
+}
+
+int
+f13 (int x)
+{
+  return 17 + (__builtin_ffs (x) > -1);
+}
+
+int
+f14 (int x)
+{
+  return __builtin_ffs (x) <= -1;
+}
+
+int
+f15 (int x)
+{
+  return __builtin_ffs (x) > __SIZEOF_INT__ * __CHAR_BIT__;
+}
+
+int
+f16 (int x)
+{
+  return 17 + (__builtin_ffs (x) <= __SIZEOF_INT__ * __CHAR_BIT__);
+}
+
+/* { dg-final { scan-tree-dump-times "i_\[0-9]*\\\(D\\\) & 63" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "i_\[0-9]*\\\(D\\\) != 0" 1 "optimized" } } */
+
+int
+f17 (int i)
+{
+  return __builtin_ffs (i) > 6;
+}
+
+/* { dg-final { scan-tree-dump-times "j_\[0-9]*\\\(D\\\) & 4095" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "j_\[0-9]*\\\(D\\\) == 0" 1 "optimized" } } */
+
+int
+f18 (int j)
+{
+  return __builtin_ffs (j) <= 12;
+}
+
+/* { dg-final { scan-tree-dump-times "k_\[0-9]*\\\(D\\\) == -2147483648" 1 "optimized" { target int32 } } } */
+
+int
+f19 (int k)
+{
+  return __builtin_ffs (k) > __SIZEOF_INT__ * __CHAR_BIT__ - 1;
+}
+
+/* { dg-final { scan-tree-dump-times "l_\[0-9]*\\\(D\\\) != -2147483648" 1 "optimized" { target int32 } } } */
+
+int
+f20 (int l)
+{
+  return __builtin_ffs (l) <= __SIZEOF_INT__ * __CHAR_BIT__ - 1;
+}
+
+/* { dg-final { scan-tree-dump-times "m_\[0-9]*\\\(D\\\) & 1073741823" 1 "optimized" { target int32 } } } */
+/* { dg-final { scan-tree-dump-times "m_\[0-9]*\\\(D\\\) != 0" 1 "optimized" } } */
+
+int
+f21 (int m)
+{
+  return __builtin_ffs (m) > __SIZEOF_INT__ * __CHAR_BIT__ - 2;
+}
+
+/* { dg-final { scan-tree-dump-times "n_\[0-9]*\\\(D\\\) & 1073741823" 1 "optimized" { target int32 } } } */
+/* { dg-final { scan-tree-dump-times "n_\[0-9]*\\\(D\\\) == 0" 1 "optimized" } } */
+
+int
+f22 (int n)
+{
+  return __builtin_ffs (n) <= __SIZEOF_INT__ * __CHAR_BIT__ - 2;
+}