On December 31, 2020 10:37:46 AM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>The following patch adds some clz simplifications. If
>clz is 0, then the MSB of the argument is set, and if clz is prec-1,
>then
>the argument is 1.
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok.
Richard.
>2020-12-31 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/94802
> * match.pd (clz(X) == 0 -> (int)X < 0): New simplification.
> (clz(X) == (prec-1) -> X == 1): Likewise.
>
> * gcc.dg/tree-ssa/pr94802-1.c: New test.
>
>--- gcc/match.pd.jj 2020-12-30 12:00:00.924301784 +0100
>+++ gcc/match.pd 2020-12-30 17:04:27.340815135 +0100
>@@ -6226,6 +6226,39 @@ (define_operator_list COND_TERNARY
> (if (single_use (@3))
> (IFN_FMA @0 @1 @2))))
>
>+/* CLZ simplifications. */
>+(for clz (CLZ)
>+ (for op (eq ne)
>+ cmp (lt ge)
>+ (simplify
>+ (op (clz:s @0) INTEGER_CST@1)
>+ (if (integer_zerop (@1))
>+ /* clz(X) == 0 is (int)X < 0 and clz(X) != 0 is (int)X >= 0. */
>+ (with { tree stype = signed_type_for (TREE_TYPE (@0));
>+ HOST_WIDE_INT val = 0;
>+#ifdef CLZ_DEFINED_VALUE_AT_ZERO
>+ /* Punt on hypothetical weird targets. */
>+ if (CLZ_DEFINED_VALUE_AT_ZERO (TYPE_MODE (TREE_TYPE (@0)),
>+ val) == 2
>+ && val == 0)
>+ stype = NULL_TREE;
>+#endif
>+ }
>+ (if (stype)
>+ (cmp (convert:stype @0) { build_zero_cst (stype); })))
>+ /* clz(X) == (prec-1) is X == 1 and clz(X) != (prec-1) is X != 1.
>*/
>+ (with { bool ok = true;
>+#ifdef CLZ_DEFINED_VALUE_AT_ZERO
>+ /* Punt on hypothetical weird targets. */
>+ if (CLZ_DEFINED_VALUE_AT_ZERO (TYPE_MODE (TREE_TYPE (@0)),
>+ val) == 2
>+ && val == TYPE_PRECISION (TREE_TYPE (@0)) - 1)
>+ ok = false;
>+#endif
>+ }
>+ (if (ok && wi::to_wide (@1) == (TYPE_PRECISION (TREE_TYPE (@0)) -
>1))
>+ (op @0 { build_one_cst (TREE_TYPE (@0)); })))))))
>+
> /* POPCOUNT simplifications. */
>/* popcount(X) + popcount(Y) is popcount(X|Y) when X&Y must be zero.
>*/
> (simplify
>--- gcc/testsuite/gcc.dg/tree-ssa/pr94802-1.c.jj 2020-12-30
>17:25:40.173364488 +0100
>+++ gcc/testsuite/gcc.dg/tree-ssa/pr94802-1.c 2020-12-30
>17:26:06.687063794 +0100
>@@ -0,0 +1,68 @@
>+/* PR tree-optimization/94802 */
>+/* { dg-do run } */
>+/* { dg-options "-O2 -fdump-tree-optimized" } */
>+/* { dg-final { scan-tree-dump-not " = __builtin_clz " "optimized" } }
>*/
>+
>+__attribute__((noipa)) int
>+f1 (int a, int b)
>+{
>+ return __builtin_clz (a - b) != 0;
>+}
>+
>+__attribute__((noipa)) int
>+f2 (int x)
>+{
>+ return __builtin_clz (x) == 0;
>+}
>+
>+__attribute__((noipa)) int
>+f3 (int x)
>+{
>+ return __builtin_clz (x) != 0;
>+}
>+
>+__attribute__((noipa)) int
>+f4 (int a, int b)
>+{
>+ return __builtin_clz (a - b) == sizeof (int) * __CHAR_BIT__ - 1;
>+}
>+
>+__attribute__((noipa)) int
>+f5 (int x)
>+{
>+ return __builtin_clz (x) == sizeof (int) * __CHAR_BIT__ - 1;
>+}
>+
>+__attribute__((noipa)) int
>+f6 (int x)
>+{
>+ return __builtin_clz (x) != sizeof (int) * __CHAR_BIT__ - 1;
>+}
>+
>+int
>+main ()
>+{
>+ if (f1 (5, 7) != 0
>+ || f1 (7, 5) != 1
>+ || f2 (1) != 0
>+ || f2 (137) != 0
>+ || f2 (-1) != 1
>+ || f2 (-137) != 1
>+ || f3 (1) != 1
>+ || f3 (137) != 1
>+ || f3 (-1) != 0
>+ || f3 (-137) != 0
>+ || f4 (5, 4) != 1
>+ || f4 (6, 4) != 0
>+ || f4 (4, 5) != 0
>+ || f5 (1) != 1
>+ || f5 (17) != 0
>+ || f5 (-1) != 0
>+ || f5 (-17) != 0
>+ || f6 (1) != 0
>+ || f6 (17) != 1
>+ || f6 (-1) != 1
>+ || f6 (-17) != 1)
>+ __builtin_abort ();
>+ return 0;
>+}
>
> Jakub
