From d6c4badffafa295f6082b7d74de314e131f30a96 Mon Sep 17 00:00:00 2001
From: Richard Sandiford <richard.sandiford@arm.com>
Date: Thu, 24 Oct 2024 14:22:33 +0100
Subject: [PATCH] Handle POLY_INT_CSTs in get_nonzero_bits
This patch extends get_nonzero_bits to handle POLY_INT_CSTs,
The easiest (but also most useful) case is that the number
of trailing zeros in the runtime value is at least the number
of trailing zeros in each individual component.
In principle, we could do this for coeffs 1 and above only,
and then OR in ceoff 0. This would give ~0x11 for [14, 32], say.
But that's future work.
gcc/
* tree-ssanames.cc (get_nonzero_bits): Handle POLY_INT_CSTs.
* match.pd (with_possible_nonzero_bits): Likewise.
gcc/testsuite/
* gcc.target/aarch64/sve/cnt_fold_4.c: New test.
---
gcc/match.pd | 2 +
.../gcc.target/aarch64/sve/cnt_fold_4.c | 61 +++++++++++++++++++
gcc/tree-ssanames.cc | 3 +
3 files changed, 66 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/cnt_fold_4.c
diff --git a/gcc/match.pd b/gcc/match.pd
index 17613ec8ade4..391c60bdfb32 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2872,6 +2872,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
possibly set. */
(match with_possible_nonzero_bits
INTEGER_CST@0)
+(match with_possible_nonzero_bits
+ POLY_INT_CST@0)
(match with_possible_nonzero_bits
SSA_NAME@0
(if (INTEGRAL_TYPE_P (TREE_TYPE (@0)) || POINTER_TYPE_P (TREE_TYPE (@0)))))
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/cnt_fold_4.c b/gcc/testsuite/gcc.target/aarch64/sve/cnt_fold_4.c
new file mode 100644
index 000000000000..b7a53701993c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/cnt_fold_4.c
@@ -0,0 +1,61 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-final { check-function-bodies "**" "" } } */
+
+#include <arm_sve.h>
+
+/*
+** f1:
+** cnth x0
+** ret
+*/
+uint64_t
+f1 ()
+{
+ uint64_t x = svcntw ();
+ x >>= 2;
+ return x << 3;
+}
+
+/*
+** f2:
+** [^\n]+
+** [^\n]+
+** ...
+** ret
+*/
+uint64_t
+f2 ()
+{
+ uint64_t x = svcntd ();
+ x >>= 2;
+ return x << 3;
+}
+
+/*
+** f3:
+** cntb x0, all, mul #4
+** ret
+*/
+uint64_t
+f3 ()
+{
+ uint64_t x = svcntd ();
+ x >>= 1;
+ return x << 6;
+}
+
+/*
+** f4:
+** [^\n]+
+** [^\n]+
+** ...
+** ret
+*/
+uint64_t
+f4 ()
+{
+ uint64_t x = svcntd ();
+ x >>= 2;
+ return x << 2;
+}
diff --git a/gcc/tree-ssanames.cc b/gcc/tree-ssanames.cc
index 4f83fcbb5171..ae6a0cd48fe6 100644
--- a/gcc/tree-ssanames.cc
+++ b/gcc/tree-ssanames.cc
@@ -502,6 +502,9 @@ get_nonzero_bits (const_tree name)
if (TREE_CODE (name) == INTEGER_CST)
return wi::to_wide (name);
+ if (POLY_INT_CST_P (name))
+ return -known_alignment (wi::to_poly_wide (name));
+
/* Use element_precision instead of TYPE_PRECISION so complex and
vector types get a non-zero precision. */
unsigned int precision = element_precision (TREE_TYPE (name));
--
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