lkml.org 
[lkml]   [2023]   [Nov]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] riscv: Optimize hweight API with Zbb extension
Date
The Hamming Weight of a number is the total number of bits set in it, so
the cpop/cpopw instruction from Zbb extension can be used to accelerate
hweight() API.

Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
---
arch/riscv/include/asm/arch_hweight.h | 78 +++++++++++++++++++++++++++
arch/riscv/include/asm/bitops.h | 4 +-
2 files changed, 81 insertions(+), 1 deletion(-)
create mode 100644 arch/riscv/include/asm/arch_hweight.h

diff --git a/arch/riscv/include/asm/arch_hweight.h b/arch/riscv/include/asm/arch_hweight.h
new file mode 100644
index 000000000000..c20236a0725b
--- /dev/null
+++ b/arch/riscv/include/asm/arch_hweight.h
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Based on arch/x86/include/asm/arch_hweight.h
+ */
+
+#ifndef _ASM_RISCV_HWEIGHT_H
+#define _ASM_RISCV_HWEIGHT_H
+
+#include <asm/alternative-macros.h>
+#include <asm/hwcap.h>
+
+#if (BITS_PER_LONG == 64)
+#define CPOPW "cpopw "
+#elif (BITS_PER_LONG == 32)
+#define CPOPW "cpop "
+#else
+#error "Unexpected BITS_PER_LONG"
+#endif
+
+static __always_inline unsigned int __arch_hweight32(unsigned int w)
+{
+#ifdef CONFIG_RISCV_ISA_ZBB
+ asm_volatile_goto(ALTERNATIVE("j %l[legacy]", "nop", 0,
+ RISCV_ISA_EXT_ZBB, 1)
+ : : : : legacy);
+
+ asm (".option push\n"
+ ".option arch,+zbb\n"
+ CPOPW "%0, %0\n"
+ ".option pop\n"
+ : "+r" (w) : :);
+
+ return w;
+
+legacy:
+#endif
+ return __sw_hweight32(w);
+}
+
+static inline unsigned int __arch_hweight16(unsigned int w)
+{
+ return __arch_hweight32(w & 0xffff);
+}
+
+static inline unsigned int __arch_hweight8(unsigned int w)
+{
+ return __arch_hweight32(w & 0xff);
+}
+
+#if BITS_PER_LONG == 64
+static __always_inline unsigned long __arch_hweight64(__u64 w)
+{
+# ifdef CONFIG_RISCV_ISA_ZBB
+ asm_volatile_goto(ALTERNATIVE("j %l[legacy]", "nop", 0,
+ RISCV_ISA_EXT_ZBB, 1)
+ : : : : legacy);
+
+ asm (".option push\n"
+ ".option arch,+zbb\n"
+ "cpop %0, %0\n"
+ ".option pop\n"
+ : "+r" (w) : :);
+
+ return w;
+
+legacy:
+# endif
+ return __sw_hweight64(w);
+}
+#else /* BITS_PER_LONG == 64 */
+static inline unsigned long __arch_hweight64(__u64 w)
+{
+ return __arch_hweight32((u32)w) +
+ __arch_hweight32((u32)(w >> 32));
+}
+#endif /* !(BITS_PER_LONG == 64) */
+
+#endif /* _ASM_RISCV_HWEIGHT_H */
diff --git a/arch/riscv/include/asm/bitops.h b/arch/riscv/include/asm/bitops.h
index b212c2708cda..f7c167646460 100644
--- a/arch/riscv/include/asm/bitops.h
+++ b/arch/riscv/include/asm/bitops.h
@@ -271,7 +271,9 @@ static __always_inline int variable_fls(unsigned int x)
#include <asm-generic/bitops/fls64.h>
#include <asm-generic/bitops/sched.h>

-#include <asm-generic/bitops/hweight.h>
+#include <asm/arch_hweight.h>
+
+#include <asm-generic/bitops/const_hweight.h>

#if (BITS_PER_LONG == 64)
#define __AMO(op) "amo" #op ".d"
--
2.25.1
\
 
 \ /
  Last update: 2023-11-20 13:57    [W:0.057 / U:0.932 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site