From d6e86a67bbf791d19d7637cdcca69de3904470af Mon Sep 17 00:00:00 2001
From: zhouji <956133287@qq.com>
Date: Mon, 24 May 2021 17:09:29 +0800
Subject: [PATCH] =?UTF-8?q?[add]=20=E5=9C=A8cortex-a=E4=B8=AD=E5=A2=9E?=
 =?UTF-8?q?=E5=8A=A0=EF=BC=8C=E6=89=93=E5=BC=80RT=5FUSING=5FCPU=5FFFS?=
 =?UTF-8?q?=E5=AE=8F=E5=AE=9A=E4=B9=89=E6=97=B6=E7=9A=84=5Frt=5Fffs?=
 =?UTF-8?q?=E5=AE=9E=E7=8E=B0=E3=80=82?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 libcpu/arm/cortex-a/cpu.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/libcpu/arm/cortex-a/cpu.c b/libcpu/arm/cortex-a/cpu.c
index 7367bddd9f..c95c58a13c 100644
--- a/libcpu/arm/cortex-a/cpu.c
+++ b/libcpu/arm/cortex-a/cpu.c
@@ -75,4 +75,21 @@ RT_WEAK void rt_hw_cpu_shutdown()
     }
 }
 
+#ifdef RT_USING_CPU_FFS
+/**
+ * This function finds the first bit set (beginning with the least significant bit)
+ * in value and return the index of that bit.
+ *
+ * Bits are numbered starting at 1 (the least significant bit).  A return value of
+ * zero from any of these functions means that the argument was zero.
+ *
+ * @return return the index of the first bit set. If value is 0, then this function
+ * shall return 0.
+ */
+int __rt_ffs(int value)
+{
+    return __builtin_ffs(value);
+}
+#endif
+
 /*@}*/