From a26276b9498843218ee78c956c478ceebb819ad8 Mon Sep 17 00:00:00 2001
From: Haibo Xu <haibo.xu@arm.com>
Date: Tue, 20 Aug 2019 09:44:05 +0000
Subject: [PATCH] Enable pkg/bits support on arm64.

Signed-off-by: Haibo Xu <haibo.xu@arm.com>
Change-Id: I490716f0e6204f0b3a43f71931b10d1ca541e128
---
 pkg/bits/BUILD                                |  3 +-
 .../{uint64_arch_amd64.go => uint64_arch.go}  |  2 +-
 pkg/bits/uint64_arch_arm64_asm.s              | 33 +++++++++++++++++++
 pkg/bits/uint64_arch_generic.go               |  2 +-
 4 files changed, 37 insertions(+), 3 deletions(-)
 rename pkg/bits/{uint64_arch_amd64.go => uint64_arch.go} (98%)
 create mode 100644 pkg/bits/uint64_arch_arm64_asm.s

diff --git a/pkg/bits/BUILD b/pkg/bits/BUILD
index 51967b811..1b5dac99a 100644
--- a/pkg/bits/BUILD
+++ b/pkg/bits/BUILD
@@ -11,8 +11,9 @@ go_library(
         "bits.go",
         "bits32.go",
         "bits64.go",
-        "uint64_arch_amd64.go",
+        "uint64_arch.go",
         "uint64_arch_amd64_asm.s",
+        "uint64_arch_arm64_asm.s",
         "uint64_arch_generic.go",
     ],
     importpath = "gvisor.dev/gvisor/pkg/bits",
diff --git a/pkg/bits/uint64_arch_amd64.go b/pkg/bits/uint64_arch.go
similarity index 98%
rename from pkg/bits/uint64_arch_amd64.go
rename to pkg/bits/uint64_arch.go
index faccaa61a..9f23eff77 100644
--- a/pkg/bits/uint64_arch_amd64.go
+++ b/pkg/bits/uint64_arch.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// +build amd64
+// +build amd64 arm64
 
 package bits
 
diff --git a/pkg/bits/uint64_arch_arm64_asm.s b/pkg/bits/uint64_arch_arm64_asm.s
new file mode 100644
index 000000000..814ba562d
--- /dev/null
+++ b/pkg/bits/uint64_arch_arm64_asm.s
@@ -0,0 +1,33 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build arm64
+
+TEXT ·TrailingZeros64(SB),$0-16
+  MOVD  x+0(FP), R0
+  RBIT  R0, R0
+  CLZ   R0, R0        // return 64 if x == 0
+  MOVD  R0, ret+8(FP)
+  RET
+
+TEXT ·MostSignificantOne64(SB),$0-16
+  MOVD  x+0(FP), R0
+  CLZ   R0, R0        // return 64 if x == 0
+  MOVD  $63, R1
+  SUBS  R0, R1, R0    // ret = 63 - CLZ
+  BPL   end
+  MOVD  $64, R0       // x == 0
+end:
+  MOVD  R0, ret+8(FP)
+  RET
diff --git a/pkg/bits/uint64_arch_generic.go b/pkg/bits/uint64_arch_generic.go
index 7dd2d1480..9dd2098d1 100644
--- a/pkg/bits/uint64_arch_generic.go
+++ b/pkg/bits/uint64_arch_generic.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// +build !amd64
+// +build !amd64,!arm64
 
 package bits