diff options
author | Vincent Palatin <vpalatin@chromium.org> | 2014-03-03 11:51:37 -0800 |
---|---|---|
committer | chrome-internal-fetch <chrome-internal-fetch@google.com> | 2014-03-06 21:32:57 +0000 |
commit | 6ab4ad5f95ea86156d0e47b806c7a6bcfbae67d8 (patch) | |
tree | ecc0aa5da00777b478ce3ebdc53ed07eac4ec25c /common/clz.c | |
parent | 75f59a47ec90bfd4f21bfbab7536c4ad13847595 (diff) | |
download | chrome-ec-6ab4ad5f95ea86156d0e47b806c7a6bcfbae67d8.tar.gz |
Move CLZ emulation to common code
Move the CLZ instruction emulation C code to the common directory, so it
can be reused for all CPU cores missing a CLZ instruction (e.g. CortexM0).
Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
BRANCH=none
BUG=none
TEST=run EC console on STM32F072B Discovery board with Cortex-M0 core,
and pass all available unit-tests on target.
Change-Id: Ief56cac7430fcb0fbced8a8925250c89cbd0bcfc
Reviewed-on: https://chromium-review.googlesource.com/188981
Reviewed-by: Alec Berg <alecaberg@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Queue: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>
Diffstat (limited to 'common/clz.c')
-rw-r--r-- | common/clz.c | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/common/clz.c b/common/clz.c new file mode 100644 index 0000000000..30c987e367 --- /dev/null +++ b/common/clz.c @@ -0,0 +1,42 @@ +/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved. + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + * + * Software emulation for CLZ instruction + */ + +/** + * Count leading zeros + * + * @param x non null integer. + * @return the number of leading 0-bits in x, + * starting at the most significant bit position. + */ +int __clzsi2(int x) +{ + int r = 0; + + if (!x) + return 32; + if (!(x & 0xffff0000u)) { + x <<= 16; + r += 16; + } + if (!(x & 0xff000000u)) { + x <<= 8; + r += 8; + } + if (!(x & 0xf0000000u)) { + x <<= 4; + r += 4; + } + if (!(x & 0xc0000000u)) { + x <<= 2; + r += 2; + } + if (!(x & 0x80000000u)) { + x <<= 1; + r += 1; + } + return r; +} |