From: remi@remlab.net
To: ffmpeg-devel@ffmpeg.org
Subject: [FFmpeg-devel] [PATCH] riscv: detect fast CLZ from Zbb extension
Date: Sat, 3 Sep 2022 15:35:59 +0300
Message-ID: <20220903123559.78526-1-remi@remlab.net> (raw)
From: Rémi Denis-Courmont <remi@remlab.net>
RISC-V defines the CLZ instruction as part of the Zbb subset of the
bit mapulation extension (B). We can detect it from the __riscv_zbb
predefined constant. It will be non-zero if supported, zero if enabled
in the compiler flags but not supported by the compiler, and undefined
otherwise.
---
configure | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/configure b/configure
index 932ea5b553..b54ff5fc44 100755
--- a/configure
+++ b/configure
@@ -5331,6 +5331,12 @@ elif enabled ppc; then
;;
esac
+elif enabled riscv; then
+
+ if test_cpp_condition stddef.h "__riscv_zbb"; then
+ enable fast_clz
+ fi
+
elif enabled sparc; then
case $cpu in
--
2.37.2
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next reply other threads:[~2022-09-03 12:36 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-03 12:35 remi [this message]
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2022-09-03 12:35 remi
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