From: remi@remlab.net
To: ffmpeg-devel@ffmpeg.org
Subject: [FFmpeg-devel] [PATCH 03/18] configure/riscv: detect fast CLZ
Date: Fri, 9 Sep 2022 18:48:44 +0300
Message-ID: <20220909154859.68954-3-remi@remlab.net> (raw)
From: Rémi Denis-Courmont <remi@remlab.net>
RISC-V defines the CLZ instruction as part of the ratified Zbb subset
of the (not yet ratified) bit mapulation extension (B). We can detect
it from the __riscv_zbb predefined constant. At least GCC 12 already
supports this correctly.
Note that the macro will be non-zero if supported, zero if enabled
in the compiler flags (e.g. -march=rv64gzbb) but not known to the
compiler, and undefined otherwise.
---
configure | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/configure b/configure
index 9e51abd0d3..b7dc1d8656 100755
--- a/configure
+++ b/configure
@@ -5334,6 +5334,12 @@ 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:[~2022-09-09 15:49 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-09 15:48 remi [this message]
[not found] <2652141.mvXUDI8C0e@basile.remlab.net>
2022-09-12 15:53 ` remi
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