* [FFmpeg-devel] [PATCH] riscv: detect fast CLZ from Zbb extension
@ 2022-09-03 12:35 remi
0 siblings, 0 replies; 2+ messages in thread
From: remi @ 2022-09-03 12:35 UTC (permalink / raw)
To: ffmpeg-devel
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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^ permalink raw reply [flat|nested] 2+ messages in thread* [FFmpeg-devel] [PATCH] riscv: detect fast CLZ from Zbb extension
@ 2022-09-03 12:35 remi
0 siblings, 0 replies; 2+ messages in thread
From: remi @ 2022-09-03 12:35 UTC (permalink / raw)
To: ffmpeg-devel
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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ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
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^ permalink raw reply [flat|nested] 2+ messages in thread
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2022-09-03 12:35 [FFmpeg-devel] [PATCH] riscv: detect fast CLZ from Zbb extension remi
2022-09-03 12:35 remi
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