Dear all,
This is v3 of the patch series started at
id:[email protected]
This series does not address the Clang -ftree-vectorize not
working bug which is a known pre-existing issued documented
at [1] [2] [3]. Clang vectorization needs to be investigated
in more deepth and fixed separately. The purpouse of this is
to only fix some low-hanging-fruit GCC related isues.
Tested on next-20201112 using GCC 10.2.0 and Clang 10.0.1.
[1] https://bugs.llvm.org/show_bug.cgi?id=40976
[2] https://github.com/ClangBuiltLinux/linux/issues/503
[3] https://github.com/ClangBuiltLinux/linux/issues/496
Kind regards,
Adrian
Chnages in v3:
- Reworded first commit (Ard)
- Added tags by Nick and Nathan
Changes in v2:
- Dropped the patch which disabled Clang vectorization (Nick)
- Added new patch to move pragmas to makefile cmdline options
(Arvid and Ard)
Adrian Ratiu (1):
arm: lib: xor-neon: move pragma options to makefile
Nathan Chancellor (1):
arm: lib: xor-neon: remove unnecessary GCC < 4.6 warning
arch/arm/lib/Makefile | 2 +-
arch/arm/lib/xor-neon.c | 17 -----------------
2 files changed, 1 insertion(+), 18 deletions(-)
--
2.29.2
From: Nathan Chancellor <[email protected]>
Drop warning because kernel now requires GCC >= v4.9 after
commit 6ec4476ac825 ("Raise gcc version requirement to 4.9")
and clarify that -ftree-vectorize now always needs enabling
for GCC by directly testing the presence of CONFIG_CC_IS_GCC.
Another reason to remove the warning is that Clang exposes
itself as GCC < 4.6 so it triggers the warning about GCC
which doesn't make much sense and risks misleading users.
As a side-note remark, -fttree-vectorize is on by default in
Clang, but it currently does not work (see linked issues).
Link: https://github.com/ClangBuiltLinux/linux/issues/496
Link: https://github.com/ClangBuiltLinux/linux/issues/503
Reported-by: Nick Desaulniers <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
Signed-off-by: Adrian Ratiu <[email protected]>
---
arch/arm/lib/xor-neon.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/arch/arm/lib/xor-neon.c b/arch/arm/lib/xor-neon.c
index b99dd8e1c93f..e1e76186ec23 100644
--- a/arch/arm/lib/xor-neon.c
+++ b/arch/arm/lib/xor-neon.c
@@ -19,15 +19,8 @@ MODULE_LICENSE("GPL");
* -ftree-vectorize) to attempt to exploit implicit parallelism and emit
* NEON instructions.
*/
-#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
+#ifdef CONFIG_CC_IS_GCC
#pragma GCC optimize "tree-vectorize"
-#else
-/*
- * While older versions of GCC do not generate incorrect code, they fail to
- * recognize the parallel nature of these functions, and emit plain ARM code,
- * which is known to be slower than the optimized ARM code in asm-arm/xor.h.
- */
-#warning This code requires at least version 4.6 of GCC
#endif
#pragma GCC diagnostic ignored "-Wunused-variable"
--
2.29.2