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From: Adrian Ratiu <adrian.ratiu@collabora.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Nathan Chancellor <natechancellor@gmail.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Russell King <linux@armlinux.org.uk>,
	Ard Biesheuvel <ardb@kernel.org>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	kernel@collabora.com,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [PATCH v4 2/2] arm: lib: xor-neon: move pragma options to makefile
Date: Tue, 19 Jan 2021 15:17:24 +0200	[thread overview]
Message-ID: <20210119131724.308884-3-adrian.ratiu@collabora.com> (raw)
In-Reply-To: <20210119131724.308884-1-adrian.ratiu@collabora.com>

Using a pragma like GCC optimize is a bad idea because it tags
all functions with an __attribute__((optimize)) which replaces
optimization options rather than appending so could result in
dropping important flags. Not recommended for production use.

Because these options should always be enabled for this file,
it's better to set them via command line. tree-vectorize is on
by default in Clang, but it doesn't hurt to make it explicit.

Suggested-by: Arvind Sankar <nivedita@alum.mit.edu>
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
---
 arch/arm/lib/Makefile   |  2 +-
 arch/arm/lib/xor-neon.c | 10 ----------
 2 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 6d2ba454f25b..12d31d1a7630 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -45,6 +45,6 @@ $(obj)/csumpartialcopyuser.o:	$(obj)/csumpartialcopygeneric.S
 
 ifeq ($(CONFIG_KERNEL_MODE_NEON),y)
   NEON_FLAGS			:= -march=armv7-a -mfloat-abi=softfp -mfpu=neon
-  CFLAGS_xor-neon.o		+= $(NEON_FLAGS)
+  CFLAGS_xor-neon.o		+= $(NEON_FLAGS) -ftree-vectorize -Wno-unused-variable
   obj-$(CONFIG_XOR_BLOCKS)	+= xor-neon.o
 endif
diff --git a/arch/arm/lib/xor-neon.c b/arch/arm/lib/xor-neon.c
index f9f3601cc2d1..65125ce69044 100644
--- a/arch/arm/lib/xor-neon.c
+++ b/arch/arm/lib/xor-neon.c
@@ -23,16 +23,6 @@ MODULE_LICENSE("GPL");
 #warning Clang does not vectorize code in this file.
 #endif
 
-/*
- * Pull in the reference implementations while instructing GCC (through
- * -ftree-vectorize) to attempt to exploit implicit parallelism and emit
- * NEON instructions.
- */
-#ifdef CONFIG_CC_IS_GCC
-#pragma GCC optimize "tree-vectorize"
-#endif
-
-#pragma GCC diagnostic ignored "-Wunused-variable"
 #include <asm-generic/xor.h>
 
 struct xor_block_template const xor_block_neon_inner = {
-- 
2.30.0


WARNING: multiple messages have this Message-ID (diff)
From: Adrian Ratiu <adrian.ratiu@collabora.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Arnd Bergmann <arnd@arndb.de>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Russell King <linux@armlinux.org.uk>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	Nathan Chancellor <natechancellor@gmail.com>,
	kernel@collabora.com, Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH v4 2/2] arm: lib: xor-neon: move pragma options to makefile
Date: Tue, 19 Jan 2021 15:17:24 +0200	[thread overview]
Message-ID: <20210119131724.308884-3-adrian.ratiu@collabora.com> (raw)
In-Reply-To: <20210119131724.308884-1-adrian.ratiu@collabora.com>

Using a pragma like GCC optimize is a bad idea because it tags
all functions with an __attribute__((optimize)) which replaces
optimization options rather than appending so could result in
dropping important flags. Not recommended for production use.

Because these options should always be enabled for this file,
it's better to set them via command line. tree-vectorize is on
by default in Clang, but it doesn't hurt to make it explicit.

Suggested-by: Arvind Sankar <nivedita@alum.mit.edu>
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
---
 arch/arm/lib/Makefile   |  2 +-
 arch/arm/lib/xor-neon.c | 10 ----------
 2 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 6d2ba454f25b..12d31d1a7630 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -45,6 +45,6 @@ $(obj)/csumpartialcopyuser.o:	$(obj)/csumpartialcopygeneric.S
 
 ifeq ($(CONFIG_KERNEL_MODE_NEON),y)
   NEON_FLAGS			:= -march=armv7-a -mfloat-abi=softfp -mfpu=neon
-  CFLAGS_xor-neon.o		+= $(NEON_FLAGS)
+  CFLAGS_xor-neon.o		+= $(NEON_FLAGS) -ftree-vectorize -Wno-unused-variable
   obj-$(CONFIG_XOR_BLOCKS)	+= xor-neon.o
 endif
diff --git a/arch/arm/lib/xor-neon.c b/arch/arm/lib/xor-neon.c
index f9f3601cc2d1..65125ce69044 100644
--- a/arch/arm/lib/xor-neon.c
+++ b/arch/arm/lib/xor-neon.c
@@ -23,16 +23,6 @@ MODULE_LICENSE("GPL");
 #warning Clang does not vectorize code in this file.
 #endif
 
-/*
- * Pull in the reference implementations while instructing GCC (through
- * -ftree-vectorize) to attempt to exploit implicit parallelism and emit
- * NEON instructions.
- */
-#ifdef CONFIG_CC_IS_GCC
-#pragma GCC optimize "tree-vectorize"
-#endif
-
-#pragma GCC diagnostic ignored "-Wunused-variable"
 #include <asm-generic/xor.h>
 
 struct xor_block_template const xor_block_neon_inner = {
-- 
2.30.0


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  parent reply	other threads:[~2021-01-19 13:27 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-19 13:17 [PATCH v4 0/2] xor-neon: Remove GCC warn & pragmas Adrian Ratiu
2021-01-19 13:17 ` Adrian Ratiu
2021-01-19 13:17 ` [PATCH v4 1/2] arm: lib: xor-neon: remove unnecessary GCC < 4.6 warning Adrian Ratiu
2021-01-19 13:17   ` Adrian Ratiu
2021-01-19 21:18   ` Nick Desaulniers
2021-01-19 21:18     ` Nick Desaulniers
2021-01-19 21:34     ` Arnd Bergmann
2021-01-19 21:34       ` Arnd Bergmann
2021-01-19 22:04       ` Nick Desaulniers
2021-01-19 22:04         ` Nick Desaulniers
2021-01-19 23:10         ` Nick Desaulniers
2021-01-19 23:10           ` Nick Desaulniers
2021-01-20 23:09       ` Nick Desaulniers
2021-01-20 23:09         ` Nick Desaulniers
2021-01-20 23:15         ` Nick Desaulniers
2021-01-20 23:15           ` Nick Desaulniers
2021-01-21  4:13         ` Arvind Sankar
2021-01-21  4:13           ` Arvind Sankar
2021-01-21  4:24           ` Nick Desaulniers
2021-01-21  4:24             ` Nick Desaulniers
2021-01-21  8:46           ` Ard Biesheuvel
2021-01-21  8:46             ` Ard Biesheuvel
2021-01-20 13:11     ` Adrian Ratiu
2021-01-20 13:11       ` Adrian Ratiu
2021-01-19 21:54   ` Nathan Chancellor
2021-01-19 21:54     ` Nathan Chancellor
2021-01-20 13:18     ` Adrian Ratiu
2021-01-20 13:18       ` Adrian Ratiu
2021-01-19 22:04   ` David Laight
2021-01-19 22:04     ` David Laight
2021-01-19 22:05     ` Nick Desaulniers
2021-01-19 22:05       ` Nick Desaulniers
2021-01-19 13:17 ` Adrian Ratiu [this message]
2021-01-19 13:17   ` [PATCH v4 2/2] arm: lib: xor-neon: move pragma options to makefile Adrian Ratiu

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