linux-kernel - [PATCH 4.14 077/105] raid6/ppc: Fix build for clang

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Message-Id: <20190111131109.430939390@linuxfoundation.org>
Date:   Fri, 11 Jan 2019 15:14:48 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Joel Stanley <joel@....id.au>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH 4.14 077/105] raid6/ppc: Fix build for clang

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joel Stanley <joel@....id.au>

commit e213574a449f7a57d4202c1869bbc7680b6b5521 upstream.

We cannot build these files with clang as it does not allow altivec
instructions in assembly when -msoft-float is passed.

Jinsong Ji <jji@...ibm.com> wrote:
> We currently disable Altivec/VSX support when enabling soft-float.  So
> any usage of vector builtins will break.
>
> Enable Altivec/VSX with soft-float may need quite some clean up work, so
> I guess this is currently a limitation.
>
> Removing -msoft-float will make it work (and we are lucky that no
> floating point instructions will be generated as well).

This is a workaround until the issue is resolved in clang.

Link: https://bugs.llvm.org/show_bug.cgi?id=31177
Link: https://github.com/ClangBuiltLinux/linux/issues/239
Signed-off-by: Joel Stanley <joel@....id.au>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
[nc: Use 'ifeq ($(cc-name),clang)' instead of 'ifdef CONFIG_CC_IS_CLANG'
     because that config does not exist in 4.14; the Kconfig rewrite
     that added that config happened in 4.18]
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 lib/raid6/Makefile |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

--- a/lib/raid6/Makefile
+++ b/lib/raid6/Makefile
@@ -18,6 +18,21 @@ quiet_cmd_unroll = UNROLL  $@
 
 ifeq ($(CONFIG_ALTIVEC),y)
 altivec_flags := -maltivec $(call cc-option,-mabi=altivec)
+
+ifeq ($(cc-name),clang)
+# clang ppc port does not yet support -maltivec when -msoft-float is
+# enabled. A future release of clang will resolve this
+# https://bugs.llvm.org/show_bug.cgi?id=31177
+CFLAGS_REMOVE_altivec1.o  += -msoft-float
+CFLAGS_REMOVE_altivec2.o  += -msoft-float
+CFLAGS_REMOVE_altivec4.o  += -msoft-float
+CFLAGS_REMOVE_altivec8.o  += -msoft-float
+CFLAGS_REMOVE_altivec8.o  += -msoft-float
+CFLAGS_REMOVE_vpermxor1.o += -msoft-float
+CFLAGS_REMOVE_vpermxor2.o += -msoft-float
+CFLAGS_REMOVE_vpermxor4.o += -msoft-float
+CFLAGS_REMOVE_vpermxor8.o += -msoft-float
+endif
 endif
 
 # The GCC option -ffreestanding is required in order to compile code containing