raid6/ppc: Fix build for clang

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

Jinsong Ji <[email protected]> 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: ClangBuiltLinux#239
Signed-off-by: Joel Stanley <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>

lib/raid6/Makefile

@@ -18,6 +18,21 @@ quiet_cmd_unroll = UNROLL  $@
 
 ifeq ($(CONFIG_ALTIVEC),y)
 altivec_flags := -maltivec $(call cc-option,-mabi=altivec)
+
+ifdef CONFIG_CC_IS_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