Re: Problems building ppc images in v4.14.y and v4.16.y using gcc 7.3.0 / 8.1.0 from kernel.org

On Tue, Jun 5, 2018 at 3:52 PM, Guenter Roeck [off-list ref] wrote:

Hi Arnd,

when using the ppc64 compiler from kernel.org, I see the following problems
when trying to compile ppc:allnoconfig in v4.14.y or v4.16.y.

gcc 7.3.0: Compilation of kernel.cpu.o hangs

The problem goes away if I apply the following two patches (tested with
4.16.y)

17a2f1ced028 cpu/hotplug: Merge cpuhp_bp_states and cpuhp_ap_states
fcb3029a8d89 cpu/hotplug: Fix unused function warning

This is probably the same as
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84038

I thought I had included the fix in my builds.

gcc 8.1.0: Compilation of kernel/cpu.o results in the following error

powerpc64-linux-gcc: error: unrecognized command line option '-mno-spe'; did
you mean '-fno-see'?
powerpc64-linux-gcc: error: unrecognized command line option '-mspe=no'; did
you mean '-misel=no'?

This problem is also seen with mainline.

I've seen it, but couldn't figure out what the right fix is. I ended
up commenting
out those two lines in my private builds:

--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile

@@ -215,8 +215,8 @@ KBUILD_CFLAGS += $(call cc-option,-mno-vsx)

 # No SPE instruction when building kernel
 # (We use all available options to help semi-broken compilers)
-KBUILD_CFLAGS += $(call cc-option,-mno-spe)
-KBUILD_CFLAGS += $(call cc-option,-mspe=no)
+#KBUILD_CFLAGS += $(call cc-option,-mno-spe)
+#KBUILD_CFLAGS += $(call cc-option,-mspe=no)

 # Enable unit-at-a-time mode when possible. It shrinks the
 # kernel considerably.

I think there were some changes in how cc-option gets evaluated, maybe
those rely on something else to be enabled or disabled first?

        Arnd