[Buildroot] Analysis of build results

[Peter Seiderer <ps.report@gmx.net>]

Hello Romain,

On Fri, 28 Feb 2020 08:32:18 +0100, Romain Naour <romain.naour@gmail.com> wrote:

> >
> > >     arm      |         mesa3d-19.3.4          | NOK |
> > http://autobuild.buildroot.net/results/6387b0a99e1a0922811919623d9a10b0943988df
> > |
> >
> > {standard input}: Assembler messages:
> > {standard input}:334: Error: selected processor does not support `vldm
> > r4,{q0,q1,q2,q3}' in ARM mode
> > {standard input}:335: Error: selected processor does not support `vst1.8
> > d0,[r3],r2' in ARM mode
> > {standard input}:336: Error: selected processor does not support `vst1.8
> > d1,[r3],r2' in ARM mode
> > {standard input}:337: Error: selected processor does not support `vst1.8
> > d2,[r3],r2' in ARM mode
> >
> > Bad stuff happens when building the vc4 driver. It probably needs some
> > minimal ARM architecture variant.
> >
>
> I believe we should re-add the dependency on neon for vc4 driver. There is
> -mfpu=neon added by the build system.

The BR2_ARM_CPU_HAS_NEON dependency was dropped with commit [1] because mesa3d
commit [2] added a compile time detected neon support, in the meantime this
was changed to a runtime detection [3] and finally enabled for the meson
cross compile build with commit [4] (assuming toolchain support for the
neon assembler instructions)...

Maybe the compile error could be fixed by re-adding partly the compile time
check for the neon support (tested):

--- mesa3d-19.3.4/src/broadcom/common/v3d_cpu_tiling.h_orig	2020-02-28 14:47:44.232634657 +0100
+++ mesa3d-19.3.4/src/broadcom/common/v3d_cpu_tiling.h	2020-02-28 14:49:21.518425222 +0100
@@ -31,7 +31,7 @@
 v3d_load_utile(void *cpu, uint32_t cpu_stride,
                void *gpu, uint32_t gpu_stride)
 {
-#if defined(V3D_BUILD_NEON) && defined(PIPE_ARCH_ARM)
+#if defined(V3D_BUILD_NEON) && defined(__ARM_ARCH) && __ARM_ARCH >= 7
         if (gpu_stride == 8) {
                 __asm__ volatile (
                         /* Load from the GPU in one shot, no interleave, to
@@ -141,7 +141,7 @@
 v3d_store_utile(void *gpu, uint32_t gpu_stride,
                 void *cpu, uint32_t cpu_stride)
 {
-#if defined(V3D_BUILD_NEON) && defined(PIPE_ARCH_ARM)
+#if defined(V3D_BUILD_NEON) && defined(__ARM_ARCH) && __ARM_ARCH >= 7
         if (gpu_stride == 8) {
                 __asm__ volatile (
                         /* Load each 8-byte line from cpu-side source,

Regards,
Peter

[1] https://git.buildroot.net/buildroot/commit/package/mesa3d?id=350cb0d32ece533b9723a5f3ca6fbf7e6f071c90
[2] https://cgit.freedesktop.org/mesa/mesa/commit/?h=17.1&id=4d30024238efa829cabc72c1601beeee18c3dbf2
[3] https://cgit.freedesktop.org/mesa/mesa/commit/?h=staging/19.3&id=ece06defe77a77d2db40abeddee5a2e0e45654ce
[4] https://cgit.freedesktop.org/mesa/mesa/commit/?id=932ed9c00b99e6ec92146ec9e820f546cf3e6551

>
> Romain