[XEN PATCH 7/7] x86/xstate: move BUILD_BUG_ON to address MISRA C:2012 Rule 2.1

[Nicola Vetrini <nicola.vetrini@bugseng.com>]

The string literal inside the expansion of BUILD_BUG_ON is considered
unreachable code; however, such statement can be moved earlier
with no functional change.

Signed-off-by: Nicola Vetrini <nicola.vetrini@bugseng.com>
---
The motivation for this code movement is that keeping it inside the switch
statement matches MISRA's definition of unreachable code, but does not fall into
the category of declarations without initialization, which is already a deviated
aspect. An alternative approach would be to deviate BUILD_BUG_ON as well.
---
 xen/arch/x86/xstate.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
index cf94761d0542..99f0526c8988 100644
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -396,9 +396,10 @@ void xrstor(struct vcpu *v, uint64_t mask)
      */
     for ( prev_faults = faults = 0; ; prev_faults = faults )
     {
+        BUILD_BUG_ON(sizeof(faults) != 4); /* Clang doesn't support %z in asm. */
+
         switch ( __builtin_expect(ptr->fpu_sse.x[FPU_WORD_SIZE_OFFSET], 8) )
         {
-            BUILD_BUG_ON(sizeof(faults) != 4); /* Clang doesn't support %z in asm. */
 #define _xrstor(insn) \
         asm volatile ( "1: .byte " insn "\n" \
                        "3:\n" \
-- 
2.34.1