[Support] Use zx_cache_flush on Fuchsia to flush instruction cache

Fuchsia doesn't use __clear_cache, instead it provide zx_cache_flush
system call. Use it to flush instruction cache.

Differential Revision: https://reviews.llvm.org/D47753

llvm-svn: 334068
diff --git a/llvm/lib/Support/Unix/Memory.inc b/llvm/lib/Support/Unix/Memory.inc
index cc5a43c..adbfff2 100644
--- a/llvm/lib/Support/Unix/Memory.inc
+++ b/llvm/lib/Support/Unix/Memory.inc
@@ -25,6 +25,10 @@
 #include <mach/mach.h>
 #endif
 
+#ifdef __Fuchsia__
+#include <zircon/syscalls.h>
+#endif
+
 #if defined(__mips__)
 #  if defined(__OpenBSD__)
 #    include <mips64/sysarch.h>
@@ -33,7 +37,7 @@
 #  endif
 #endif
 
-#ifdef __APPLE__
+#if defined(__APPLE__)
 extern "C" void sys_icache_invalidate(const void *Addr, size_t len);
 #else
 extern "C" void __clear_cache(void *, void*);
@@ -206,6 +210,11 @@
   sys_icache_invalidate(const_cast<void *>(Addr), Len);
 #  endif
 
+#elif defined(__Fuchsia__)
+
+  zx_status_t Status = zx_cache_flush(Addr, Len, ZX_CACHE_FLUSH_INSN);
+  assert(Status == ZX_OK && "cannot invalidate instruction cache");
+
 #else
 
 #  if (defined(__POWERPC__) || defined (__ppc__) || \