arc: Fix cached to uncached moves.

We need an temporary register when moving data from a cached memory to
an uncached memory. Fix this issue and add a test for it.

gcc/
2020-12-29  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.c (prepare_move_operands): Use a temporary
	registers when we have cached mem-to-uncached mem moves.

gcc/testsuite/
2020-12-29  Vladimir Isaev  <isaev@synopsys.com>

	* gcc.target/arc/uncached-9.c: New test.

Signed-off-by: Claudiu Zissulescu <claziss@synopsys.com>

2 files changed, 49 insertions, 2 deletions

diff --git a/gcc/config/arc/arc.c b/gcc/config/arc/arc.c
index 6a9e1fbf824..d0a52ee8b8d 100644
--- a/gcc/config/arc/arc.c
+++ b/gcc/config/arc/arc.c
@@ -9234,13 +9234,21 @@ prepare_move_operands (rtx *operands, machine_mode mode)
 	}
       if (arc_is_uncached_mem_p (operands[1]))
 	{
+	  rtx tmp = operands[0];
+
 	  if (MEM_P (operands[0]))
-	    operands[0] = force_reg (mode, operands[0]);
+	    tmp = gen_reg_rtx (mode);
+
 	  emit_insn (gen_rtx_SET
-		     (operands[0],
+		     (tmp,
 		      gen_rtx_UNSPEC_VOLATILE
 		      (mode, gen_rtvec (1, operands[1]),
 		       VUNSPEC_ARC_LDDI)));
+	  if (MEM_P (operands[0]))
+	    {
+	      operands[1] = tmp;
+	      return false;
+	    }
 	  return true;
 	}
     }
diff --git a/gcc/testsuite/gcc.target/arc/uncached-9.c b/gcc/testsuite/gcc.target/arc/uncached-9.c
new file mode 100644
index 00000000000..4caba293bc5
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arc/uncached-9.c
@@ -0,0 +1,39 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#include <stdlib.h>
+
+struct uncached_st
+{
+  int value;
+} __attribute__((uncached));
+
+struct cached_st
+{
+  int value;
+};
+
+struct uncached_st g_uncached_st =
+  {
+    .value = 17
+  };
+
+struct cached_st g_cached_st =
+  {
+    .value = 4
+  };
+
+void __attribute__((noinline)) test_struct_copy (void)
+{
+  g_cached_st.value = g_uncached_st.value;
+}
+
+int main (void)
+{
+  test_struct_copy();
+
+  if (g_cached_st.value != g_uncached_st.value)
+    abort ();
+
+  return 0;
+}