[committed 2/6] arc: Fix cached to uncached moves.

[Claudiu Zissulescu via Gcc-patches]

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  <claz...@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  Claudiu Zissulescu  <claz...@synopsys.com>
        Vladimir Isaev <is...@synopsys.com>

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

Signed-off-by: Claudiu Zissulescu <claz...@synopsys.com>
---
 gcc/config/arc/arc.c                      | 12 +++++--
 gcc/testsuite/gcc.target/arc/uncached-9.c | 39 +++++++++++++++++++++++
 2 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/arc/uncached-9.c

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;
+}
-- 
2.26.2