[PATCH v4] Mode-Switching: Fix SET_SRC ICE for create_pre_exit

[pan2.li@intel.com]

From: Pan Li <pan2.li@intel.com>

In same cases, like gcc/testsuite/gcc.dg/pr78148.c in RISC-V, there will
be only 1 operand when SET_SRC in create_pre_exit. For example as below.

(insn 13 9 14 2 (clobber (reg/i:TI 10 a0)) "gcc/testsuite/gcc.dg/pr78148.c":24:1 -1
  (expr_list:REG_UNUSED (reg/i:TI 10 a0)
    (nil)))

Unfortunately, SET_SRC requires at least 2 operands and then Segment
Fault here. For SH4 part result in Segment Fault, it looks like only
valid when the return_copy_pat is load or something like that. Thus,
this patch try to fix it by restrict the SET insn for SET_SRC.

Signed-off-by: Pan Li <pan2.li@intel.com>

gcc/ChangeLog:

	* mode-switching.cc (create_pre_exit): Add SET insn check.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/mode-switch-ice-1.c: New test.
---
 gcc/mode-switching.cc                         |  1 +
 .../gcc.target/riscv/mode-switch-ice-1.c      | 22 +++++++++++++++++++
 2 files changed, 23 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/riscv/mode-switch-ice-1.c

diff --git a/gcc/mode-switching.cc b/gcc/mode-switching.cc
index 64ae2bc29c3..f483c831c35 100644
--- a/gcc/mode-switching.cc
+++ b/gcc/mode-switching.cc
@@ -411,6 +411,7 @@ create_pre_exit (int n_entities, int *entity_map, const int *num_modes)
 			   conflict with address reloads.  */
 			if (copy_start >= ret_start
 			    && copy_start + copy_num <= ret_end
+			    && GET_CODE (return_copy_pat) == SET
 			    && OBJECT_P (SET_SRC (return_copy_pat)))
 			  forced_late_switch = true;
 			break;
diff --git a/gcc/testsuite/gcc.target/riscv/mode-switch-ice-1.c b/gcc/testsuite/gcc.target/riscv/mode-switch-ice-1.c
new file mode 100644
index 00000000000..1b34a471904
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/mode-switch-ice-1.c
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+struct A { char e, f; };
+
+struct B
+{
+  int g;
+  struct A h[4];
+};
+
+extern void bar (int, int);
+
+struct B foo (void)
+{
+  bar (2, 1);
+}
+
+void baz ()
+{
+  foo ();
+}
-- 
2.34.1