[PATCH] [x86] Fix unrecognizable insn due to illegal immediate_operand (const_int 255) of QImode.

[liuhongt <hongtao.liu@intel.com>]

For __builtin_ia32_vec_set_v16qi (a, -1, 2) with
!flag_signed_char. it's transformed to
__builtin_ia32_vec_set_v16qi (_4, 255, 2) in the gimple,
and expanded to (const_int 255) in the rtl. But for immediate_operand,
it expects (const_int 255) to be signed extended to
(const_int -1). The mismatch caused an unrecognizable insn error.

expand_expr_real_1 generates (const_int 255) without considering the target mode.
I guess it's on purpose, so I'll leave that alone and only change the expander
in the backend. After applying convert_modes to (const_int 255),
it's transformed to (const_int -1) which fix the issue.

Bootstrapped and regtested x86_64-pc-linux-gnu{-m32,}.
Ok for trunk(and backport to GCC-10/11/12 release branches)?

gcc/ChangeLog:

	PR target/107863
	* config/i386/i386-expand.cc (ix86_expand_vec_set_builtin):
	Convert op1 to target mode whenever mode mismatch.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr107863.c: New test.
---
 gcc/config/i386/i386-expand.cc           | 2 +-
 gcc/testsuite/gcc.target/i386/pr107863.c | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr107863.c

diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index 0373c3614a4..c639ee3a9f7 100644
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -12475,7 +12475,7 @@ ix86_expand_vec_set_builtin (tree exp)
   op1 = expand_expr (arg1, NULL_RTX, mode1, EXPAND_NORMAL);
   elt = get_element_number (TREE_TYPE (arg0), arg2);
 
-  if (GET_MODE (op1) != mode1 && GET_MODE (op1) != VOIDmode)
+  if (GET_MODE (op1) != mode1)
     op1 = convert_modes (mode1, GET_MODE (op1), op1, true);
 
   op0 = force_reg (tmode, op0);
diff --git a/gcc/testsuite/gcc.target/i386/pr107863.c b/gcc/testsuite/gcc.target/i386/pr107863.c
new file mode 100644
index 00000000000..99fd85d9765
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr107863.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-mavx2 -O" } */
+
+typedef char v16qi __attribute__((vector_size(16)));
+
+v16qi foo(v16qi a){
+  return __builtin_ia32_vec_set_v16qi (a, -1, 2);
+}
-- 
2.27.0