> 
> Hmmm these patterns are identical in what they match they just have the
> effect of printing operands 1 and 2 in a different order.
> Perhaps it's more compact to change the output template into a
> BYTES_BIG_ENDIAN ?
> "uzp1\\t%0.<V2ntype>, %1.<V2ntype>, %2.<V2ntype>"" :
> uzp1\\t%0.<V2ntype>, %2.<V2ntype>, %1.<V2ntype>"
> and avoid having a second at all?
> 

Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.

Ok for master?

Thanks,
Tamar

gcc/ChangeLog:

	* config/aarch64/aarch64-simd.md (*aarch64_narrow_trunc<mode>): New.
	* config/aarch64/iterators.md (VNARROWSIMD, Vnarrowsimd): New.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/narrow_high_combine.c: Update case.
	* gcc.target/aarch64/xtn-combine-1.c: New test.
	* gcc.target/aarch64/xtn-combine-2.c: New test.
	* gcc.target/aarch64/xtn-combine-3.c: New test.
	* gcc.target/aarch64/xtn-combine-4.c: New test.
	* gcc.target/aarch64/xtn-combine-5.c: New test.
	* gcc.target/aarch64/xtn-combine-6.c: New test.

--- inline copy of patch ---

diff --git a/gcc/config/aarch64/aarch64-simd.md b/gcc/config/aarch64/aarch64-simd.md
index 0b340b49fa06684b80d0b78cb712e49328ca92d5..b0dda554466149817a7828dbf4e0ed372a91872b 100644
--- a/gcc/config/aarch64/aarch64-simd.md
+++ b/gcc/config/aarch64/aarch64-simd.md
@@ -1753,6 +1753,23 @@ (define_expand "aarch64_xtn2<mode>"
   }
 )
 
+(define_insn "*aarch64_narrow_trunc<mode>"
+  [(set (match_operand:<VNARROWQ2> 0 "register_operand" "=w")
+	(vec_concat:<VNARROWQ2>
+          (truncate:<VNARROWQ>
+            (match_operand:VQN 1 "register_operand" "w"))
+	  (truncate:<VNARROWQ>
+	    (match_operand:VQN 2 "register_operand" "w"))))]
+  "TARGET_SIMD"
+{
+  if (!BYTES_BIG_ENDIAN)
+    return "uzp1\\t%0.<V2ntype>, %1.<V2ntype>, %2.<V2ntype>";
+  else
+    return "uzp1\\t%0.<V2ntype>, %2.<V2ntype>, %1.<V2ntype>";
+}
+  [(set_attr "type" "neon_permute<q>")]
+)
+
 ;; Packing doubles.
 
 (define_expand "vec_pack_trunc_<mode>"
diff --git a/gcc/config/aarch64/iterators.md b/gcc/config/aarch64/iterators.md
index 8dbeed3b0d4a44cdc17dd333ed397b39a33f386a..95b385c0c9405fe95fcd07262a9471ab13d5488e 100644
--- a/gcc/config/aarch64/iterators.md
+++ b/gcc/config/aarch64/iterators.md
@@ -270,6 +270,14 @@ (define_mode_iterator VDQHS [V4HI V8HI V2SI V4SI])
 ;; Advanced SIMD modes for H, S and D types.
 (define_mode_iterator VDQHSD [V4HI V8HI V2SI V4SI V2DI])
 
+;; Modes for which we can narrow the element and increase the lane counts
+;; to preserve the same register size.
+(define_mode_attr VNARROWSIMD [(V4HI "V8QI") (V8HI "V16QI") (V4SI "V8HI")
+			       (V2SI "V4HI") (V2DI "V4SI")])
+
+(define_mode_attr Vnarrowsimd [(V4HI "v8qi") (V8HI "v16qi") (V4SI "v8hi")
+			       (V2SI "v4hi") (V2DI "v4si")])
+
 ;; Advanced SIMD and scalar integer modes for H and S.
 (define_mode_iterator VSDQ_HSI [V4HI V8HI V2SI V4SI HI SI])
 
diff --git a/gcc/testsuite/gcc.target/aarch64/narrow_high_combine.c b/gcc/testsuite/gcc.target/aarch64/narrow_high_combine.c
index 50ecab002a3552d37a5cc0d8921f42f6c3dba195..fa61196d3644caa48b12151e12b15dfeab8c7e71 100644
--- a/gcc/testsuite/gcc.target/aarch64/narrow_high_combine.c
+++ b/gcc/testsuite/gcc.target/aarch64/narrow_high_combine.c
@@ -225,7 +225,8 @@ TEST_2_UNARY (vqmovun, uint32x4_t, int64x2_t, s64, u32)
 /* { dg-final { scan-assembler-times "\\tuqshrn2\\tv" 6} }  */
 /* { dg-final { scan-assembler-times "\\tsqrshrn2\\tv" 6} }  */
 /* { dg-final { scan-assembler-times "\\tuqrshrn2\\tv" 6} }  */
-/* { dg-final { scan-assembler-times "\\txtn2\\tv" 12} }  */
+/* { dg-final { scan-assembler-times "\\txtn2\\tv" 6} }  */
+/* { dg-final { scan-assembler-times "\\tuzp1\\tv" 6} }  */
 /* { dg-final { scan-assembler-times "\\tuqxtn2\\tv" 6} }  */
 /* { dg-final { scan-assembler-times "\\tsqxtn2\\tv" 6} }  */
 /* { dg-final { scan-assembler-times "\\tsqxtun2\\tv" 6} }  */
diff --git a/gcc/testsuite/gcc.target/aarch64/xtn-combine-1.c b/gcc/testsuite/gcc.target/aarch64/xtn-combine-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..14e0414cd1478f1cb7b17766aa8d4451c5659977
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/xtn-combine-1.c
@@ -0,0 +1,16 @@
+/* { dg-do assemble } */
+/* { dg-options "-O3 --save-temps --param=vect-epilogues-nomask=0" } */
+
+#define SIGN signed
+#define TYPE1 char
+#define TYPE2 short
+
+void d2 (SIGN TYPE1 * restrict a, SIGN TYPE2 *b, int n)
+{
+    for (int i = 0; i < n; i++)
+      a[i] = b[i];
+}
+
+/* { dg-final { scan-assembler-times {\tuzp1\t} 1 } } */
+/* { dg-final { scan-assembler-not {\txtn\t} } } */
+/* { dg-final { scan-assembler-not {\txtn2\t} } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/xtn-combine-2.c b/gcc/testsuite/gcc.target/aarch64/xtn-combine-2.c
new file mode 100644
index 0000000000000000000000000000000000000000..c259010442bca4ba008706e47b3ffcc50a910b52
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/xtn-combine-2.c
@@ -0,0 +1,16 @@
+/* { dg-do assemble } */
+/* { dg-options "-O3 --save-temps --param=vect-epilogues-nomask=0" } */
+
+#define SIGN signed
+#define TYPE1 short
+#define TYPE2 int
+
+void d2 (SIGN TYPE1 * restrict a, SIGN TYPE2 *b, int n)
+{
+    for (int i = 0; i < n; i++)
+      a[i] = b[i];
+}
+
+/* { dg-final { scan-assembler-times {\tuzp1\t} 1 } } */
+/* { dg-final { scan-assembler-not {\txtn\t} } } */
+/* { dg-final { scan-assembler-not {\txtn2\t} } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/xtn-combine-3.c b/gcc/testsuite/gcc.target/aarch64/xtn-combine-3.c
new file mode 100644
index 0000000000000000000000000000000000000000..9a2065f65101f82ebe33519840919f9606192c43
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/xtn-combine-3.c
@@ -0,0 +1,16 @@
+/* { dg-do assemble } */
+/* { dg-options "-O3 --save-temps --param=vect-epilogues-nomask=0" } */
+
+#define SIGN signed
+#define TYPE1 int
+#define TYPE2 long long
+
+void d2 (SIGN TYPE1 * restrict a, SIGN TYPE2 *b, int n)
+{
+    for (int i = 0; i < n; i++)
+      a[i] = b[i];
+}
+
+/* { dg-final { scan-assembler-times {\tuzp1\t} 1 } } */
+/* { dg-final { scan-assembler-not {\txtn\t} } } */
+/* { dg-final { scan-assembler-not {\txtn2\t} } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/xtn-combine-4.c b/gcc/testsuite/gcc.target/aarch64/xtn-combine-4.c
new file mode 100644
index 0000000000000000000000000000000000000000..77c3dce12049989d344e4652bd593de2e846ae25
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/xtn-combine-4.c
@@ -0,0 +1,16 @@
+/* { dg-do assemble } */
+/* { dg-options "-O3 --save-temps --param=vect-epilogues-nomask=0" } */
+
+#define SIGN unsigned
+#define TYPE1 char
+#define TYPE2 short
+
+void d2 (SIGN TYPE1 * restrict a, SIGN TYPE2 *b, int n)
+{
+    for (int i = 0; i < n; i++)
+      a[i] = b[i];
+}
+
+/* { dg-final { scan-assembler-times {\tuzp1\t} 1 } } */
+/* { dg-final { scan-assembler-not {\txtn\t} } } */
+/* { dg-final { scan-assembler-not {\txtn2\t} } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/xtn-combine-5.c b/gcc/testsuite/gcc.target/aarch64/xtn-combine-5.c
new file mode 100644
index 0000000000000000000000000000000000000000..ae30e864ed7a239c40522423d7493ddd33830cc8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/xtn-combine-5.c
@@ -0,0 +1,16 @@
+/* { dg-do assemble } */
+/* { dg-options "-O3 --save-temps --param=vect-epilogues-nomask=0" } */
+
+#define SIGN unsigned
+#define TYPE1 short
+#define TYPE2 int
+
+void d2 (SIGN TYPE1 * restrict a, SIGN TYPE2 *b, int n)
+{
+    for (int i = 0; i < n; i++)
+      a[i] = b[i];
+}
+
+/* { dg-final { scan-assembler-times {\tuzp1\t} 1 } } */
+/* { dg-final { scan-assembler-not {\txtn\t} } } */
+/* { dg-final { scan-assembler-not {\txtn2\t} } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/xtn-combine-6.c b/gcc/testsuite/gcc.target/aarch64/xtn-combine-6.c
new file mode 100644
index 0000000000000000000000000000000000000000..882f3d333e2cc42e964d880de5b58c505ec8b122
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/xtn-combine-6.c
@@ -0,0 +1,16 @@
+/* { dg-do assemble } */
+/* { dg-options "-O3 --save-temps --param=vect-epilogues-nomask=0" } */
+
+#define SIGN unsigned
+#define TYPE1 int
+#define TYPE2 long long
+
+void d2 (SIGN TYPE1 * restrict a, SIGN TYPE2 *b, int n)
+{
+    for (int i = 0; i < n; i++)
+      a[i] = b[i];
+}
+
+/* { dg-final { scan-assembler-times {\tuzp1\t} 1 } } */
+/* { dg-final { scan-assembler-not {\txtn\t} } } */
+/* { dg-final { scan-assembler-not {\txtn2\t} } } */