aarch64: Leveraging the use of STP instruction for vec_duplicate

The backend pattern for storing a pair of identical values in 32 and
64-bit modes with the machine instruction STP was missing, and
multiple instructions were needed to reproduce this behavior as a
result of failed RTL pattern match in combine pass.

For the test case:

typedef long long v2di __attribute__((vector_size (16)));
typedef int v2si __attribute__((vector_size (8)));

void
foo (v2di *x, long long a)
{
  v2di tmp = {a, a};
  *x = tmp;
}

void
foo2 (v2si *x, int a)
{
  v2si tmp = {a, a};
  *x = tmp;
}

at -O2 on aarch64 gives:

foo:
    stp x1, x1, [x0]
    ret
foo2:
    stp w1, w1, [x0]
    ret

instead of:

foo:
        dup     v0.2d, x1
        str     q0, [x0]
        ret
foo2:
        dup     v0.2s, w1
        str     d0, [x0]
        ret

Bootstrapped and regtested on aarch64-none-linux-gnu.

gcc/
	* config/aarch64/aarch64-simd.md(aarch64_simd_stp<mode>): New.
	* config/aarch64/constraints.md: Make "Umn" relaxed memory
	constraint.
	* config/aarch64/iterators.md(ldpstp_vel_sz): New.

gcc/testsuite/
	* gcc.target/aarch64/stp_vec_dup_32_64-1.c: New.

4 files changed, 71 insertions, 1 deletions

diff --git a/gcc/config/aarch64/aarch64-simd.md b/gcc/config/aarch64/aarch64-simd.md
index 9f2fce6..cfad812 100644
--- a/gcc/config/aarch64/aarch64-simd.md
+++ b/gcc/config/aarch64/aarch64-simd.md
@@ -257,6 +257,16 @@
   [(set_attr "type" "neon_stp")]
 )
 
+(define_insn "aarch64_simd_stp<mode>"
+  [(set (match_operand:VP_2E 0 "aarch64_mem_pair_lanes_operand" "=Umn,Umn")
+	(vec_duplicate:VP_2E (match_operand:<VEL> 1 "register_operand" "w,r")))]
+  "TARGET_SIMD"
+  "@
+   stp\\t%<Vetype>1, %<Vetype>1, %y0
+   stp\\t%<vw>1, %<vw>1, %y0"
+  [(set_attr "type" "neon_stp, store_<ldpstp_vel_sz>")]
+)
+
 (define_insn "load_pair<VQ:mode><VQ2:mode>"
   [(set (match_operand:VQ 0 "register_operand" "=w")
 	(match_operand:VQ 1 "aarch64_mem_pair_operand" "Ump"))
diff --git a/gcc/config/aarch64/constraints.md b/gcc/config/aarch64/constraints.md
index 5b20abc..6df1dbe 100644
--- a/gcc/config/aarch64/constraints.md
+++ b/gcc/config/aarch64/constraints.md
@@ -287,7 +287,7 @@
 ;; Used for storing or loading pairs in an AdvSIMD register using an STP/LDP
 ;; as a vector-concat.  The address mode uses the same constraints as if it
 ;; were for a single value.
-(define_memory_constraint "Umn"
+(define_relaxed_memory_constraint "Umn"
   "@internal
   A memory address suitable for a load/store pair operation."
   (and (match_code "mem")
diff --git a/gcc/config/aarch64/iterators.md b/gcc/config/aarch64/iterators.md
index 13a7e89..1d0b482 100644
--- a/gcc/config/aarch64/iterators.md
+++ b/gcc/config/aarch64/iterators.md
@@ -1020,6 +1020,9 @@
 ;; Likewise for load/store pair.
 (define_mode_attr ldpstp_sz [(SI "8") (DI "16")])
 
+;; Size of element access for STP/LDP-generated vectors.
+(define_mode_attr ldpstp_vel_sz [(V2SI "8") (V2SF "8") (V2DI "16") (V2DF "16")])
+
 ;; For inequal width int to float conversion
 (define_mode_attr w1 [(HF "w") (SF "w") (DF "x")])
 (define_mode_attr w2 [(HF "x") (SF "x") (DF "w")])
diff --git a/gcc/testsuite/gcc.target/aarch64/stp_vec_dup_32_64-1.c b/gcc/testsuite/gcc.target/aarch64/stp_vec_dup_32_64-1.c
new file mode 100644
index 0000000..fc2c1ea
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/stp_vec_dup_32_64-1.c
@@ -0,0 +1,57 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+typedef long long v2di __attribute__((vector_size (16)));
+typedef int v2si __attribute__((vector_size (8)));
+
+#define TESTV2DI(lab, idx)			\
+  void						\
+  stpv2di_##lab (v2di *x, long long a)		\
+  {						\
+    v2di tmp = {a, a};				\
+    x[idx] = tmp;				\
+  }
+
+
+#define TESTV2SI(lab, idx)			\
+  void						\
+  stpv2si_##lab (v2si *x, int a)		\
+  {						\
+    v2si tmp = {a, a};				\
+    x[idx] = tmp;				\
+  }						\
+
+/* Core test, no imm assembler offset:  */
+
+TESTV2SI(0, 0)
+TESTV2DI(0, 0)
+/* { dg-final { scan-assembler {\s+stp\t(w[0-9]+), \1, \[x[0-9]+\]} } } */
+/* { dg-final { scan-assembler {\s+stp\t(x[0-9]+), \1, \[x[0-9]+\]} } } */
+
+/* Lower offset bounds:  */
+
+/* Vaid offsets:  */
+TESTV2SI(1, -32)
+TESTV2DI(1, -32)
+/* { dg-final { scan-assembler {\s+stp\t(w[0-9]+), \1, \[x[0-9]+, -256\]} } } */
+/* { dg-final { scan-assembler {\s+stp\t(x[0-9]+), \1, \[x[0-9]+, -512\]} } } */
+/* Invalid offsets:  */
+TESTV2SI(2, -33)
+TESTV2DI(2, -33)
+/* { dg-final { scan-assembler-not {\s+stp\t(w[0-9]+), \1, \[x[0-9]+, -264\]} } } */
+/* { dg-final { scan-assembler-not {\s+stp\t(x[0-9]+), \1, \[x[0-9]+, -528\]} } } */
+
+/* Upper offset bounds:   */
+
+/* Valid offsets:  */
+TESTV2SI(3, 31)
+TESTV2DI(3, 31)
+/* { dg-final { scan-assembler {\s+stp\t(w[0-9]+), \1, \[x[0-9]+, 248\]} } } */
+/* { dg-final { scan-assembler {\s+stp\t(x[0-9]+), \1, \[x[0-9]+, 496\]} } } */
+/* Invalid offsets:  */
+TESTV2SI(4, 32)
+TESTV2DI(4, 32)
+/* { dg-final { scan-assembler-not {\s+stp\t(w[0-9]+), \1, \[x[0-9]+, 256\]} } } */
+/* { dg-final { scan-assembler-not {\s+stp\t(x[0-9]+), \1, \[x[0-9]+, 512\]} } } */
+
+