[PATCH V2] RISC-V: Optimization of vrgather.vv into vrgatherei16.vv[PR111451]

[Li Xu <xuli1@eswincomputing.com>]

From: xuli <xuli1@eswincomputing.com>

Consider this following case:

typedef int32_t vnx32si __attribute__ ((vector_size (128)));

  __attribute__ ((noipa)) void permute_##TYPE (TYPE values1, TYPE values2,     \
					       TYPE *out)                      \
  {                                                                            \
    TYPE v                                                                     \
      = __builtin_shufflevector (values1, values2, MASK_##NUNITS (0, NUNITS)); \
    *(TYPE *) out = v;                                                         \
  }

  T (vnx32si, 32)                                                              \

TEST_ALL (PERMUTE)

Before this patch:
  li	a4,31
  vsetvli	a5,zero,e32,m8,ta,ma
  vl8re32.v	v24,0(a0)
  vid.v	v8
  vrsub.vx	v8,v8,a4
  vrgather.vv	v16,v24,v8
  vs8r.v	v16,0(a2)
  ret

The index vector register "v8" occupies 8 registers.
We should optimize it into vrgatherei16.vv which is
using int16 as the index elements.

After this patch:
  vsetvli	a5,zero,e16,m4,ta,ma
  li	a4,31
  vid.v	v4
  vl8re32.v	v16,0(a0)
  vrsub.vx	v4,v4,a4
  vsetvli	zero,zero,e32,m8,ta,ma
  vrgatherei16.vv	v8,v16,v4
  vs8r.v	v8,0(a2)
  ret
With vrgatherei16.vv, the v8 will occupy 4 registers instead
of 8. Lower the register consuming and register pressure.

	PR target/111451

gcc/ChangeLog:

	* config/riscv/riscv-v.cc (emit_vlmax_gather_insn): Optimization of vrgather.vv into vrgatherei16.vv.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c: Adjust case.
	* gcc.target/riscv/rvv/autovec/vls/perm-4.c: Ditto.
---
 gcc/config/riscv/riscv-v.cc                    | 18 ++++++++++++++++++
 .../riscv/rvv/autovec/vls-vlmax/perm-4.c       |  3 ++-
 .../gcc.target/riscv/rvv/autovec/vls/perm-4.c  |  3 ++-
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/gcc/config/riscv/riscv-v.cc b/gcc/config/riscv/riscv-v.cc
index 64a71a128d4..455efa7ea8a 100644
--- a/gcc/config/riscv/riscv-v.cc
+++ b/gcc/config/riscv/riscv-v.cc
@@ -790,6 +790,24 @@ emit_vlmax_gather_insn (rtx target, rtx op, rtx sel)
       icode = code_for_pred_gather_scalar (data_mode);
       sel = elt;
     }
+  else if (CONST_VECTOR_P (sel)
+           && GET_MODE_BITSIZE (GET_MODE_INNER (sel_mode)) > 16
+           && riscv_get_v_regno_alignment (data_mode) > 1)
+    {
+      /* If the inner mode of data is not QI or HI and data_lmul > 1,
+         emitting vrgatherei16.vv instruction will lower register
+         pressure.
+         data_mode  sel_mode  ei16
+         RVVM1QI    RVVM1QI   RVVM2HI  not needed
+         RVVM2QI    RVVM2QI   RVVM4HI  not needed
+         RVVM2HI    RVVM2HI   RVVM2HI  not needed
+         RVVM2SI    RVVM2SI   RVVM1HI  need
+         RVVM4SI    RVVM4SI   RVVM2HI  need
+         RVVM8DI    RVVM8DI   RVVM2HI  need */
+      PUT_MODE (sel, get_vector_mode (HImode,
+                GET_MODE_NUNITS (data_mode)).require ());
+      icode = code_for_pred_gatherei16 (data_mode);
+    }
   else
     icode = code_for_pred_gather (data_mode);
   rtx ops[] = {target, op, sel};
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c
index 9df69a0cc2c..7ab31043547 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c
@@ -55,6 +55,7 @@
 
 TEST_ALL (PERMUTE)
 
-/* { dg-final { scan-assembler-times {vrgather\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 31 } } */
+/* { dg-final { scan-assembler-times {vrgather\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 19 } } */
+/* { dg-final { scan-assembler-times {vrgatherei16\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 12 } } */
 /* { dg-final { scan-assembler-times {vrsub\.vi} 24 } } */
 /* { dg-final { scan-assembler-times {vrsub\.vx} 7 } } */
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls/perm-4.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls/perm-4.c
index 46cad8ea2f4..4d6862cf1c0 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls/perm-4.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls/perm-4.c
@@ -3,6 +3,7 @@
 
 #include "../vls-vlmax/perm-4.c"
 
-/* { dg-final { scan-assembler-times {vrgather\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 31 } } */
+/* { dg-final { scan-assembler-times {vrgather\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 19 } } */
+/* { dg-final { scan-assembler-times {vrgatherei16\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 12 } } */
 /* { dg-final { scan-assembler-times {vrsub\.vi} 24 } } */
 /* { dg-final { scan-assembler-times {vrsub\.vx} 7 } } */
-- 
2.17.1