Add support for vectorising live-out values using SVE LASTB
authorRichard Sandiford <richard.sandiford@linaro.org>
Sat, 13 Jan 2018 17:59:50 +0000 (17:59 +0000)
committerRichard Sandiford <rsandifo@gcc.gnu.org>
Sat, 13 Jan 2018 17:59:50 +0000 (17:59 +0000)
This patch uses the SVE LASTB instruction to optimise cases in which
a value produced by the final scalar iteration of a vectorised loop is
live outside the loop.  Previously this situation would stop us from
using a fully-masked loop.

2018-01-13  Richard Sandiford  <richard.sandiford@linaro.org>
    Alan Hayward  <alan.hayward@arm.com>
    David Sherwood  <david.sherwood@arm.com>

gcc/
* doc/md.texi (extract_last_@var{m}): Document.
* optabs.def (extract_last_optab): New optab.
* internal-fn.def (EXTRACT_LAST): New internal function.
* internal-fn.c (cond_unary_direct): New macro.
(expand_cond_unary_optab_fn): Likewise.
(direct_cond_unary_optab_supported_p): Likewise.
* tree-vect-loop.c (vectorizable_live_operation): Allow fully-masked
loops using EXTRACT_LAST.
* config/aarch64/aarch64-sve.md (aarch64_sve_lastb<mode>): Rename to...
(extract_last_<mode>): ...this optab.
(vec_extract<mode><Vel>): Update accordingly.

gcc/testsuite/
* gcc.target/aarch64/sve/live_1.c: New test.
* gcc.target/aarch64/sve/live_1_run.c: Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r256632

gcc/ChangeLog
gcc/config/aarch64/aarch64-sve.md
gcc/doc/md.texi
gcc/internal-fn.c
gcc/internal-fn.def
gcc/optabs.def
gcc/testsuite/ChangeLog
gcc/testsuite/gcc.target/aarch64/sve/live_1.c [new file with mode: 0644]
gcc/testsuite/gcc.target/aarch64/sve/live_1_run.c [new file with mode: 0644]
gcc/tree-vect-loop.c

index 1b52ec1..5216a48 100644 (file)
@@ -2,6 +2,22 @@
            Alan Hayward  <alan.hayward@arm.com>
            David Sherwood  <david.sherwood@arm.com>
 
+       * doc/md.texi (extract_last_@var{m}): Document.
+       * optabs.def (extract_last_optab): New optab.
+       * internal-fn.def (EXTRACT_LAST): New internal function.
+       * internal-fn.c (cond_unary_direct): New macro.
+       (expand_cond_unary_optab_fn): Likewise.
+       (direct_cond_unary_optab_supported_p): Likewise.
+       * tree-vect-loop.c (vectorizable_live_operation): Allow fully-masked
+       loops using EXTRACT_LAST.
+       * config/aarch64/aarch64-sve.md (aarch64_sve_lastb<mode>): Rename to...
+       (extract_last_<mode>): ...this optab.
+       (vec_extract<mode><Vel>): Update accordingly.
+
+2018-01-13  Richard Sandiford  <richard.sandiford@linaro.org>
+           Alan Hayward  <alan.hayward@arm.com>
+           David Sherwood  <david.sherwood@arm.com>
+
        * target.def (empty_mask_is_expensive): New hook.
        * doc/tm.texi.in (TARGET_VECTORIZE_EMPTY_MASK_IS_EXPENSIVE): New hook.
        * doc/tm.texi: Regenerate.
index 0329fed..c451b02 100644 (file)
        /* The last element can be extracted with a LASTB and a false
           predicate.  */
        rtx sel = force_reg (<VPRED>mode, CONST0_RTX (<VPRED>mode));
-       emit_insn (gen_aarch64_sve_lastb<mode> (operands[0], sel,
-                                               operands[1]));
+       emit_insn (gen_extract_last_<mode> (operands[0], sel, operands[1]));
        DONE;
       }
     if (!CONST_INT_P (operands[2]))
        emit_insn (gen_vec_cmp<v_int_equiv><vpred> (sel, cmp, series, zero));
 
        /* Select the element using LASTB.  */
-       emit_insn (gen_aarch64_sve_lastb<mode> (operands[0], sel,
-                                               operands[1]));
+       emit_insn (gen_extract_last_<mode> (operands[0], sel, operands[1]));
        DONE;
       }
   }
 
 ;; Extract the last active element of operand 1 into operand 0.
 ;; If no elements are active, extract the last inactive element instead.
-(define_insn "aarch64_sve_lastb<mode>"
+(define_insn "extract_last_<mode>"
   [(set (match_operand:<VEL> 0 "register_operand" "=r, w")
        (unspec:<VEL>
          [(match_operand:<VPRED> 1 "register_operand" "Upl, Upl")
index 285cffd..f95e7e1 100644 (file)
@@ -5219,6 +5219,14 @@ of a vector of mode @var{m}.  Operand 1 is the vector input and operand 0
 is the scalar result.  The mode of the scalar result is the same as one
 element of @var{m}.
 
+@cindex @code{extract_last_@var{m}} instruction pattern
+@item @code{extract_last_@var{m}}
+Find the last set bit in mask operand 1 and extract the associated element
+of vector operand 2.  Store the result in scalar operand 0.  Operand 2
+has vector mode @var{m} while operand 0 has the mode appropriate for one
+element of @var{m}.  Operand 1 has the usual mask mode for vectors of mode
+@var{m}; see @code{TARGET_VECTORIZE_GET_MASK_MODE}.
+
 @cindex @code{sdot_prod@var{m}} instruction pattern
 @item @samp{sdot_prod@var{m}}
 @cindex @code{udot_prod@var{m}} instruction pattern
index 86a1964..23c9224 100644 (file)
@@ -88,6 +88,7 @@ init_internal_fns ()
 #define mask_store_lanes_direct { 0, 0, false }
 #define unary_direct { 0, 0, true }
 #define binary_direct { 0, 0, true }
+#define cond_unary_direct { 1, 1, true }
 #define cond_binary_direct { 1, 1, true }
 #define while_direct { 0, 2, false }
 
@@ -2886,6 +2887,9 @@ expand_while_optab_fn (internal_fn, gcall *stmt, convert_optab optab)
 #define expand_binary_optab_fn(FN, STMT, OPTAB) \
   expand_direct_optab_fn (FN, STMT, OPTAB, 2)
 
+#define expand_cond_unary_optab_fn(FN, STMT, OPTAB) \
+  expand_direct_optab_fn (FN, STMT, OPTAB, 2)
+
 #define expand_cond_binary_optab_fn(FN, STMT, OPTAB) \
   expand_direct_optab_fn (FN, STMT, OPTAB, 3)
 
@@ -2962,6 +2966,7 @@ multi_vector_optab_supported_p (convert_optab optab, tree_pair types,
 
 #define direct_unary_optab_supported_p direct_optab_supported_p
 #define direct_binary_optab_supported_p direct_optab_supported_p
+#define direct_cond_unary_optab_supported_p direct_optab_supported_p
 #define direct_cond_binary_optab_supported_p direct_optab_supported_p
 #define direct_mask_load_optab_supported_p direct_optab_supported_p
 #define direct_load_lanes_optab_supported_p multi_vector_optab_supported_p
index f098440..fb9f095 100644 (file)
@@ -154,6 +154,10 @@ DEF_INTERNAL_OPTAB_FN (REDUC_IOR, ECF_CONST | ECF_NOTHROW,
 DEF_INTERNAL_OPTAB_FN (REDUC_XOR, ECF_CONST | ECF_NOTHROW,
                       reduc_xor_scal, unary)
 
+/* Extract the last active element from a vector.  */
+DEF_INTERNAL_OPTAB_FN (EXTRACT_LAST, ECF_CONST | ECF_NOTHROW,
+                      extract_last, cond_unary)
+
 /* Unary math functions.  */
 DEF_INTERNAL_FLT_FN (ACOS, ECF_CONST, acos, unary)
 DEF_INTERNAL_FLT_FN (ASIN, ECF_CONST, asin, unary)
index 9a79f4d..6030106 100644 (file)
@@ -307,6 +307,8 @@ OPTAB_D (reduc_and_scal_optab,  "reduc_and_scal_$a")
 OPTAB_D (reduc_ior_scal_optab,  "reduc_ior_scal_$a")
 OPTAB_D (reduc_xor_scal_optab,  "reduc_xor_scal_$a")
 
+OPTAB_D (extract_last_optab, "extract_last_$a")
+
 OPTAB_D (sdot_prod_optab, "sdot_prod$I$a")
 OPTAB_D (ssum_widen_optab, "widen_ssum$I$a3")
 OPTAB_D (udot_prod_optab, "udot_prod$I$a")
index 55e58c2..60109a1 100644 (file)
@@ -2,6 +2,13 @@
            Alan Hayward  <alan.hayward@arm.com>
            David Sherwood  <david.sherwood@arm.com>
 
+       * gcc.target/aarch64/sve/live_1.c: New test.
+       * gcc.target/aarch64/sve/live_1_run.c: Likewise.
+
+2018-01-13  Richard Sandiford  <richard.sandiford@linaro.org>
+           Alan Hayward  <alan.hayward@arm.com>
+           David Sherwood  <david.sherwood@arm.com>
+
        * gcc.target/aarch64/sve/nopeel_1.c: New test.
        * gcc.target/aarch64/sve/peel_ind_1.c: Likewise.
        * gcc.target/aarch64/sve/peel_ind_1_run.c: Likewise.
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/live_1.c b/gcc/testsuite/gcc.target/aarch64/sve/live_1.c
new file mode 100644 (file)
index 0000000..e8d92ec
--- /dev/null
@@ -0,0 +1,41 @@
+/* { dg-do assemble { target aarch64_asm_sve_ok } } */
+/* { dg-options "-O2 -ftree-vectorize --save-temps" } */
+
+#include <stdint.h>
+
+#define EXTRACT_LAST(TYPE)                     \
+  TYPE __attribute__ ((noinline, noclone))     \
+  test_##TYPE (TYPE *x, int n, TYPE value)     \
+  {                                            \
+    TYPE last;                                 \
+    for (int j = 0; j < n; ++j)                        \
+      {                                                \
+       last = x[j];                            \
+       x[j] = last * value;                    \
+      }                                                \
+    return last;                               \
+  }
+
+#define TEST_ALL(T)                            \
+  T (uint8_t)                                  \
+  T (uint16_t)                                 \
+  T (uint32_t)                                 \
+  T (uint64_t)                                 \
+  T (_Float16)                                 \
+  T (float)                                    \
+  T (double)
+
+TEST_ALL (EXTRACT_LAST)
+
+/* { dg-final { scan-assembler-times {\twhilelo\tp[0-7].b, } 2 } } */
+/* { dg-final { scan-assembler-times {\twhilelo\tp[0-7].h, } 4 } } */
+/* { dg-final { scan-assembler-times {\twhilelo\tp[0-7].s, } 4 } } */
+/* { dg-final { scan-assembler-times {\twhilelo\tp[0-7].d, } 4 } } */
+
+/* { dg-final { scan-assembler-times {\tlastb\tw[0-9]+, p[0-7], z[0-9]+\.b\n} 1 } } */
+/* { dg-final { scan-assembler-times {\tlastb\tw[0-9]+, p[0-7], z[0-9]+\.h\n} 1 } } */
+/* { dg-final { scan-assembler-times {\tlastb\tw[0-9]+, p[0-7], z[0-9]+\.s\n} 1 } } */
+/* { dg-final { scan-assembler-times {\tlastb\tx[0-9]+, p[0-7], z[0-9]+\.d\n} 1 } } */
+/* { dg-final { scan-assembler-times {\tlastb\th[0-9]+, p[0-7], z[0-9]+\.h\n} 1 } } */
+/* { dg-final { scan-assembler-times {\tlastb\ts[0-9]+, p[0-7], z[0-9]+\.s\n} 1 } } */
+/* { dg-final { scan-assembler-times {\tlastb\td[0-9]+, p[0-7], z[0-9]+\.d\n} 1 } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/live_1_run.c b/gcc/testsuite/gcc.target/aarch64/sve/live_1_run.c
new file mode 100644 (file)
index 0000000..e4308a5
--- /dev/null
@@ -0,0 +1,35 @@
+/* { dg-do run { target { aarch64_sve_hw } } } */
+/* { dg-options "-O2 -ftree-vectorize -fno-inline" } */
+
+#include "live_1.c"
+
+#define N 107
+#define OP 70
+
+#define TEST_LOOP(TYPE)                                \
+  {                                            \
+    TYPE a[N];                                 \
+    for (int i = 0; i < N; ++i)                        \
+      {                                                \
+       a[i] = i * 2 + (i % 3);                 \
+       asm volatile ("" ::: "memory");         \
+      }                                                \
+    TYPE expected = a[N - 1];                  \
+    TYPE res = test_##TYPE (a, N, OP);         \
+    if (res != expected)                       \
+      __builtin_abort ();                      \
+    for (int i = 0; i < N; ++i)                        \
+      {                                                \
+       TYPE old = i * 2 + (i % 3);             \
+       if (a[i] != (TYPE) (old * (TYPE) OP))   \
+         __builtin_abort ();                   \
+       asm volatile ("" ::: "memory");         \
+      }                                                \
+  }
+
+int __attribute__ ((optimize (1)))
+main (void)
+{
+  TEST_ALL (TEST_LOOP);
+  return 0;
+}
index d7cc12f..59cd1c4 100644 (file)
@@ -7812,16 +7812,43 @@ vectorizable_live_operation (gimple *stmt,
 
   if (!vec_stmt)
     {
+      /* No transformation required.  */
       if (LOOP_VINFO_CAN_FULLY_MASK_P (loop_vinfo))
        {
-         if (dump_enabled_p ())
-           dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
-                            "can't use a fully-masked loop because "
-                            "a value is live outside the loop.\n");
-         LOOP_VINFO_CAN_FULLY_MASK_P (loop_vinfo) = false;
+         if (!direct_internal_fn_supported_p (IFN_EXTRACT_LAST, vectype,
+                                              OPTIMIZE_FOR_SPEED))
+           {
+             if (dump_enabled_p ())
+               dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+                                "can't use a fully-masked loop because "
+                                "the target doesn't support extract last "
+                                "reduction.\n");
+             LOOP_VINFO_CAN_FULLY_MASK_P (loop_vinfo) = false;
+           }
+         else if (slp_node)
+           {
+             if (dump_enabled_p ())
+               dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+                                "can't use a fully-masked loop because an "
+                                "SLP statement is live after the loop.\n");
+             LOOP_VINFO_CAN_FULLY_MASK_P (loop_vinfo) = false;
+           }
+         else if (ncopies > 1)
+           {
+             if (dump_enabled_p ())
+               dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+                                "can't use a fully-masked loop because"
+                                " ncopies is greater than 1.\n");
+             LOOP_VINFO_CAN_FULLY_MASK_P (loop_vinfo) = false;
+           }
+         else
+           {
+             gcc_assert (ncopies == 1 && !slp_node);
+             vect_record_loop_mask (loop_vinfo,
+                                    &LOOP_VINFO_MASKS (loop_vinfo),
+                                    1, vectype);
+           }
        }
-
-      /* No transformation required.  */
       return true;
     }
 
@@ -7838,12 +7865,12 @@ vectorizable_live_operation (gimple *stmt,
             : TYPE_SIZE (TREE_TYPE (vectype)));
   vec_bitsize = TYPE_SIZE (vectype);
 
-  gcc_assert (!LOOP_VINFO_FULLY_MASKED_P (loop_vinfo));
-
   /* Get the vectorized lhs of STMT and the lane to use (counted in bits).  */
   tree vec_lhs, bitstart;
   if (slp_node)
     {
+      gcc_assert (!LOOP_VINFO_FULLY_MASKED_P (loop_vinfo));
+
       /* Get the correct slp vectorized stmt.  */
       vec_lhs = gimple_get_lhs (SLP_TREE_VEC_STMTS (slp_node)[vec_entry]);
 
@@ -7855,6 +7882,8 @@ vectorizable_live_operation (gimple *stmt,
     {
       enum vect_def_type dt = STMT_VINFO_DEF_TYPE (stmt_info);
       vec_lhs = vect_get_vec_def_for_operand_1 (stmt, dt);
+      gcc_checking_assert (ncopies == 1
+                          || !LOOP_VINFO_FULLY_MASKED_P (loop_vinfo));
 
       /* For multiple copies, get the last copy.  */
       for (int i = 1; i < ncopies; ++i)
@@ -7865,15 +7894,39 @@ vectorizable_live_operation (gimple *stmt,
       bitstart = int_const_binop (MINUS_EXPR, vec_bitsize, bitsize);
     }
 
-  /* Create a new vectorized stmt for the uses of STMT and insert outside the
-     loop.  */
   gimple_seq stmts = NULL;
-  tree bftype = TREE_TYPE (vectype);
-  if (VECTOR_BOOLEAN_TYPE_P (vectype))
-    bftype = build_nonstandard_integer_type (tree_to_uhwi (bitsize), 1);
-  tree new_tree = build3 (BIT_FIELD_REF, bftype, vec_lhs, bitsize, bitstart);
-  new_tree = force_gimple_operand (fold_convert (lhs_type, new_tree), &stmts,
-                                  true, NULL_TREE);
+  tree new_tree;
+  if (LOOP_VINFO_FULLY_MASKED_P (loop_vinfo))
+    {
+      /* Emit:
+
+          SCALAR_RES = EXTRACT_LAST <VEC_LHS, MASK>
+
+        where VEC_LHS is the vectorized live-out result and MASK is
+        the loop mask for the final iteration.  */
+      gcc_assert (ncopies == 1 && !slp_node);
+      tree scalar_type = TREE_TYPE (STMT_VINFO_VECTYPE (stmt_info));
+      tree scalar_res = make_ssa_name (scalar_type);
+      tree mask = vect_get_loop_mask (gsi, &LOOP_VINFO_MASKS (loop_vinfo),
+                                     1, vectype, 0);
+      gcall *new_stmt = gimple_build_call_internal (IFN_EXTRACT_LAST,
+                                                   2, mask, vec_lhs);
+      gimple_call_set_lhs (new_stmt, scalar_res);
+      gimple_seq_add_stmt (&stmts, new_stmt);
+
+      /* Convert the extracted vector element to the required scalar type.  */
+      new_tree = gimple_convert (&stmts, lhs_type, scalar_res);
+    }
+  else
+    {
+      tree bftype = TREE_TYPE (vectype);
+      if (VECTOR_BOOLEAN_TYPE_P (vectype))
+       bftype = build_nonstandard_integer_type (tree_to_uhwi (bitsize), 1);
+      new_tree = build3 (BIT_FIELD_REF, bftype, vec_lhs, bitsize, bitstart);
+      new_tree = force_gimple_operand (fold_convert (lhs_type, new_tree),
+                                      &stmts, true, NULL_TREE);
+    }
+
   if (stmts)
     gsi_insert_seq_on_edge_immediate (single_exit (loop), stmts);