https://gcc.gnu.org/g:bb46d05ad64e4e0acb3307e76bab340aa8587d3e

commit r15-5756-gbb46d05ad64e4e0acb3307e76bab340aa8587d3e
Author: Mariam Arutunian <mariamarutun...@gmail.com>
Date:   Mon Nov 11 12:48:34 2024 -0700

    [PATCH v6 01/12] Implement internal functions for efficient CRC computation.
    
    Add two new internal functions (IFN_CRC, IFN_CRC_REV), to provide faster
    CRC generation.
    One performs bit-forward and the other bit-reversed CRC computation.
    If CRC optabs are supported, they are used for the CRC computation.
    Otherwise, table-based CRC is generated.
    The supported data and CRC sizes are 8, 16, 32, and 64 bits.
    The polynomial is without the leading 1.
    A table with 256 elements is used to store precomputed CRCs.
    For the reflection of inputs and the output, a simple algorithm involving
    SHIFT, AND, and OR operations is used.
    
    gcc/
    
            * doc/md.texi (crc@var{m}@var{n}4, crc_rev@var{m}@var{n}4): 
Document.
            * expr.cc (calculate_crc): New function.
            (assemble_crc_table): Likewise.
            (generate_crc_table): Likewise.
            (calculate_table_based_CRC): Likewise.
            (expand_crc_table_based): Likewise.
            (gen_common_operation_to_reflect): Likewise.
            (reflect_64_bit_value): Likewise.
            (reflect_32_bit_value): Likewise.
            (reflect_16_bit_value): Likewise.
            (reflect_8_bit_value): Likewise.
            (generate_reflecting_code_standard): Likewise.
            (expand_reversed_crc_table_based): Likewise.
            * expr.h (generate_reflecting_code_standard): New function 
declaration.
            (expand_crc_table_based): Likewise.
            (expand_reversed_crc_table_based): Likewise.
            * internal-fn.cc: (crc_direct): Define.
            (direct_crc_optab_supported_p): Likewise.
            (expand_crc_optab_fn): New function
            * internal-fn.def (CRC, CRC_REV): New internal functions.
            * optabs.def (crc_optab, crc_rev_optab): New optabs.
    
            Signed-off-by: Mariam Arutunian <mariamarutun...@gmail.com>
            Co-authored-by: Joern Rennecke <joern.renne...@embecosm.com>
            Co-authored-by: Jeff Law <j...@ventanamicro.com>

Diff:
---
 gcc/doc/md.texi     |  14 +++
 gcc/expr.cc         | 347 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 gcc/expr.h          |   6 +
 gcc/internal-fn.cc  |  75 ++++++++++++
 gcc/internal-fn.def |   2 +
 gcc/optabs.def      |   2 +
 6 files changed, 446 insertions(+)

diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index c4c37053833e..69605bf75c0f 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -8578,6 +8578,20 @@ Return 1 if operand 1 is a normal floating point number 
and 0
 otherwise.  @var{m} is a scalar floating point mode.  Operand 0
 has mode @code{SImode}, and operand 1 has mode @var{m}.
 
+@cindex @code{crc@var{m}@var{n}4} instruction pattern
+@item @samp{crc@var{m}@var{n}4}
+Calculate a bit-forward CRC using operands 1, 2 and 3,
+then store the result in operand 0.
+Operands 1 is the initial CRC, operands 2 is the data and operands 3 is the
+polynomial without leading 1.
+Operands 0, 1 and 3 have mode @var{n} and operand 2 has mode @var{m}, where
+both modes are integers.  The size of CRC to be calculated is determined by the
+mode; for example, if @var{n} is @code{HImode}, a CRC16 is calculated.
+
+@cindex @code{crc_rev@var{m}@var{n}4} instruction pattern
+@item @samp{crc_rev@var{m}@var{n}4}
+Similar to @samp{crc@var{m}@var{n}4}, but calculates a bit-reversed CRC.
+
 @end table
 
 @end ifset
diff --git a/gcc/expr.cc b/gcc/expr.cc
index f4939140bb51..de25437660e0 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -14177,3 +14177,350 @@ int_expr_size (const_tree exp)
 
   return tree_to_shwi (size);
 }
+
+/* Calculate CRC for the initial CRC and given POLYNOMIAL.
+   CRC_BITS is CRC size.  */
+
+static unsigned HOST_WIDE_INT
+calculate_crc (unsigned HOST_WIDE_INT crc,
+              unsigned HOST_WIDE_INT polynomial,
+              unsigned short crc_bits)
+{
+  unsigned HOST_WIDE_INT msb = HOST_WIDE_INT_1U << (crc_bits - 1);
+  crc = crc << (crc_bits - 8);
+  for (short i = 8; i > 0; --i)
+    {
+      if (crc & msb)
+       crc = (crc << 1) ^ polynomial;
+      else
+       crc <<= 1;
+    }
+  /* Zero out bits in crc beyond the specified number of crc_bits.  */
+  if (crc_bits < sizeof (crc) * CHAR_BIT)
+    crc &= (HOST_WIDE_INT_1U << crc_bits) - 1;
+  return crc;
+}
+
+/* Assemble CRC table with 256 elements for the given POLYNOM and CRC_BITS with
+   given ID.
+   ID is the identifier of the table, the name of the table is unique,
+   contains CRC size and the polynomial.
+   POLYNOM is the polynomial used to calculate the CRC table's elements.
+   CRC_BITS is the size of CRC, may be 8, 16, ... . */
+
+rtx
+assemble_crc_table (tree id, unsigned HOST_WIDE_INT polynom,
+                   unsigned short crc_bits)
+{
+  unsigned table_el_n = 0x100;
+  tree ar = build_array_type (make_unsigned_type (crc_bits),
+                             build_index_type (size_int (table_el_n - 1)));
+  tree decl = build_decl (UNKNOWN_LOCATION, VAR_DECL, id, ar);
+  SET_DECL_ASSEMBLER_NAME (decl, id);
+  DECL_ARTIFICIAL (decl) = 1;
+  rtx tab = gen_rtx_SYMBOL_REF (Pmode, IDENTIFIER_POINTER (id));
+  TREE_ASM_WRITTEN (decl) = 0;
+
+  /* Initialize the table.  */
+  vec<tree, va_gc> *initial_values;
+  vec_alloc (initial_values, table_el_n);
+  for (size_t i = 0; i < table_el_n; ++i)
+    {
+      unsigned HOST_WIDE_INT crc = calculate_crc (i, polynom, crc_bits);
+      tree element = build_int_cstu (make_unsigned_type (crc_bits), crc);
+      vec_safe_push (initial_values, element);
+    }
+  DECL_INITIAL (decl) = build_constructor_from_vec (ar, initial_values);
+
+  TREE_READONLY (decl) = 1;
+  TREE_STATIC (decl) = 1;
+
+  if (TREE_PUBLIC (id))
+    {
+      TREE_PUBLIC (decl) = 1;
+      make_decl_one_only (decl, DECL_ASSEMBLER_NAME (decl));
+    }
+
+  mark_decl_referenced (decl);
+  varpool_node::finalize_decl (decl);
+
+  return tab;
+}
+
+/* Generate CRC lookup table by calculating CRC for all possible
+   8-bit data values.  The table is stored with a specific name in the 
read-only
+   static data section.
+   POLYNOM is the polynomial used to calculate the CRC table's elements.
+   CRC_BITS is the size of CRC, may be 8, 16, ... .  */
+
+rtx
+generate_crc_table (unsigned HOST_WIDE_INT polynom, unsigned short crc_bits)
+{
+  gcc_assert (crc_bits <= 64);
+
+  /* Buf size - 24 letters + 6 '_'
+     + 20 numbers (2 for crc bit size + 2 for 0x + 16 for 64-bit polynomial)
+     + 1 for \0.  */
+  char buf[51];
+  sprintf (buf, "crc_table_for_crc_%u_polynomial_" HOST_WIDE_INT_PRINT_HEX,
+          crc_bits, polynom);
+
+  tree id = maybe_get_identifier (buf);
+  if (id)
+    return gen_rtx_SYMBOL_REF (Pmode, IDENTIFIER_POINTER (id));
+
+  id = get_identifier (buf);
+  return assemble_crc_table (id, polynom, crc_bits);
+}
+
+/* Generate table-based CRC code for the given CRC, INPUT_DATA and the
+   POLYNOMIAL (without leading 1).
+
+   First, using POLYNOMIAL's value generates CRC table of 256 elements,
+   then generates the assembly for the following code,
+   where crc_bit_size and data_bit_size may be 8, 16, 32, 64, depending on CRC:
+
+     for (int i = 0; i < data_bit_size / 8; i++)
+       crc = (crc << 8) ^ crc_table[(crc >> (crc_bit_size - 8))
+                                   ^ (data >> (data_bit_size - (i + 1) * 8)
+                                   & 0xFF))];
+
+   So to take values from the table, we need 8-bit data.
+   If input data size is not 8, then first we extract upper 8 bits,
+   then the other 8 bits, and so on.  */
+
+void
+calculate_table_based_CRC (rtx *crc, const rtx &input_data,
+                          const rtx &polynomial,
+                          machine_mode crc_mode, machine_mode data_mode)
+{
+  unsigned short crc_bit_size = GET_MODE_BITSIZE (crc_mode).to_constant ();
+  unsigned short data_size = GET_MODE_SIZE (data_mode).to_constant ();
+  machine_mode mode = GET_MODE (*crc);
+  rtx tab = generate_crc_table (UINTVAL (polynomial), crc_bit_size);
+
+  for (unsigned short i = 0; i < data_size; i++)
+    {
+      /* crc >> (crc_bit_size - 8).  */
+      *crc = force_reg (crc_mode, *crc);
+      rtx op1 = expand_shift (RSHIFT_EXPR, mode, *crc, crc_bit_size - 8,
+                             NULL_RTX, 1);
+
+      /* data >> (8 * (GET_MODE_SIZE (data_mode).to_constant () - i - 1)).  */
+      unsigned range_8 = 8 * (data_size - i - 1);
+      rtx data = force_reg (data_mode, input_data);
+      data = expand_shift (RSHIFT_EXPR, mode, data, range_8, NULL_RTX, 1);
+
+      /* data >> (8 * (GET_MODE_SIZE (data_mode)
+                                       .to_constant () - i - 1)) & 0xFF.  */
+      rtx data_final = expand_and (mode, data,
+                                  gen_int_mode (255, data_mode), NULL_RTX);
+
+      /* (crc >> (crc_bit_size - 8)) ^ data_8bit.  */
+      rtx in = expand_binop (mode, xor_optab, op1, data_final,
+                            NULL_RTX, 1, OPTAB_WIDEN);
+
+      /* ((crc >> (crc_bit_size - 8)) ^ data_8bit) & 0xFF.  */
+      rtx index = expand_and (mode, in, gen_int_mode (255, mode),
+                             NULL_RTX);
+      int log_crc_size = exact_log2 (GET_MODE_SIZE (crc_mode).to_constant ());
+      index = expand_shift (LSHIFT_EXPR, mode, index,
+                           log_crc_size, NULL_RTX, 0);
+
+      rtx addr = gen_reg_rtx (Pmode);
+      convert_move (addr, index, 1);
+      addr = expand_binop (Pmode, add_optab, addr, tab, NULL_RTX,
+                           0, OPTAB_DIRECT);
+
+      /* crc_table[(crc >> (crc_bit_size - 8)) ^ data_8bit]  */
+      rtx tab_el = validize_mem (gen_rtx_MEM (crc_mode, addr));
+
+      /* (crc << 8) if CRC is larger than 8, otherwise crc = 0.  */
+      rtx high = NULL_RTX;
+      if (crc_bit_size != 8)
+       high = expand_shift (LSHIFT_EXPR, mode, *crc, 8, NULL_RTX, 0);
+      else
+       high = gen_int_mode (0, mode);
+
+      /* crc = (crc << 8)
+              ^ crc_table[(crc >> (crc_bit_size - 8)) ^ data_8bit];  */
+      *crc = expand_binop (mode, xor_optab, tab_el, high, NULL_RTX, 1,
+                          OPTAB_WIDEN);
+    }
+}
+
+/* Generate table-based CRC code for the given CRC, INPUT_DATA and the
+   POLYNOMIAL (without leading 1).
+
+   CRC is OP1, data is OP2 and the polynomial is OP3.
+   This must generate a CRC table and an assembly for the following code,
+   where crc_bit_size and data_bit_size may be 8, 16, 32, 64:
+   uint_crc_bit_size_t
+   crc_crc_bit_size (uint_crc_bit_size_t crc_init,
+                    uint_data_bit_size_t data, size_t size)
+   {
+     uint_crc_bit_size_t crc = crc_init;
+     for (int i = 0; i < data_bit_size / 8; i++)
+       crc = (crc << 8) ^ crc_table[(crc >> (crc_bit_size - 8))
+                                   ^ (data >> (data_bit_size - (i + 1) * 8)
+                                   & 0xFF))];
+     return crc;
+   }  */
+
+void
+expand_crc_table_based (rtx op0, rtx op1, rtx op2, rtx op3,
+                       machine_mode data_mode)
+{
+  gcc_assert (!CONST_INT_P (op0));
+  gcc_assert (CONST_INT_P (op3));
+  machine_mode crc_mode = GET_MODE (op0);
+  rtx crc = gen_reg_rtx (crc_mode);
+  convert_move (crc, op1, 0);
+  calculate_table_based_CRC (&crc, op2, op3, crc_mode, data_mode);
+  convert_move (op0, crc, 0);
+}
+
+/* Generate the common operation for reflecting values:
+   *OP = (*OP & AND1_VALUE) << SHIFT_VAL | (*OP & AND2_VALUE) >> SHIFT_VAL;  */
+
+void
+gen_common_operation_to_reflect (rtx *op,
+                                unsigned HOST_WIDE_INT and1_value,
+                                unsigned HOST_WIDE_INT and2_value,
+                                unsigned shift_val)
+{
+  rtx op1 = expand_and (GET_MODE (*op), *op,
+                       gen_int_mode (and1_value, GET_MODE (*op)), NULL_RTX);
+  op1 = expand_shift (LSHIFT_EXPR, GET_MODE (*op), op1, shift_val, op1, 0);
+  rtx op2 = expand_and (GET_MODE (*op), *op,
+                       gen_int_mode (and2_value, GET_MODE (*op)), NULL_RTX);
+  op2 = expand_shift (RSHIFT_EXPR, GET_MODE (*op), op2, shift_val, op2, 1);
+  *op = expand_binop (GET_MODE (*op), ior_optab, op1,
+                     op2, *op, 0, OPTAB_LIB_WIDEN);
+}
+
+/* Reflect 64-bit value for the 64-bit target.  */
+
+void
+reflect_64_bit_value (rtx *op)
+{
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x00000000FFFFFFFF),
+                                  HOST_WIDE_INT_C (0xFFFFFFFF00000000), 32);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x0000FFFF0000FFFF),
+                                  HOST_WIDE_INT_C (0xFFFF0000FFFF0000), 16);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x00FF00FF00FF00FF),
+                                  HOST_WIDE_INT_C (0xFF00FF00FF00FF00), 8);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x0F0F0F0F0F0F0F0F),
+                                  HOST_WIDE_INT_C (0xF0F0F0F0F0F0F0F0), 4);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x3333333333333333),
+                                  HOST_WIDE_INT_C (0xCCCCCCCCCCCCCCCC), 2);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x5555555555555555),
+                                  HOST_WIDE_INT_C (0xAAAAAAAAAAAAAAAA), 1);
+}
+
+/* Reflect 32-bit value for the 32-bit target.  */
+
+void
+reflect_32_bit_value (rtx *op)
+{
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x0000FFFF),
+                                 HOST_WIDE_INT_C (0xFFFF0000), 16);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x00FF00FF),
+                                 HOST_WIDE_INT_C (0xFF00FF00), 8);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x0F0F0F0F),
+                                  HOST_WIDE_INT_C (0xF0F0F0F0), 4);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x33333333),
+                                  HOST_WIDE_INT_C (0xCCCCCCCC), 2);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x55555555),
+                                  HOST_WIDE_INT_C (0xAAAAAAAA), 1);
+}
+
+/* Reflect 16-bit value for the 16-bit target.  */
+
+void
+reflect_16_bit_value (rtx *op)
+{
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x00FF),
+                                  HOST_WIDE_INT_C (0xFF00), 8);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x0F0F),
+                                  HOST_WIDE_INT_C (0xF0F0), 4);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x3333),
+                                  HOST_WIDE_INT_C (0xCCCC), 2);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x5555),
+                                  HOST_WIDE_INT_C (0xAAAA), 1);
+}
+
+/* Reflect 8-bit value for the 8-bit target.  */
+
+void
+reflect_8_bit_value (rtx *op)
+{
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x0F),
+                                  HOST_WIDE_INT_C (0xF0), 4);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x33),
+                                  HOST_WIDE_INT_C (0xCC), 2);
+  gen_common_operation_to_reflect (op, HOST_WIDE_INT_C (0x55),
+                                  HOST_WIDE_INT_C (0xAA), 1);
+}
+
+/* Generate instruction sequence which reflects the value of the OP
+   using shift, and, or operations.  OP's mode may be less than word_mode.  */
+
+void
+generate_reflecting_code_standard (rtx *op)
+{
+  gcc_assert (GET_MODE_BITSIZE (GET_MODE (*op)).to_constant ()  >= 8
+             && GET_MODE_BITSIZE (GET_MODE (*op)).to_constant () <= 64);
+
+  if (GET_MODE_BITSIZE (GET_MODE (*op)).to_constant () == 64)
+    reflect_64_bit_value (op);
+  else if (GET_MODE_BITSIZE (GET_MODE (*op)).to_constant () == 32)
+    reflect_32_bit_value (op);
+  else if (GET_MODE_BITSIZE (GET_MODE (*op)).to_constant () == 16)
+    reflect_16_bit_value (op);
+  else
+    reflect_8_bit_value (op);
+}
+
+/* Generate table-based reversed CRC code for the given CRC, INPUT_DATA and
+   the POLYNOMIAL (without leading 1).
+
+   CRC is OP1, data is OP2 and the polynomial is OP3.
+   This must generate CRC table and assembly for the following code,
+   where crc_bit_size and data_bit_size may be 8, 16, 32, 64:
+   uint_crc_bit_size_t
+   crc_crc_bit_size (uint_crc_bit_size_t crc_init,
+                          uint_data_bit_size_t data, size_t size)
+   {
+     reflect (crc_init)
+     uint_crc_bit_size_t crc = crc_init;
+     reflect (data);
+     for (int i = 0; i < data_bit_size / 8; i++)
+       crc = (crc << 8) ^ crc_table[(crc >> (crc_bit_size - 8))
+                         ^ (data >> (data_bit_size - (i + 1) * 8) & 0xFF))];
+     reflect (crc);
+     return crc;
+   }  */
+
+void
+expand_reversed_crc_table_based (rtx op0, rtx op1, rtx op2, rtx op3,
+                                machine_mode data_mode,
+                                void (*gen_reflecting_code) (rtx *op))
+{
+  gcc_assert (!CONST_INT_P (op0));
+  gcc_assert (CONST_INT_P (op3));
+  machine_mode crc_mode = GET_MODE (op0);
+
+  rtx crc = gen_reg_rtx (crc_mode);
+  convert_move (crc, op1, 0);
+  gen_reflecting_code (&crc);
+
+  rtx data = gen_reg_rtx (data_mode);
+  convert_move (data, op2, 0);
+  gen_reflecting_code (&data);
+
+  calculate_table_based_CRC (&crc, data, op3, crc_mode, data_mode);
+
+  gen_reflecting_code (&crc);
+  convert_move (op0, crc, 0);
+}
diff --git a/gcc/expr.h b/gcc/expr.h
index 04782b15f192..5dd059de801b 100644
--- a/gcc/expr.h
+++ b/gcc/expr.h
@@ -377,4 +377,10 @@ extern rtx expr_size (tree);
 extern bool mem_ref_refers_to_non_mem_p (tree);
 extern bool non_mem_decl_p (tree);
 
+/* Generate table-based CRC.  */
+extern void generate_reflecting_code_standard (rtx *);
+extern void expand_crc_table_based (rtx, rtx, rtx, rtx, machine_mode);
+extern void expand_reversed_crc_table_based (rtx, rtx, rtx, rtx, machine_mode,
+                                            void (*) (rtx *));
+
 #endif /* GCC_EXPR_H */
diff --git a/gcc/internal-fn.cc b/gcc/internal-fn.cc
index a45b32918000..c7c3f1c34bae 100644
--- a/gcc/internal-fn.cc
+++ b/gcc/internal-fn.cc
@@ -191,6 +191,7 @@ init_internal_fns ()
 #define mask_fold_left_direct { 1, 1, false }
 #define mask_len_fold_left_direct { 1, 1, false }
 #define check_ptrs_direct { 0, 0, false }
+#define crc_direct { 1, -1, true }
 
 const direct_internal_fn_info direct_internal_fn_array[IFN_LAST + 1] = {
 #define DEF_INTERNAL_FN(CODE, FLAGS, FNSPEC) not_direct,
@@ -4054,6 +4055,79 @@ expand_convert_optab_fn (internal_fn fn, gcall *stmt, 
convert_optab optab,
   expand_fn_using_insn (stmt, icode, 1, nargs);
 }
 
+/* Expand CRC call STMT.  */
+
+static void
+expand_crc_optab_fn (internal_fn fn, gcall *stmt, convert_optab optab)
+{
+  tree lhs = gimple_call_lhs (stmt);
+  tree rhs1 = gimple_call_arg (stmt, 0); // crc
+  tree rhs2 = gimple_call_arg (stmt, 1); // data
+  tree rhs3 = gimple_call_arg (stmt, 2); // polynomial
+
+  tree result_type = TREE_TYPE (lhs);
+  tree data_type = TREE_TYPE (rhs2);
+
+  gcc_assert (TYPE_MODE (result_type) >= TYPE_MODE (data_type));
+
+  rtx dest = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
+  rtx crc = expand_normal (rhs1);
+  rtx data = expand_normal (rhs2);
+  gcc_assert (TREE_CODE (rhs3) == INTEGER_CST);
+  rtx polynomial = gen_rtx_CONST_INT (TYPE_MODE (result_type),
+  TREE_INT_CST_LOW (rhs3));
+
+  /* Use target specific expansion if it exists.
+     Otherwise, generate table-based CRC.  */
+  if (direct_internal_fn_supported_p (fn, tree_pair (data_type, result_type),
+                                     OPTIMIZE_FOR_SPEED))
+    {
+      class expand_operand ops[4];
+      create_call_lhs_operand (&ops[0], dest, TYPE_MODE (result_type));
+      create_input_operand (&ops[1], crc, TYPE_MODE (result_type));
+      create_input_operand (&ops[2], data, TYPE_MODE (data_type));
+      create_input_operand (&ops[3], polynomial, TYPE_MODE (result_type));
+      insn_code icode = convert_optab_handler (optab, TYPE_MODE (data_type),
+                                              TYPE_MODE (result_type));
+      expand_insn (icode, 4, ops);
+      assign_call_lhs (lhs, dest, &ops[0]);
+    }
+  else
+    {
+      /* We're bypassing all the operand conversions that are done in the
+        case when we get an icode, operands and pass that off to expand_insn.
+
+        That path has special case handling for promoted return values which
+        we must emulate here (is the same kind of special treatment ever
+        needed for input arguments here?).
+
+        In particular we do not want to store directly into a promoted
+        SUBREG destination, instead store into a suitably sized pseudo.  */
+      rtx orig_dest = dest;
+      if (SUBREG_P (dest) && SUBREG_PROMOTED_VAR_P (dest))
+       dest = gen_reg_rtx (GET_MODE (dest));
+
+      /* If it's IFN_CRC generate bit-forward CRC.  */
+      if (fn == IFN_CRC)
+       expand_crc_table_based (dest, crc, data, polynomial,
+                               TYPE_MODE (data_type));
+      else
+       /* If it's IFN_CRC_REV generate bit-reversed CRC.  */
+       expand_reversed_crc_table_based (dest, crc, data, polynomial,
+                                        TYPE_MODE (data_type),
+                                        generate_reflecting_code_standard);
+
+      /* Now get the return value where it needs to be, taking care to
+        ensure it's promoted appropriately if the ABI demands it.
+
+        Re-use assign_call_lhs to handle the details.  */
+      class expand_operand ops[4];
+      create_call_lhs_operand (&ops[0], dest, TYPE_MODE (result_type));
+      ops[0].value = dest;
+      assign_call_lhs (lhs, orig_dest, &ops[0]);
+    }
+}
+
 /* Expanders for optabs that can use expand_direct_optab_fn.  */
 
 #define expand_unary_optab_fn(FN, STMT, OPTAB) \
@@ -4190,6 +4264,7 @@ multi_vector_optab_supported_p (convert_optab optab, 
tree_pair types,
 #define direct_cond_len_unary_optab_supported_p direct_optab_supported_p
 #define direct_cond_len_binary_optab_supported_p direct_optab_supported_p
 #define direct_cond_len_ternary_optab_supported_p direct_optab_supported_p
+#define direct_crc_optab_supported_p convert_optab_supported_p
 #define direct_mask_load_optab_supported_p convert_optab_supported_p
 #define direct_load_lanes_optab_supported_p multi_vector_optab_supported_p
 #define direct_mask_load_lanes_optab_supported_p multi_vector_optab_supported_p
diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def
index e993c99c558c..6e84c693697b 100644
--- a/gcc/internal-fn.def
+++ b/gcc/internal-fn.def
@@ -202,6 +202,8 @@ along with GCC; see the file COPYING3.  If not see
                                cond_len_##UNSIGNED_OPTAB, cond_len_##TYPE)
 #endif
 
+DEF_INTERNAL_OPTAB_FN (CRC, ECF_CONST | ECF_NOTHROW, crc, crc)
+DEF_INTERNAL_OPTAB_FN (CRC_REV, ECF_CONST | ECF_NOTHROW, crc_rev, crc)
 DEF_INTERNAL_OPTAB_FN (MASK_LOAD, ECF_PURE, maskload, mask_load)
 DEF_INTERNAL_OPTAB_FN (LOAD_LANES, ECF_CONST, vec_load_lanes, load_lanes)
 DEF_INTERNAL_OPTAB_FN (MASK_LOAD_LANES, ECF_PURE,
diff --git a/gcc/optabs.def b/gcc/optabs.def
index 75f39d85adab..5d75b1379acf 100644
--- a/gcc/optabs.def
+++ b/gcc/optabs.def
@@ -85,6 +85,8 @@ OPTAB_CD(smsub_widen_optab, "msub$b$a4")
 OPTAB_CD(umsub_widen_optab, "umsub$b$a4")
 OPTAB_CD(ssmsub_widen_optab, "ssmsub$b$a4")
 OPTAB_CD(usmsub_widen_optab, "usmsub$a$b4")
+OPTAB_CD(crc_optab, "crc$a$b4")
+OPTAB_CD(crc_rev_optab, "crc_rev$a$b4")
 OPTAB_CD(vec_load_lanes_optab, "vec_load_lanes$a$b")
 OPTAB_CD(vec_store_lanes_optab, "vec_store_lanes$a$b")
 OPTAB_CD(vec_mask_load_lanes_optab, "vec_mask_load_lanes$a$b")

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