;; Machine description for RISC-V atomic operations. ;; Copyright (C) 2011-2021 Free Software Foundation, Inc. ;; Contributed by Andrew Waterman (andrew@sifive.com). ;; Based on MIPS target for GNU compiler.

;; This file is part of GCC.

;; GCC is free software; you can redistribute it and/or modify ;; it under the terms of the GNU General Public License as published by ;; the Free Software Foundation; either version 3, or (at your option) ;; any later version.

;; GCC is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License ;; along with GCC; see the file COPYING3. If not see ;; http://www.gnu.org/licenses/.

(define_c_enum “unspec” [ UNSPEC_COMPARE_AND_SWAP UNSPEC_SYNC_OLD_OP UNSPEC_SYNC_EXCHANGE UNSPEC_ATOMIC_STORE UNSPEC_MEMORY_BARRIER ])

(define_code_iterator any_atomic [plus ior xor and]) (define_code_attr atomic_optab [(plus “add”) (ior “or”) (xor “xor”) (and “and”)])

;; Memory barriers.

(define_expand “mem_thread_fence” [(match_operand:SI 0 “const_int_operand” "")] ;; model "" { if (INTVAL (operands[0]) != MEMMODEL_RELAXED) { rtx mem = gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (Pmode)); MEM_VOLATILE_P (mem) = 1; emit_insn (gen_mem_thread_fence_1 (mem, operands[0])); } DONE; })

;; Until the RISC-V memory model (hence its mapping from C++) is finalized, ;; conservatively emit a full FENCE. (define_insn “mem_thread_fence_1” [(set (match_operand:BLK 0 "" "") (unspec:BLK [(match_dup 0)] UNSPEC_MEMORY_BARRIER)) (match_operand:SI 1 “const_int_operand” "")] ;; model "" “fence\tiorw,iorw”)

;; Atomic memory operations.

;; Implement atomic stores with amoswap. Fall back to fences for atomic loads. (define_insn “atomic_store” [(set (match_operand:GPR 0 “memory_operand” “=A”) (unspec_volatile:GPR [(match_operand:GPR 1 “reg_or_0_operand” “rJ”) (match_operand:SI 2 “const_int_operand”)] ;; model UNSPEC_ATOMIC_STORE))] “TARGET_ATOMIC” “%F2amoswap.%A2 zero,%z1,%0” [(set (attr “length”) (const_int 8))])

(define_insn “atomic_<atomic_optab>” [(set (match_operand:GPR 0 “memory_operand” “+A”) (unspec_volatile:GPR [(any_atomic:GPR (match_dup 0) (match_operand:GPR 1 “reg_or_0_operand” “rJ”)) (match_operand:SI 2 “const_int_operand”)] ;; model UNSPEC_SYNC_OLD_OP))] “TARGET_ATOMIC” “%F2amo.%A2 zero,%z1,%0” [(set (attr “length”) (const_int 8))])

(define_insn “atomic_fetch_<atomic_optab>” [(set (match_operand:GPR 0 “register_operand” “=&r”) (match_operand:GPR 1 “memory_operand” “+A”)) (set (match_dup 1) (unspec_volatile:GPR [(any_atomic:GPR (match_dup 1) (match_operand:GPR 2 “reg_or_0_operand” “rJ”)) (match_operand:SI 3 “const_int_operand”)] ;; model UNSPEC_SYNC_OLD_OP))] “TARGET_ATOMIC” “%F3amo.%A3 %0,%z2,%1” [(set (attr “length”) (const_int 8))])

(define_insn “atomic_exchange” [(set (match_operand:GPR 0 “register_operand” “=&r”) (unspec_volatile:GPR [(match_operand:GPR 1 “memory_operand” “+A”) (match_operand:SI 3 “const_int_operand”)] ;; model UNSPEC_SYNC_EXCHANGE)) (set (match_dup 1) (match_operand:GPR 2 “register_operand” “0”))] “TARGET_ATOMIC” “%F3amoswap.%A3 %0,%z2,%1” [(set (attr “length”) (const_int 8))])

(define_insn “atomic_cas_value_strong” [(set (match_operand:GPR 0 “register_operand” “=&r”) (match_operand:GPR 1 “memory_operand” “+A”)) (set (match_dup 1) (unspec_volatile:GPR [(match_operand:GPR 2 “reg_or_0_operand” “rJ”) (match_operand:GPR 3 “reg_or_0_operand” “rJ”) (match_operand:SI 4 “const_int_operand”) ;; mod_s (match_operand:SI 5 “const_int_operand”)] ;; mod_f UNSPEC_COMPARE_AND_SWAP)) (clobber (match_scratch:GPR 6 “=&r”))] “TARGET_ATOMIC” “%F5 1: lr.%A5 %0,%1; bne %0,%z2,1f; sc.%A4 %6,%z3,%1; bnez %6,1b; 1:” [(set (attr “length”) (const_int 20))])

(define_expand “atomic_compare_and_swap” [(match_operand:SI 0 “register_operand” "") ;; bool output (match_operand:GPR 1 “register_operand” "") ;; val output (match_operand:GPR 2 “memory_operand” "") ;; memory (match_operand:GPR 3 “reg_or_0_operand” "") ;; expected value (match_operand:GPR 4 “reg_or_0_operand” "") ;; desired value (match_operand:SI 5 “const_int_operand” "") ;; is_weak (match_operand:SI 6 “const_int_operand” "") ;; mod_s (match_operand:SI 7 “const_int_operand” "")] ;; mod_f “TARGET_ATOMIC” { emit_insn (gen_atomic_cas_value_strong (operands[1], operands[2], operands[3], operands[4], operands[6], operands[7]));

rtx compare = operands[1]; if (operands[3] != const0_rtx) { rtx difference = gen_rtx_MINUS (mode, operands[1], operands[3]); compare = gen_reg_rtx (mode); emit_insn (gen_rtx_SET (compare, difference)); }

if (word_mode != mode) { rtx reg = gen_reg_rtx (word_mode); emit_insn (gen_rtx_SET (reg, gen_rtx_SIGN_EXTEND (word_mode, compare))); compare = reg; }

emit_insn (gen_rtx_SET (operands[0], gen_rtx_EQ (SImode, compare, const0_rtx))); DONE; })

(define_expand “atomic_test_and_set” [(match_operand:QI 0 “register_operand” "") ;; bool output (match_operand:QI 1 “memory_operand” “+A”) ;; memory (match_operand:SI 2 “const_int_operand” "")] ;; model “TARGET_ATOMIC” { /* We have no QImode atomics, so use the address LSBs to form a mask, then use an aligned SImode atomic. */ rtx result = operands[0]; rtx mem = operands[1]; rtx model = operands[2]; rtx addr = force_reg (Pmode, XEXP (mem, 0));

rtx aligned_addr = gen_reg_rtx (Pmode); emit_move_insn (aligned_addr, gen_rtx_AND (Pmode, addr, GEN_INT (-4)));

rtx aligned_mem = change_address (mem, SImode, aligned_addr); set_mem_alias_set (aligned_mem, 0);

rtx offset = gen_reg_rtx (SImode); emit_move_insn (offset, gen_rtx_AND (SImode, gen_lowpart (SImode, addr), GEN_INT (3)));

rtx tmp = gen_reg_rtx (SImode); emit_move_insn (tmp, GEN_INT (1));

rtx shmt = gen_reg_rtx (SImode); emit_move_insn (shmt, gen_rtx_ASHIFT (SImode, offset, GEN_INT (3)));

rtx word = gen_reg_rtx (SImode); emit_move_insn (word, gen_rtx_ASHIFT (SImode, tmp, gen_lowpart (QImode, shmt)));

tmp = gen_reg_rtx (SImode); emit_insn (gen_atomic_fetch_orsi (tmp, aligned_mem, word, model));

emit_move_insn (gen_lowpart (SImode, result), gen_rtx_LSHIFTRT (SImode, tmp, gen_lowpart (QImode, shmt))); DONE; })