target/riscv: Activate decodetree and implemnt LUI & AUIPC

for now only LUI & AUIPC are decoded and translated. If decodetree fails, we
fall back to the old decoder.

Backports commit 2a53cff418335ccb4719e9a94fde55f6ebcc895d from qemu

qemu/header_gen.py

@@ -5411,6 +5411,7 @@ riscv_symbols = (
     'cpu_riscv_set_fflags',
     'csr_read_helper',
     'csr_write_helper',
+    'decode_insn32',
     'do_raise_exception_err',
     'gen_helper_tlb_flush',
     'helper_csrrc',

qemu/riscv32.h

@@ -3332,6 +3332,7 @@
 #define cpu_riscv_set_fflags cpu_riscv_set_fflags_riscv32
 #define csr_read_helper csr_read_helper_riscv32
 #define csr_write_helper csr_write_helper_riscv32
+#define decode_insn32 decode_insn32_riscv32
 #define do_raise_exception_err do_raise_exception_err_riscv32
 #define gen_helper_tlb_flush gen_helper_tlb_flush_riscv32
 #define helper_csrrc helper_csrrc_riscv32

qemu/riscv64.h

@@ -3332,6 +3332,7 @@
 #define cpu_riscv_set_fflags cpu_riscv_set_fflags_riscv64
 #define csr_read_helper csr_read_helper_riscv64
 #define csr_write_helper csr_write_helper_riscv64
+#define decode_insn32 decode_insn32_riscv64
 #define do_raise_exception_err do_raise_exception_err_riscv64
 #define gen_helper_tlb_flush gen_helper_tlb_flush_riscv64
 #define helper_csrrc helper_csrrc_riscv64

qemu/target/riscv/Makefile.objs

@@ -1,2 +1,12 @@
 obj-y += translate.o op_helper.o cpu_helper.o cpu.o csr.o fpu_helper.o pmp.o
 obj-y += unicorn.o
+
+DECODETREE = $(SRC_PATH)/scripts/decodetree.py
+
+target/riscv/decode_insn32.inc.c: \
+  $(SRC_PATH)/target/riscv/insn32.decode $(DECODETREE)
+	$(call quiet-command, \
+	  $(PYTHON) $(DECODETREE) -o $@ --decode decode_insn32 $<, \
+	  "GEN", $(TARGET_DIR)$@)
+
+target/riscv/translate.o: target/riscv/decode_insn32.inc.c

qemu/target/riscv/insn32.decode

@@ -0,0 +1,30 @@
+#
+# RISC-V translation routines for the RVXI Base Integer Instruction Set.
+#
+# Copyright (c) 2018 Peer Adelt, peer.adelt@hni.uni-paderborn.de
+#                    Bastian Koppelmann, kbastian@mail.uni-paderborn.de
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms and conditions of the GNU General Public License,
+# version 2 or later, as published by the Free Software Foundation.
+#
+# This program is distributed in the hope 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
+# this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Fields:
+%rd        7:5
+
+# immediates:
+%imm_u    12:s20                 !function=ex_shift_12
+
+# Formats 32:
+@u       ....................      ..... .......         imm=%imm_u          %rd
+
+# *** RV32I Base Instruction Set ***
+lui      ....................       ..... 0110111 @u
+auipc    ....................       ..... 0010111 @u

qemu/target/riscv/insn_trans/trans_rvi.inc.c

@@ -0,0 +1,37 @@
+/*
+ * RISC-V translation routines for the RVXI Base Integer Instruction Set.
+ *
+ * Copyright (c) 2016-2017 Sagar Karandikar, sagark@eecs.berkeley.edu
+ * Copyright (c) 2018 Peer Adelt, peer.adelt@hni.uni-paderborn.de
+ *                    Bastian Koppelmann, kbastian@mail.uni-paderborn.de
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+static bool trans_lui(DisasContext *ctx, arg_lui *a)
+{
+    if (a->rd != 0) {
+        TCGContext *tcg_ctx = ctx->uc->tcg_ctx;
+        tcg_gen_movi_tl(tcg_ctx, tcg_ctx->cpu_gpr[a->rd], a->imm);
+    }
+    return true;
+}
+
+static bool trans_auipc(DisasContext *ctx, arg_auipc *a)
+{
+    if (a->rd != 0) {
+        TCGContext *tcg_ctx = ctx->uc->tcg_ctx;
+        tcg_gen_movi_tl(tcg_ctx, tcg_ctx->cpu_gpr[a->rd], a->imm + ctx->base.pc_next);
+    }
+    return true;
+}

qemu/target/riscv/translate.c

@@ -1946,6 +1946,19 @@ static void decode_RV32_64C(DisasContext *ctx)
     }
 }
 
+#define EX_SH(amount) \
+    static int ex_shift_##amount(int imm) \
+    {                                         \
+        return imm << amount;                 \
+    }
+EX_SH(12)
+
+bool decode_insn32(DisasContext *ctx, uint32_t insn);
+/* Include the auto-generated decoder for 32 bit insn */
+#include "decode_insn32.inc.c"
+/* Include insn module translation function */
+#include "insn_trans/trans_rvi.inc.c"
+
 static void decode_RV32_64G(DisasContext *ctx)
 {
     TCGContext *tcg_ctx = ctx->uc->tcg_ctx;
@@ -1967,19 +1980,6 @@ static void decode_RV32_64G(DisasContext *ctx)
     imm = GET_IMM(ctx->opcode);
 
     switch (op) {
-    case OPC_RISC_LUI:
-        if (rd == 0) {
-            break; /* NOP */
-        }
-        tcg_gen_movi_tl(tcg_ctx, tcg_ctx->cpu_gpr_risc[rd], sextract64(ctx->opcode, 12, 20) << 12);
-        break;
-    case OPC_RISC_AUIPC:
-        if (rd == 0) {
-            break; /* NOP */
-        }
-        tcg_gen_movi_tl(tcg_ctx, tcg_ctx->cpu_gpr_risc[rd], (sextract64(ctx->opcode, 12, 20) << 12) +
-               ctx->base.pc_next);
-        break;
     case OPC_RISC_JAL:
         imm = GET_JAL_IMM(ctx->opcode);
         gen_jal(ctx, rd, imm);
@@ -2084,7 +2084,10 @@ static void decode_opc(DisasContext *ctx)
         }
     } else {
         ctx->pc_succ_insn = ctx->base.pc_next + 4;
-        decode_RV32_64G(ctx);
+        if (!decode_insn32(ctx, ctx->opcode)) {
+            /* fallback to old decoder */
+            decode_RV32_64G(ctx);
+        }
     }
 }