target/riscv: Enable PC-relative translation

Add a base pc_save for PC-relative translation(CF_PCREL).
Diable the directly sync pc from tb by riscv_cpu_synchronize_from_tb.
Use gen_pc_plus_diff to get the pc-relative address.
Enable CF_PCREL in System mode.

Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20230526072124.298466-7-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -721,16 +721,18 @@ static vaddr riscv_cpu_get_pc(CPUState *cs)
 static void riscv_cpu_synchronize_from_tb(CPUState *cs,
                                           const TranslationBlock *tb)
 {
-    RISCVCPU *cpu = RISCV_CPU(cs);
+    if (!(tb_cflags(tb) & CF_PCREL)) {
-    CPURISCVState *env = &cpu->env;
+        RISCVCPU *cpu = RISCV_CPU(cs);
-    RISCVMXL xl = FIELD_EX32(tb->flags, TB_FLAGS, XL);
+        CPURISCVState *env = &cpu->env;
+        RISCVMXL xl = FIELD_EX32(tb->flags, TB_FLAGS, XL);
 
-    tcg_debug_assert(!(cs->tcg_cflags & CF_PCREL));
+        tcg_debug_assert(!(cs->tcg_cflags & CF_PCREL));
 
-    if (xl == MXL_RV32) {
+        if (xl == MXL_RV32) {
-        env->pc = (int32_t) tb->pc;
+            env->pc = (int32_t) tb->pc;
-    } else {
+        } else {
-        env->pc = tb->pc;
+            env->pc = tb->pc;
+        }
     }
 }
 
@@ -756,11 +758,18 @@ static void riscv_restore_state_to_opc(CPUState *cs,
     RISCVCPU *cpu = RISCV_CPU(cs);
     CPURISCVState *env = &cpu->env;
     RISCVMXL xl = FIELD_EX32(tb->flags, TB_FLAGS, XL);
+    target_ulong pc;
+
+    if (tb_cflags(tb) & CF_PCREL) {
+        pc = (env->pc & TARGET_PAGE_MASK) | data[0];
+    } else {
+        pc = data[0];
+    }
 
     if (xl == MXL_RV32) {
-        env->pc = (int32_t)data[0];
+        env->pc = (int32_t)pc;
     } else {
-        env->pc = data[0];
+        env->pc = pc;
     }
     env->bins = data[1];
 }
@@ -1343,6 +1352,8 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
     }
 
 #ifndef CONFIG_USER_ONLY
+    cs->tcg_cflags |= CF_PCREL;
+
     if (cpu->cfg.ext_sstc) {
         riscv_timer_init(cpu);
     }

target/riscv/insn_trans/trans_rvi.c.inc

@@ -38,7 +38,9 @@ static bool trans_lui(DisasContext *ctx, arg_lui *a)
 
 static bool trans_auipc(DisasContext *ctx, arg_auipc *a)
 {
-    gen_set_gpri(ctx, a->rd, a->imm + ctx->base.pc_next);
+    TCGv target_pc = dest_gpr(ctx, a->rd);
+    gen_pc_plus_diff(target_pc, ctx, a->imm);
+    gen_set_gpr(ctx, a->rd, target_pc);
     return true;
 }
 
@@ -52,6 +54,7 @@ static bool trans_jalr(DisasContext *ctx, arg_jalr *a)
 {
     TCGLabel *misaligned = NULL;
     TCGv target_pc = tcg_temp_new();
+    TCGv succ_pc = dest_gpr(ctx, a->rd);
 
     tcg_gen_addi_tl(target_pc, get_gpr(ctx, a->rs1, EXT_NONE), a->imm);
     tcg_gen_andi_tl(target_pc, target_pc, (target_ulong)-2);
@@ -68,7 +71,9 @@ static bool trans_jalr(DisasContext *ctx, arg_jalr *a)
         tcg_gen_brcondi_tl(TCG_COND_NE, t0, 0x0, misaligned);
     }
 
-    gen_set_gpri(ctx, a->rd, ctx->pc_succ_insn);
+    gen_pc_plus_diff(succ_pc, ctx, ctx->cur_insn_len);
+    gen_set_gpr(ctx, a->rd, succ_pc);
+
     tcg_gen_mov_tl(cpu_pc, target_pc);
     lookup_and_goto_ptr(ctx);
 
@@ -158,6 +163,7 @@ static bool gen_branch(DisasContext *ctx, arg_b *a, TCGCond cond)
     TCGLabel *l = gen_new_label();
     TCGv src1 = get_gpr(ctx, a->rs1, EXT_SIGN);
     TCGv src2 = get_gpr(ctx, a->rs2, EXT_SIGN);
+    target_ulong orig_pc_save = ctx->pc_save;
 
     if (get_xl(ctx) == MXL_RV128) {
         TCGv src1h = get_gprh(ctx, a->rs1);
@@ -171,6 +177,7 @@ static bool gen_branch(DisasContext *ctx, arg_b *a, TCGCond cond)
         tcg_gen_brcond_tl(cond, src1, src2, l);
     }
     gen_goto_tb(ctx, 1, ctx->cur_insn_len);
+    ctx->pc_save = orig_pc_save;
 
     gen_set_label(l); /* branch taken */
 
@@ -183,6 +190,7 @@ static bool gen_branch(DisasContext *ctx, arg_b *a, TCGCond cond)
     } else {
         gen_goto_tb(ctx, 0, a->imm);
     }
+    ctx->pc_save = -1;
     ctx->base.is_jmp = DISAS_NORETURN;
 
     return true;

target/riscv/insn_trans/trans_rvzce.c.inc

@@ -302,7 +302,9 @@ static bool trans_cm_jalt(DisasContext *ctx, arg_cm_jalt *a)
 
     /* c.jt vs c.jalt depends on the index. */
     if (a->index >= 32) {
-        gen_set_gpri(ctx, xRA, ctx->pc_succ_insn);
+        TCGv succ_pc = dest_gpr(ctx, xRA);
+        gen_pc_plus_diff(succ_pc, ctx, ctx->cur_insn_len);
+        gen_set_gpr(ctx, xRA, succ_pc);
     }
 
     tcg_gen_lookup_and_goto_ptr();

target/riscv/translate.c

@@ -62,6 +62,7 @@ typedef struct DisasContext {
     /* pc_succ_insn points to the instruction following base.pc_next */
     target_ulong pc_succ_insn;
     target_ulong cur_insn_len;
+    target_ulong pc_save;
     target_ulong priv_ver;
     RISCVMXL misa_mxl_max;
     RISCVMXL xl;
@@ -230,15 +231,24 @@ static void gen_pc_plus_diff(TCGv target, DisasContext *ctx,
 {
     target_ulong dest = ctx->base.pc_next + diff;
 
-    if (get_xl(ctx) == MXL_RV32) {
+    assert(ctx->pc_save != -1);
-        dest = (int32_t)dest;
+    if (tb_cflags(ctx->base.tb) & CF_PCREL) {
+        tcg_gen_addi_tl(target, cpu_pc, dest - ctx->pc_save);
+        if (get_xl(ctx) == MXL_RV32) {
+            tcg_gen_ext32s_tl(target, target);
+        }
+    } else {
+        if (get_xl(ctx) == MXL_RV32) {
+            dest = (int32_t)dest;
+        }
+        tcg_gen_movi_tl(target, dest);
     }
-    tcg_gen_movi_tl(target, dest);
 }
 
 static void gen_update_pc(DisasContext *ctx, target_long diff)
 {
     gen_pc_plus_diff(cpu_pc, ctx, diff);
+    ctx->pc_save = ctx->base.pc_next + diff;
 }
 
 static void generate_exception(DisasContext *ctx, int excp)
@@ -294,8 +304,21 @@ static void gen_goto_tb(DisasContext *ctx, int n, target_long diff)
       * direct block chain benefits will be small.
       */
     if (translator_use_goto_tb(&ctx->base, dest) && !ctx->itrigger) {
-        tcg_gen_goto_tb(n);
+        /*
-        gen_update_pc(ctx, diff);
+         * For pcrel, the pc must always be up-to-date on entry to
+         * the linked TB, so that it can use simple additions for all
+         * further adjustments.  For !pcrel, the linked TB is compiled
+         * to know its full virtual address, so we can delay the
+         * update to pc to the unlinked path.  A long chain of links
+         * can thus avoid many updates to the PC.
+         */
+        if (tb_cflags(ctx->base.tb) & CF_PCREL) {
+            gen_update_pc(ctx, diff);
+            tcg_gen_goto_tb(n);
+        } else {
+            tcg_gen_goto_tb(n);
+            gen_update_pc(ctx, diff);
+        }
         tcg_gen_exit_tb(ctx->base.tb, n);
     } else {
         gen_update_pc(ctx, diff);
@@ -549,6 +572,8 @@ static void gen_set_fpr_d(DisasContext *ctx, int reg_num, TCGv_i64 t)
 
 static void gen_jal(DisasContext *ctx, int rd, target_ulong imm)
 {
+    TCGv succ_pc = dest_gpr(ctx, rd);
+
     /* check misaligned: */
     if (!has_ext(ctx, RVC) && !ctx->cfg_ptr->ext_zca) {
         if ((imm & 0x3) != 0) {
@@ -559,7 +584,9 @@ static void gen_jal(DisasContext *ctx, int rd, target_ulong imm)
         }
     }
 
-    gen_set_gpri(ctx, rd, ctx->pc_succ_insn);
+    gen_pc_plus_diff(succ_pc, ctx, ctx->cur_insn_len);
+    gen_set_gpr(ctx, rd, succ_pc);
+
     gen_goto_tb(ctx, 0, imm); /* must use this for safety */
     ctx->base.is_jmp = DISAS_NORETURN;
 }
@@ -1157,6 +1184,7 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
     RISCVCPU *cpu = RISCV_CPU(cs);
     uint32_t tb_flags = ctx->base.tb->flags;
 
+    ctx->pc_save = ctx->base.pc_first;
     ctx->pc_succ_insn = ctx->base.pc_first;
     ctx->priv = FIELD_EX32(tb_flags, TB_FLAGS, PRIV);
     ctx->mem_idx = FIELD_EX32(tb_flags, TB_FLAGS, MEM_IDX);
@@ -1192,8 +1220,13 @@ static void riscv_tr_tb_start(DisasContextBase *db, CPUState *cpu)
 static void riscv_tr_insn_start(DisasContextBase *dcbase, CPUState *cpu)
 {
     DisasContext *ctx = container_of(dcbase, DisasContext, base);
+    target_ulong pc_next = ctx->base.pc_next;
 
-    tcg_gen_insn_start(ctx->base.pc_next, 0);
+    if (tb_cflags(dcbase->tb) & CF_PCREL) {
+        pc_next &= ~TARGET_PAGE_MASK;
+    }
+
+    tcg_gen_insn_start(pc_next, 0);
     ctx->insn_start = tcg_last_op();
 }