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>

1 files changed, 40 insertions, 7 deletions

diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 7fb4cbe84c..bd2da9b079 100644
--- a/target/riscv/translate.c
+++ b/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) {
-        dest = (int32_t)dest;
+    assert(ctx->pc_save != -1);
+    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;
+
+    if (tb_cflags(dcbase->tb) & CF_PCREL) {
+        pc_next &= ~TARGET_PAGE_MASK;
+    }
 
-    tcg_gen_insn_start(ctx->base.pc_next, 0);
+    tcg_gen_insn_start(pc_next, 0);
     ctx->insn_start = tcg_last_op();
 }