target/alpha: Implement CF_PCREL

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20240503072014.24751-10-philmd@linaro.org>

target/alpha/cpu.c

@@ -38,13 +38,28 @@ static vaddr alpha_cpu_get_pc(CPUState *cs)
     return env->pc;
 }
 
+static void alpha_cpu_synchronize_from_tb(CPUState *cs,
+                                          const TranslationBlock *tb)
+{
+    /* The program counter is always up to date with CF_PCREL. */
+    if (!(tb_cflags(tb) & CF_PCREL)) {
+        CPUAlphaState *env = cpu_env(cs);
+        env->pc = tb->pc;
+    }
+}
+
 static void alpha_restore_state_to_opc(CPUState *cs,
                                        const TranslationBlock *tb,
                                        const uint64_t *data)
 {
     CPUAlphaState *env = cpu_env(cs);
+
+    if (tb_cflags(tb) & CF_PCREL) {
+        env->pc = (env->pc & TARGET_PAGE_MASK) | data[0];
+    } else {
         env->pc = data[0];
     }
+}
 
 static bool alpha_cpu_has_work(CPUState *cs)
 {
@@ -78,6 +93,11 @@ static void alpha_cpu_realizefn(DeviceState *dev, Error **errp)
     AlphaCPUClass *acc = ALPHA_CPU_GET_CLASS(dev);
     Error *local_err = NULL;
 
+#ifndef CONFIG_USER_ONLY
+    /* Use pc-relative instructions in system-mode */
+    cs->tcg_cflags |= CF_PCREL;
+#endif
+
     cpu_exec_realizefn(cs, &local_err);
     if (local_err != NULL) {
         error_propagate(errp, local_err);
@@ -190,6 +210,7 @@ static const struct SysemuCPUOps alpha_sysemu_ops = {
 
 static const TCGCPUOps alpha_tcg_ops = {
     .initialize = alpha_translate_init,
+    .synchronize_from_tb = alpha_cpu_synchronize_from_tb,
     .restore_state_to_opc = alpha_restore_state_to_opc,
 
 #ifdef CONFIG_USER_ONLY

target/alpha/translate.c

@@ -54,6 +54,9 @@ struct DisasContext {
     uint32_t tbflags;
     int mem_idx;
 
+    /* True if generating pc-relative code.  */
+    bool pcrel;
+
     /* implver and amask values for this CPU.  */
     int implver;
     int amask;
@@ -254,7 +257,12 @@ static void st_flag_byte(TCGv val, unsigned shift)
 
 static void gen_pc_disp(DisasContext *ctx, TCGv dest, int32_t disp)
 {
-    tcg_gen_movi_i64(dest, ctx->base.pc_next + disp);
+    uint64_t addr = ctx->base.pc_next + disp;
+    if (ctx->pcrel) {
+        tcg_gen_addi_i64(dest, cpu_pc, addr - ctx->base.pc_first);
+    } else {
+        tcg_gen_movi_i64(dest, addr);
+    }
 }
 
 static void gen_excp_1(int exception, int error_code)
@@ -433,8 +441,14 @@ static DisasJumpType gen_store_conditional(DisasContext *ctx, int ra, int rb,
 static void gen_goto_tb(DisasContext *ctx, int idx, int32_t disp)
 {
     if (translator_use_goto_tb(&ctx->base, ctx->base.pc_next + disp)) {
+        /* With PCREL, PC must always be up-to-date. */
+        if (ctx->pcrel) {
+            gen_pc_disp(ctx, cpu_pc, disp);
+            tcg_gen_goto_tb(idx);
+        } else {
             tcg_gen_goto_tb(idx);
             gen_pc_disp(ctx, cpu_pc, disp);
+        }
         tcg_gen_exit_tb(ctx->base.tb, idx);
     } else {
         gen_pc_disp(ctx, cpu_pc, disp);
@@ -2852,6 +2866,7 @@ static void alpha_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cpu)
 
     ctx->tbflags = ctx->base.tb->flags;
     ctx->mem_idx = alpha_env_mmu_index(env);
+    ctx->pcrel = ctx->base.tb->cflags & CF_PCREL;
     ctx->implver = env->implver;
     ctx->amask = env->amask;
 
@@ -2887,8 +2902,14 @@ static void alpha_tr_tb_start(DisasContextBase *db, CPUState *cpu)
 
 static void alpha_tr_insn_start(DisasContextBase *dcbase, CPUState *cpu)
 {
+    DisasContext *ctx = container_of(dcbase, DisasContext, base);
+
+    if (ctx->pcrel) {
+        tcg_gen_insn_start(dcbase->pc_next & ~TARGET_PAGE_MASK);
+    } else {
         tcg_gen_insn_start(dcbase->pc_next);
     }
+}
 
 static void alpha_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
 {