target-xtensa: add ICOUNT SR and debug exception

ICOUNT SR gets incremented on every instruction completion provided that
CINTLEVEL at the beginning of the instruction execution is lower than
ICOUNTLEVEL.

When ICOUNT would increment to 0 a debug exception is raised if
CINTLEVEL is lower than DEBUGLEVEL.

See ISA, 4.7.7.5 for more details.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

2 files changed, 54 insertions, 1 deletions

diff --git a/target-xtensa/cpu.h b/target-xtensa/cpu.h
index a18072b7bd..92441e34f9 100644
--- a/target-xtensa/cpu.h
+++ b/target-xtensa/cpu.h
@@ -142,6 +142,8 @@ enum {
     DEBUGCAUSE = 233,
     CCOUNT = 234,
     PRID = 235,
+    ICOUNT = 236,
+    ICOUNTLEVEL = 237,
     EXCVADDR = 238,
     CCOMPARE = 240,
 };
@@ -429,6 +431,7 @@ static inline int cpu_mmu_index(CPUState *env)
 #define XTENSA_TBFLAG_EXCM 0x4
 #define XTENSA_TBFLAG_LITBASE 0x8
 #define XTENSA_TBFLAG_DEBUG 0x10
+#define XTENSA_TBFLAG_ICOUNT 0x20
 
 static inline void cpu_get_tb_cpu_state(CPUState *env, target_ulong *pc,
         target_ulong *cs_base, int *flags)
@@ -448,6 +451,9 @@ static inline void cpu_get_tb_cpu_state(CPUState *env, target_ulong *pc,
         if (xtensa_get_cintlevel(env) < env->config->debug_level) {
             *flags |= XTENSA_TBFLAG_DEBUG;
         }
+        if (xtensa_get_cintlevel(env) < env->sregs[ICOUNTLEVEL]) {
+            *flags |= XTENSA_TBFLAG_ICOUNT;
+        }
     }
 }
 
diff --git a/target-xtensa/translate.c b/target-xtensa/translate.c
index a438474b47..3bf880f5cb 100644
--- a/target-xtensa/translate.c
+++ b/target-xtensa/translate.c
@@ -63,6 +63,8 @@ typedef struct DisasContext {
     unsigned used_window;
 
     bool debug;
+    bool icount;
+    TCGv_i32 next_icount;
 } DisasContext;
 
 static TCGv_ptr cpu_env;
@@ -127,6 +129,8 @@ static const char * const sregnames[256] = {
     [DEBUGCAUSE] = "DEBUGCAUSE",
     [CCOUNT] = "CCOUNT",
     [PRID] = "PRID",
+    [ICOUNT] = "ICOUNT",
+    [ICOUNTLEVEL] = "ICOUNTLEVEL",
     [EXCVADDR] = "EXCVADDR",
     [CCOMPARE] = "CCOMPARE0",
     [CCOMPARE + 1] = "CCOMPARE1",
@@ -313,10 +317,13 @@ static void gen_check_privilege(DisasContext *dc)
 static void gen_jump_slot(DisasContext *dc, TCGv dest, int slot)
 {
     tcg_gen_mov_i32(cpu_pc, dest);
+    gen_advance_ccount(dc);
+    if (dc->icount) {
+        tcg_gen_mov_i32(cpu_SR[ICOUNT], dc->next_icount);
+    }
     if (dc->singlestep_enabled) {
         gen_exception(dc, EXCP_DEBUG);
     } else {
-        gen_advance_ccount(dc);
         if (slot >= 0) {
             tcg_gen_goto_tb(slot);
             tcg_gen_exit_tb((tcg_target_long)dc->tb + slot);
@@ -580,6 +587,22 @@ static void gen_wsr_prid(DisasContext *dc, uint32_t sr, TCGv_i32 v)
 {
 }
 
+static void gen_wsr_icount(DisasContext *dc, uint32_t sr, TCGv_i32 v)
+{
+    if (dc->icount) {
+        tcg_gen_mov_i32(dc->next_icount, v);
+    } else {
+        tcg_gen_mov_i32(cpu_SR[sr], v);
+    }
+}
+
+static void gen_wsr_icountlevel(DisasContext *dc, uint32_t sr, TCGv_i32 v)
+{
+    tcg_gen_andi_i32(cpu_SR[sr], v, 0xf);
+    /* This can change tb->flags, so exit tb */
+    gen_jumpi_check_loop_end(dc, -1);
+}
+
 static void gen_wsr_ccompare(DisasContext *dc, uint32_t sr, TCGv_i32 v)
 {
     uint32_t id = sr - CCOMPARE;
@@ -617,6 +640,8 @@ static void gen_wsr(DisasContext *dc, uint32_t sr, TCGv_i32 s)
         [PS] = gen_wsr_ps,
         [DEBUGCAUSE] = gen_wsr_debugcause,
         [PRID] = gen_wsr_prid,
+        [ICOUNT] = gen_wsr_icount,
+        [ICOUNTLEVEL] = gen_wsr_icountlevel,
         [CCOMPARE] = gen_wsr_ccompare,
         [CCOMPARE + 1] = gen_wsr_ccompare,
         [CCOMPARE + 2] = gen_wsr_ccompare,
@@ -2493,10 +2518,14 @@ static void gen_intermediate_code_internal(
     dc.is_jmp = DISAS_NEXT;
     dc.ccount_delta = 0;
     dc.debug = tb->flags & XTENSA_TBFLAG_DEBUG;
+    dc.icount = tb->flags & XTENSA_TBFLAG_ICOUNT;
 
     init_litbase(&dc);
     init_sar_tracker(&dc);
     reset_used_window(&dc);
+    if (dc.icount) {
+        dc.next_icount = tcg_temp_local_new_i32();
+    }
 
     gen_icount_start();
 
@@ -2532,12 +2561,27 @@ static void gen_intermediate_code_internal(
             gen_io_start();
         }
 
+        if (dc.icount) {
+            int label = gen_new_label();
+
+            tcg_gen_addi_i32(dc.next_icount, cpu_SR[ICOUNT], 1);
+            tcg_gen_brcondi_i32(TCG_COND_NE, dc.next_icount, 0, label);
+            tcg_gen_mov_i32(dc.next_icount, cpu_SR[ICOUNT]);
+            if (dc.debug) {
+                gen_debug_exception(&dc, DEBUGCAUSE_IC);
+            }
+            gen_set_label(label);
+        }
+
         if (dc.debug) {
             gen_ibreak_check(env, &dc);
         }
 
         disas_xtensa_insn(&dc);
         ++insn_count;
+        if (dc.icount) {
+            tcg_gen_mov_i32(cpu_SR[ICOUNT], dc.next_icount);
+        }
         if (env->singlestep_enabled) {
             tcg_gen_movi_i32(cpu_pc, dc.pc);
             gen_exception(&dc, EXCP_DEBUG);
@@ -2550,6 +2594,9 @@ static void gen_intermediate_code_internal(
 
     reset_litbase(&dc);
     reset_sar_tracker(&dc);
+    if (dc.icount) {
+        tcg_temp_free(dc.next_icount);
+    }
 
     if (tb->cflags & CF_LAST_IO) {
         gen_io_end();