target/riscv: Compute mstatus.sd on demand

The position of this read-only field is dependent on the current xlen.
Rather than having to compute that difference in many places, compute
it only on read.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20211020031709.359469-16-richard.henderson@linaro.org
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu_helper.c

@@ -185,10 +185,9 @@ bool riscv_cpu_fp_enabled(CPURISCVState *env)
 
 void riscv_cpu_swap_hypervisor_regs(CPURISCVState *env)
 {
-    uint64_t sd = riscv_cpu_mxl(env) == MXL_RV32 ? MSTATUS32_SD : MSTATUS64_SD;
     uint64_t mstatus_mask = MSTATUS_MXR | MSTATUS_SUM | MSTATUS_FS |
                             MSTATUS_SPP | MSTATUS_SPIE | MSTATUS_SIE |
-                            MSTATUS64_UXL | sd;
+                            MSTATUS64_UXL;
     bool current_virt = riscv_cpu_virt_enabled(env);
 
     g_assert(riscv_has_ext(env, RVH));

target/riscv/csr.c

@@ -477,10 +477,28 @@ static RISCVException read_mhartid(CPURISCVState *env, int csrno,
 }
 
 /* Machine Trap Setup */
+
+/* We do not store SD explicitly, only compute it on demand. */
+static uint64_t add_status_sd(RISCVMXL xl, uint64_t status)
+{
+    if ((status & MSTATUS_FS) == MSTATUS_FS ||
+        (status & MSTATUS_XS) == MSTATUS_XS) {
+        switch (xl) {
+        case MXL_RV32:
+            return status | MSTATUS32_SD;
+        case MXL_RV64:
+            return status | MSTATUS64_SD;
+        default:
+            g_assert_not_reached();
+        }
+    }
+    return status;
+}
+
 static RISCVException read_mstatus(CPURISCVState *env, int csrno,
                                    target_ulong *val)
 {
-    *val = env->mstatus;
+    *val = add_status_sd(riscv_cpu_mxl(env), env->mstatus);
     return RISCV_EXCP_NONE;
 }
 
@@ -498,7 +516,6 @@ static RISCVException write_mstatus(CPURISCVState *env, int csrno,
 {
     uint64_t mstatus = env->mstatus;
     uint64_t mask = 0;
-    int dirty;
 
     /* flush tlb on mstatus fields that affect VM */
     if ((val ^ mstatus) & (MSTATUS_MXR | MSTATUS_MPP | MSTATUS_MPV |
@@ -520,12 +537,7 @@ static RISCVException write_mstatus(CPURISCVState *env, int csrno,
 
     mstatus = (mstatus & ~mask) | (val & mask);
 
-    dirty = ((mstatus & MSTATUS_FS) == MSTATUS_FS) |
+    if (riscv_cpu_mxl(env) == MXL_RV64) {
-            ((mstatus & MSTATUS_XS) == MSTATUS_XS);
-    if (riscv_cpu_mxl(env) == MXL_RV32) {
-        mstatus = set_field(mstatus, MSTATUS32_SD, dirty);
-    } else {
-        mstatus = set_field(mstatus, MSTATUS64_SD, dirty);
         /* SXL and UXL fields are for now read only */
         mstatus = set_field(mstatus, MSTATUS64_SXL, MXL_RV64);
         mstatus = set_field(mstatus, MSTATUS64_UXL, MXL_RV64);
@@ -798,13 +810,8 @@ static RISCVException read_sstatus(CPURISCVState *env, int csrno,
 {
     target_ulong mask = (sstatus_v1_10_mask);
 
-    if (riscv_cpu_mxl(env) == MXL_RV32) {
+    /* TODO: Use SXL not MXL. */
-        mask |= SSTATUS32_SD;
+    *val = add_status_sd(riscv_cpu_mxl(env), env->mstatus & mask);
-    } else {
-        mask |= SSTATUS64_SD;
-    }
-
-    *val = env->mstatus & mask;
     return RISCV_EXCP_NONE;
 }
 

target/riscv/translate.c

@@ -280,7 +280,6 @@ static void gen_jal(DisasContext *ctx, int rd, target_ulong imm)
 static void mark_fs_dirty(DisasContext *ctx)
 {
     TCGv tmp;
-    target_ulong sd = get_xl(ctx) == MXL_RV32 ? MSTATUS32_SD : MSTATUS64_SD;
 
     if (ctx->mstatus_fs != MSTATUS_FS) {
         /* Remember the state change for the rest of the TB. */
@@ -288,7 +287,7 @@ static void mark_fs_dirty(DisasContext *ctx)
 
         tmp = tcg_temp_new();
         tcg_gen_ld_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
-        tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS | sd);
+        tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS);
         tcg_gen_st_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
         tcg_temp_free(tmp);
     }
@@ -299,7 +298,7 @@ static void mark_fs_dirty(DisasContext *ctx)
 
         tmp = tcg_temp_new();
         tcg_gen_ld_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus_hs));
-        tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS | sd);
+        tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS);
         tcg_gen_st_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus_hs));
         tcg_temp_free(tmp);
     }