From: Frank Chang <frank.chang@sifive.com>

RISCVCPUImpliedExtsRule is created to store the implied rules.
'is_misa' flag is used to distinguish whether the rule is derived
from the MISA or other extensions.
'ext' stores the MISA bit if 'is_misa' is true. Otherwise, it stores
the offset of the extension defined in RISCVCPUConfig. 'ext' will also
serve as the key of the hash tables to look up the rule in the following
commit.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Jerry Zhang Jian <jerry.zhangjian@sifive.com>
---
 target/riscv/cpu.c |  8 ++++++++
 target/riscv/cpu.h | 17 +++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index cee6fc4a9a..c7e5cec7ef 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -2242,6 +2242,14 @@ RISCVCPUProfile *riscv_profiles[] = {
     NULL,
 };

+RISCVCPUImpliedExtsRule *riscv_misa_implied_rules[] = {
+    NULL
+};
+
+RISCVCPUImpliedExtsRule *riscv_ext_implied_rules[] = {
+    NULL
+};
+
 static Property riscv_cpu_properties[] = {
     DEFINE_PROP_BOOL("debug", RISCVCPU, cfg.debug, true),

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 1501868008..b8ebff6631 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -122,6 +122,23 @@ typedef enum {
     EXT_STATUS_DIRTY,
 } RISCVExtStatus;

+typedef struct riscv_cpu_implied_exts_rule RISCVCPUImpliedExtsRule;
+
+struct riscv_cpu_implied_exts_rule {
+    bool enabled;
+    /* True if this is a MISA implied rule. */
+    bool is_misa;
+    /* ext is MISA bit if is_misa flag is true, else extension offset. */
+    const uint32_t ext;
+    const uint32_t implied_misas;
+    const uint32_t implied_exts[];
+};
+
+extern RISCVCPUImpliedExtsRule *riscv_misa_implied_rules[];
+extern RISCVCPUImpliedExtsRule *riscv_ext_implied_rules[];
+
+#define RISCV_IMPLIED_EXTS_RULE_END -1
+
 #define MMU_USER_IDX 3

 #define MAX_RISCV_PMPS (16)
--
2.43.2