cpu: Introduce CPUNegativeOffsetState

Nothing in there so far, but all of the plumbing done
within the target ArchCPU state.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

include/exec/cpu-all.h

@@ -404,4 +404,28 @@ static inline CPUState *env_cpu(CPUArchState *env)
     return &env_archcpu(env)->parent_obj;
 }
 
+/**
+ * env_neg(env)
+ * @env: The architecture environment
+ *
+ * Return the CPUNegativeOffsetState associated with the environment.
+ */
+static inline CPUNegativeOffsetState *env_neg(CPUArchState *env)
+{
+    ArchCPU *arch_cpu = container_of(env, ArchCPU, env);
+    return &arch_cpu->neg;
+}
+
+/**
+ * cpu_neg(cpu)
+ * @cpu: The generic CPUState
+ *
+ * Return the CPUNegativeOffsetState associated with the cpu.
+ */
+static inline CPUNegativeOffsetState *cpu_neg(CPUState *cpu)
+{
+    ArchCPU *arch_cpu = container_of(cpu, ArchCPU, parent_obj);
+    return &arch_cpu->neg;
+}
+
 #endif /* CPU_ALL_H */

include/exec/cpu-defs.h

@@ -227,4 +227,12 @@ typedef struct CPUTLB {
 
 #endif  /* !CONFIG_USER_ONLY && CONFIG_TCG */
 
+/*
+ * This structure must be placed in ArchCPU immedately
+ * before CPUArchState, as a field named "neg".
+ */
+typedef struct CPUNegativeOffsetState {
+    /* Empty */
+} CPUNegativeOffsetState;
+
 #endif