target/riscv: riscv_tr_init_disas_context: copy pointer-to-cfg into cfg_ptr

As the number of extensions is growing, copying them individiually
into the DisasContext will scale less and less... instead we populate
a pointer to the RISCVCPUConfig structure in the DisasContext.

This adds an extra indirection when checking for the availability of
an extension (compared to copying the fields into DisasContext).
While not a performance problem today, we can always (shallow) copy
the entire structure into the DisasContext (instead of putting a
pointer to it) if this is ever deemed necessary.

Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220202005249.3566542-3-philipp.tomsich@vrull.eu>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/translate.c

@@ -76,6 +76,7 @@ typedef struct DisasContext {
     int frm;
     RISCVMXL ol;
     bool virt_enabled;
+    const RISCVCPUConfig *cfg_ptr;
     bool ext_ifencei;
     bool ext_zfh;
     bool ext_zfhmin;
@@ -908,6 +909,7 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
 #endif
     ctx->misa_ext = env->misa_ext;
     ctx->frm = -1;  /* unknown rounding mode */
+    ctx->cfg_ptr = &(cpu->cfg);
     ctx->ext_ifencei = cpu->cfg.ext_ifencei;
     ctx->ext_zfh = cpu->cfg.ext_zfh;
     ctx->ext_zfhmin = cpu->cfg.ext_zfhmin;