RISC-V: Add mcycle/minstret support for -icount auto

Previously the mycycle/minstret CSRs and rdcycle/rdinstret
psuedo instructions would return the time as a proxy for an
increasing instruction counter in the absence of having a
precise instruction count. If QEMU is invoked with -icount,
the mcycle/minstret CSRs and rdcycle/rdinstret psuedo
instructions will return the instruction count.

Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: Michael Clark <mjc@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index c3a029afef..c0e6a044d3 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -1390,6 +1390,7 @@ static void gen_system(CPURISCVState *env, DisasContext *ctx, uint32_t opc,
         break;
     default:
         tcg_gen_movi_tl(imm_rs1, rs1);
+        gen_io_start();
         switch (opc) {
         case OPC_RISC_CSRRW:
             gen_helper_csrrw(dest, cpu_env, source1, csr_store);
@@ -1413,6 +1414,7 @@ static void gen_system(CPURISCVState *env, DisasContext *ctx, uint32_t opc,
             gen_exception_illegal(ctx);
             return;
         }
+        gen_io_end();
         gen_set_gpr(rd, dest);
         /* end tb since we may be changing priv modes, to get mmu_index right */
         tcg_gen_movi_tl(cpu_pc, ctx->next_pc);