target/riscv: add "set round to odd" rounding mode helper function

helper_set_rounding_mode() is responsible for SIGILL, and "round to odd"
should be an interface private to translation, so add a new independent
helper_set_rod_rounding_mode().

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20211210075704.23951-64-frank.chang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/fpu_helper.c

@@ -81,6 +81,11 @@ void helper_set_rounding_mode(CPURISCVState *env, uint32_t rm)
     set_float_rounding_mode(softrm, &env->fp_status);
 }
 
+void helper_set_rod_rounding_mode(CPURISCVState *env)
+{
+    set_float_rounding_mode(float_round_to_odd, &env->fp_status);
+}
+
 static uint64_t do_fmadd_h(CPURISCVState *env, uint64_t rs1, uint64_t rs2,
                            uint64_t rs3, int flags)
 {

target/riscv/helper.h

@@ -3,6 +3,7 @@ DEF_HELPER_2(raise_exception, noreturn, env, i32)
 
 /* Floating Point - rounding mode */
 DEF_HELPER_FLAGS_2(set_rounding_mode, TCG_CALL_NO_WG, void, env, i32)
+DEF_HELPER_FLAGS_1(set_rod_rounding_mode, TCG_CALL_NO_WG, void, env)
 
 /* Floating Point - fused */
 DEF_HELPER_FLAGS_4(fmadd_s, TCG_CALL_NO_RWG, i64, env, i64, i64, i64)

target/riscv/internals.h

@@ -43,6 +43,7 @@ enum {
     RISCV_FRM_RUP = 3,  /* Round Up */
     RISCV_FRM_RMM = 4,  /* Round to Nearest, ties to Max Magnitude */
     RISCV_FRM_DYN = 7,  /* Dynamic rounding mode */
+    RISCV_FRM_ROD = 8,  /* Round to Odd */
 };
 
 static inline uint64_t nanbox_s(float32 f)

target/riscv/translate.c

@@ -30,6 +30,7 @@
 #include "exec/log.h"
 
 #include "instmap.h"
+#include "internals.h"
 
 /* global register indices */
 static TCGv cpu_gpr[32], cpu_pc, cpu_vl;
@@ -403,6 +404,12 @@ static void gen_set_rm(DisasContext *ctx, int rm)
         return;
     }
     ctx->frm = rm;
+
+    if (rm == RISCV_FRM_ROD) {
+        gen_helper_set_rod_rounding_mode(cpu_env);
+        return;
+    }
+
     gen_helper_set_rounding_mode(cpu_env, tcg_constant_i32(rm));
 }