target/sh4: Implement fsrra

Signed-off-by: Richard Henderson <rth@twiddle.net>

Message-Id: <20170718200255.31647-27-rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

target/sh4/helper.h

@@ -37,6 +37,7 @@ DEF_HELPER_FLAGS_3(fsub_FT, TCG_CALL_NO_WG, f32, env, f32, f32)
 DEF_HELPER_FLAGS_3(fsub_DT, TCG_CALL_NO_WG, f64, env, f64, f64)
 DEF_HELPER_FLAGS_2(fsqrt_FT, TCG_CALL_NO_WG, f32, env, f32)
 DEF_HELPER_FLAGS_2(fsqrt_DT, TCG_CALL_NO_WG, f64, env, f64)
+DEF_HELPER_FLAGS_2(fsrra_FT, TCG_CALL_NO_WG, f32, env, f32)
 DEF_HELPER_FLAGS_2(ftrc_FT, TCG_CALL_NO_WG, i32, env, f32)
 DEF_HELPER_FLAGS_2(ftrc_DT, TCG_CALL_NO_WG, i32, env, f64)
 DEF_HELPER_3(fipr, void, env, i32, i32)

target/sh4/op_helper.c

@@ -406,6 +406,22 @@ float64 helper_fsqrt_DT(CPUSH4State *env, float64 t0)
     return t0;
 }
 
+float32 helper_fsrra_FT(CPUSH4State *env, float32 t0)
+{
+    set_float_exception_flags(0, &env->fp_status);
+    /* "Approximate" 1/sqrt(x) via actual computation.  */
+    t0 = float32_sqrt(t0, &env->fp_status);
+    t0 = float32_div(float32_one, t0, &env->fp_status);
+    /* Since this is supposed to be an approximation, an imprecision
+       exception is required.  One supposes this also follows the usual
+       IEEE rule that other exceptions take precidence.  */
+    if (get_float_exception_flags(&env->fp_status) == 0) {
+        set_float_exception_flags(float_flag_inexact, &env->fp_status);
+    }
+    update_fpscr(env, GETPC());
+    return t0;
+}
+
 float32 helper_fsub_FT(CPUSH4State *env, float32 t0, float32 t1)
 {
     set_float_exception_flags(0, &env->fp_status);

target/sh4/translate.c

@@ -1731,6 +1731,8 @@ static void _decode_opc(DisasContext * ctx)
 	return;
     case 0xf07d: /* fsrra FRn */
 	CHECK_FPU_ENABLED
+        CHECK_FPSCR_PR_0
+        gen_helper_fsrra_FT(FREG(B11_8), cpu_env, FREG(B11_8));
 	break;
     case 0xf08d: /* fldi0 FRn - FPSCR: R[PR] */
 	CHECK_FPU_ENABLED