[PULL 051/101] target/ppc: Add helper for frsqrtes

[Cédric Le Goater]

From: Richard Henderson <richard.henderson@linaro.org>

There is no double-rounding bug here, because the result is
merely an estimate to within 1 part in 32, but perform the
operation with float64r32_div for consistency.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211119160502.17432-33-richard.henderson@linaro.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
---
 target/ppc/helper.h                |  1 +
 target/ppc/fpu_helper.c            | 19 +++++++++++++++++++
 target/ppc/translate/fp-impl.c.inc |  3 +--
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/target/ppc/helper.h b/target/ppc/helper.h
index f70a3aefcbf4..48774fab1917 100644
--- a/target/ppc/helper.h
+++ b/target/ppc/helper.h
@@ -114,6 +114,7 @@ DEF_HELPER_2(fsqrts, f64, env, f64)
 DEF_HELPER_2(fre, i64, env, i64)
 DEF_HELPER_2(fres, i64, env, i64)
 DEF_HELPER_2(frsqrte, i64, env, i64)
+DEF_HELPER_2(frsqrtes, i64, env, i64)
 DEF_HELPER_4(fsel, i64, env, i64, i64, i64)
 
 DEF_HELPER_FLAGS_2(ftdiv, TCG_CALL_NO_RWG_SE, i32, i64, i64)
diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
index 4acc557c088a..83c8f2556cc7 100644
--- a/target/ppc/fpu_helper.c
+++ b/target/ppc/fpu_helper.c
@@ -896,6 +896,25 @@ float64 helper_frsqrte(CPUPPCState *env, float64 arg)
     return retd;
 }
 
+/* frsqrtes  - frsqrtes. */
+float64 helper_frsqrtes(CPUPPCState *env, float64 arg)
+{
+    /* "Estimate" the reciprocal with actual division.  */
+    float64 rets = float64_sqrt(arg, &env->fp_status);
+    float64 retd = float64r32_div(float64_one, rets, &env->fp_status);
+    int flags = get_float_exception_flags(&env->fp_status);
+
+    if (unlikely(flags & float_flag_invalid)) {
+        float_invalid_op_sqrt(env, flags, 1, GETPC());
+    }
+    if (unlikely(flags & float_flag_divbyzero)) {
+        /* Reciprocal of (square root of) zero.  */
+        float_zero_divide_excp(env, GETPC());
+    }
+
+    return retd;
+}
+
 /* fsel - fsel. */
 uint64_t helper_fsel(CPUPPCState *env, uint64_t arg1, uint64_t arg2,
                      uint64_t arg3)
diff --git a/target/ppc/translate/fp-impl.c.inc 
b/target/ppc/translate/fp-impl.c.inc
index bf56e35cb686..2baae5988fde 100644
--- a/target/ppc/translate/fp-impl.c.inc
+++ b/target/ppc/translate/fp-impl.c.inc
@@ -212,8 +212,7 @@ static void gen_frsqrtes(DisasContext *ctx)
     t1 = tcg_temp_new_i64();
     gen_reset_fpstatus();
     get_fpr(t0, rB(ctx->opcode));
-    gen_helper_frsqrte(t1, cpu_env, t0);
-    gen_helper_frsp(t1, cpu_env, t1);
+    gen_helper_frsqrtes(t1, cpu_env, t0);
     set_fpr(rD(ctx->opcode), t1);
     gen_compute_fprf_float64(t1);
     if (unlikely(Rc(ctx->opcode) != 0)) {
-- 
2.31.1