[Qemu-devel] [PULL 21/38] target-arm: Add set_neon_rmode helper

[Peter Maydell <peter.maydell@linaro.org>]

From: Will Newton <will.newton@linaro.org>

This helper sets the rounding mode in the standard_fp_status word to
allow NEON instructions to modify the rounding mode whilst using the
standard FPSCR values for everything else.

Signed-off-by: Will Newton <will.newton@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/helper.c | 17 +++++++++++++++++
 target-arm/helper.h |  1 +
 2 files changed, 18 insertions(+)

diff --git a/target-arm/helper.c b/target-arm/helper.c
index b1541b9..ca5b000 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -4048,6 +4048,23 @@ uint32_t HELPER(set_rmode)(uint32_t rmode, CPUARMState *env)
     return prev_rmode;
 }
 
+/* Set the current fp rounding mode in the standard fp status and return
+ * the old one. This is for NEON instructions that need to change the
+ * rounding mode but wish to use the standard FPSCR values for everything
+ * else. Always set the rounding mode back to the correct value after
+ * modifying it.
+ * The argument is a softfloat float_round_ value.
+ */
+uint32_t HELPER(set_neon_rmode)(uint32_t rmode, CPUARMState *env)
+{
+    float_status *fp_status = &env->vfp.standard_fp_status;
+
+    uint32_t prev_rmode = get_float_rounding_mode(fp_status);
+    set_float_rounding_mode(rmode, fp_status);
+
+    return prev_rmode;
+}
+
 /* Half precision conversions.  */
 static float32 do_fcvt_f16_to_f32(uint32_t a, CPUARMState *env, float_status *s)
 {
diff --git a/target-arm/helper.h b/target-arm/helper.h
index 70872df..71b8411 100644
--- a/target-arm/helper.h
+++ b/target-arm/helper.h
@@ -149,6 +149,7 @@ DEF_HELPER_3(vfp_ultod, f64, i64, i32, ptr)
 DEF_HELPER_3(vfp_uqtod, f64, i64, i32, ptr)
 
 DEF_HELPER_FLAGS_2(set_rmode, TCG_CALL_NO_RWG, i32, i32, env)
+DEF_HELPER_FLAGS_2(set_neon_rmode, TCG_CALL_NO_RWG, i32, i32, env)
 
 DEF_HELPER_2(vfp_fcvt_f16_to_f32, f32, i32, env)
 DEF_HELPER_2(vfp_fcvt_f32_to_f16, i32, f32, env)
-- 
1.8.5