target/arm: Plumb FEAT_RPRES frecpe and frsqrte through to new helper

FEAT_RPRES implements an "increased precision" variant of the single
precision FRECPE and FRSQRTE instructions from an 8 bit to a 12
bit mantissa. This applies only when FPCR.AH == 1. Note that the
halfprec and double versions of these insns retain the 8 bit
precision regardless.

In this commit we add all the plumbing to make these instructions
call a new helper function when the increased-precision is in
effect. In the following commit we will provide the actual change
in behaviour in the helpers.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 30 insertions, 2 deletions

diff --git a/target/arm/vfp_helper.c b/target/arm/vfp_helper.c
index 5c370e2..b97417e 100644
--- a/target/arm/vfp_helper.c
+++ b/target/arm/vfp_helper.c
@@ -841,7 +841,11 @@ uint32_t HELPER(recpe_f16)(uint32_t input, float_status *fpst)
     return make_float16(f16_val);
 }
 
-float32 HELPER(recpe_f32)(float32 input, float_status *fpst)
+/*
+ * FEAT_RPRES means the f32 FRECPE has an "increased precision" variant
+ * which is used when FPCR.AH == 1.
+ */
+static float32 do_recpe_f32(float32 input, float_status *fpst, bool rpres)
 {
     float32 f32 = float32_squash_input_denormal(input, fpst);
     uint32_t f32_val = float32_val(f32);
@@ -890,6 +894,16 @@ float32 HELPER(recpe_f32)(float32 input, float_status *fpst)
     return make_float32(f32_val);
 }
 
+float32 HELPER(recpe_f32)(float32 input, float_status *fpst)
+{
+    return do_recpe_f32(input, fpst, false);
+}
+
+float32 HELPER(recpe_rpres_f32)(float32 input, float_status *fpst)
+{
+    return do_recpe_f32(input, fpst, true);
+}
+
 float64 HELPER(recpe_f64)(float64 input, float_status *fpst)
 {
     float64 f64 = float64_squash_input_denormal(input, fpst);
@@ -1035,7 +1049,11 @@ uint32_t HELPER(rsqrte_f16)(uint32_t input, float_status *s)
     return make_float16(val);
 }
 
-float32 HELPER(rsqrte_f32)(float32 input, float_status *s)
+/*
+ * FEAT_RPRES means the f32 FRSQRTE has an "increased precision" variant
+ * which is used when FPCR.AH == 1.
+ */
+static float32 do_rsqrte_f32(float32 input, float_status *s, bool rpres)
 {
     float32 f32 = float32_squash_input_denormal(input, s);
     uint32_t val = float32_val(f32);
@@ -1080,6 +1098,16 @@ float32 HELPER(rsqrte_f32)(float32 input, float_status *s)
     return make_float32(val);
 }
 
+float32 HELPER(rsqrte_f32)(float32 input, float_status *s)
+{
+    return do_rsqrte_f32(input, s, false);
+}
+
+float32 HELPER(rsqrte_rpres_f32)(float32 input, float_status *s)
+{
+    return do_rsqrte_f32(input, s, true);
+}
+
 float64 HELPER(rsqrte_f64)(float64 input, float_status *s)
 {
     float64 f64 = float64_squash_input_denormal(input, s);