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authorChristophe Lyon <christophe.lyon@st.com>2011-02-21 17:38:47 +0100
committerAurelien Jarno <aurelien@aurel32.net>2011-02-24 08:53:36 +0100
commitfe0e4872e46a5264ea433a22a793538545108564 (patch)
tree3181efeba9558c868f437f4bb372001017f160c3
parent56bf4fe2978e3e14c976feae825dbbd3700573d0 (diff)
target-arm: fix support for VRECPE.
Now use the same algorithm as described in the ARM ARM. Signed-off-by: Christophe Lyon <christophe.lyon@st.com> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
-rw-r--r--target-arm/helper.c83
1 files changed, 71 insertions, 12 deletions
diff --git a/target-arm/helper.c b/target-arm/helper.c
index 30c18090d2..031f2ecc62 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -2692,13 +2692,67 @@ float32 HELPER(rsqrts_f32)(float32 a, float32 b, CPUState *env)
#define float64_256 make_float64(0x4070000000000000LL)
#define float64_512 make_float64(0x4080000000000000LL)
-/* TODO: The architecture specifies the value that the estimate functions
- should return. We return the exact reciprocal/root instead. */
+/* The algorithm that must be used to calculate the estimate
+ * is specified by the ARM ARM.
+ */
+static float64 recip_estimate(float64 a, CPUState *env)
+{
+ float_status *s = &env->vfp.standard_fp_status;
+ /* q = (int)(a * 512.0) */
+ float64 q = float64_mul(float64_512, a, s);
+ int64_t q_int = float64_to_int64_round_to_zero(q, s);
+
+ /* r = 1.0 / (((double)q + 0.5) / 512.0) */
+ q = int64_to_float64(q_int, s);
+ q = float64_add(q, float64_half, s);
+ q = float64_div(q, float64_512, s);
+ q = float64_div(float64_one, q, s);
+
+ /* s = (int)(256.0 * r + 0.5) */
+ q = float64_mul(q, float64_256, s);
+ q = float64_add(q, float64_half, s);
+ q_int = float64_to_int64_round_to_zero(q, s);
+
+ /* return (double)s / 256.0 */
+ return float64_div(int64_to_float64(q_int, s), float64_256, s);
+}
+
float32 HELPER(recpe_f32)(float32 a, CPUState *env)
{
- float_status *s = &env->vfp.fp_status;
- float32 one = int32_to_float32(1, s);
- return float32_div(one, a, s);
+ float_status *s = &env->vfp.standard_fp_status;
+ float64 f64;
+ uint32_t val32 = float32_val(a);
+
+ int result_exp;
+ int a_exp = (val32 & 0x7f800000) >> 23;
+ int sign = val32 & 0x80000000;
+
+ if (float32_is_any_nan(a)) {
+ if (float32_is_signaling_nan(a)) {
+ float_raise(float_flag_invalid, s);
+ }
+ return float32_default_nan;
+ } else if (float32_is_infinity(a)) {
+ return float32_set_sign(float32_zero, float32_is_neg(a));
+ } else if (float32_is_zero_or_denormal(a)) {
+ float_raise(float_flag_divbyzero, s);
+ return float32_set_sign(float32_infinity, float32_is_neg(a));
+ } else if (a_exp >= 253) {
+ float_raise(float_flag_underflow, s);
+ return float32_set_sign(float32_zero, float32_is_neg(a));
+ }
+
+ f64 = make_float64((0x3feULL << 52)
+ | ((int64_t)(val32 & 0x7fffff) << 29));
+
+ result_exp = 253 - a_exp;
+
+ f64 = recip_estimate(f64, env);
+
+ val32 = sign
+ | ((result_exp & 0xff) << 23)
+ | ((float64_val(f64) >> 29) & 0x7fffff);
+ return make_float32(val32);
}
float32 HELPER(rsqrte_f32)(float32 a, CPUState *env)
@@ -2710,13 +2764,18 @@ float32 HELPER(rsqrte_f32)(float32 a, CPUState *env)
uint32_t HELPER(recpe_u32)(uint32_t a, CPUState *env)
{
- float_status *s = &env->vfp.fp_status;
- float32 tmp;
- tmp = int32_to_float32(a, s);
- tmp = float32_scalbn(tmp, -32, s);
- tmp = helper_recpe_f32(tmp, env);
- tmp = float32_scalbn(tmp, 31, s);
- return float32_to_int32(tmp, s);
+ float64 f64;
+
+ if ((a & 0x80000000) == 0) {
+ return 0xffffffff;
+ }
+
+ f64 = make_float64((0x3feULL << 52)
+ | ((int64_t)(a & 0x7fffffff) << 21));
+
+ f64 = recip_estimate (f64, env);
+
+ return 0x80000000 | ((float64_val(f64) >> 21) & 0x7fffffff);
}
uint32_t HELPER(rsqrte_u32)(uint32_t a, CPUState *env)