From 029a2083a293f55b7b3d56e16b1546c882d9299c Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Sat, 1 Feb 2025 16:39:07 +0000 Subject: fpu: Implement float_flag_input_denormal_used For the x86 and the Arm FEAT_AFP semantics, we need to be able to tell the target code that the FPU operation has used an input denormal. Implement this; when it happens we set the new float_flag_denormal_input_used. Note that we only set this when an input denormal is actually used by the operation: if the operation results in Invalid Operation or Divide By Zero or the result is a NaN because some other input was a NaN then we never needed to look at the input denormal and do not set denormal_input_used. We mostly do not need to adjust the hardfloat codepaths to deal with this flag, because almost all hardfloat operations are already gated on the input not being a denormal, and will fall back to softfloat for a denormal input. The only exception is the comparison operations, where we need to add the check for input denormals, which must now fall back to softfloat where they did not before. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson --- fpu/softfloat.c | 38 +++++++++++++++++++++++++++++++++----- 1 file changed, 33 insertions(+), 5 deletions(-) (limited to 'fpu/softfloat.c') diff --git a/fpu/softfloat.c b/fpu/softfloat.c index 03a604c38e..f4fed9bfda 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -2718,8 +2718,10 @@ static void parts_float_to_ahp(FloatParts64 *a, float_status *s) float16_params_ahp.frac_size + 1); break; - case float_class_normal: case float_class_denormal: + float_raise(float_flag_input_denormal_used, s); + break; + case float_class_normal: case float_class_zero: break; @@ -2733,6 +2735,9 @@ static void parts64_float_to_float(FloatParts64 *a, float_status *s) if (is_nan(a->cls)) { parts_return_nan(a, s); } + if (a->cls == float_class_denormal) { + float_raise(float_flag_input_denormal_used, s); + } } static void parts128_float_to_float(FloatParts128 *a, float_status *s) @@ -2740,6 +2745,9 @@ static void parts128_float_to_float(FloatParts128 *a, float_status *s) if (is_nan(a->cls)) { parts_return_nan(a, s); } + if (a->cls == float_class_denormal) { + float_raise(float_flag_input_denormal_used, s); + } } #define parts_float_to_float(P, S) \ @@ -2752,12 +2760,21 @@ static void parts_float_to_float_narrow(FloatParts64 *a, FloatParts128 *b, a->sign = b->sign; a->exp = b->exp; - if (is_anynorm(a->cls)) { + switch (a->cls) { + case float_class_denormal: + float_raise(float_flag_input_denormal_used, s); + /* fall through */ + case float_class_normal: frac_truncjam(a, b); - } else if (is_nan(a->cls)) { + break; + case float_class_snan: + case float_class_qnan: /* Discard the low bits of the NaN. */ a->frac = b->frac_hi; parts_return_nan(a, s); + break; + default: + break; } } @@ -2772,6 +2789,9 @@ static void parts_float_to_float_widen(FloatParts128 *a, FloatParts64 *b, if (is_nan(a->cls)) { parts_return_nan(a, s); } + if (a->cls == float_class_denormal) { + float_raise(float_flag_input_denormal_used, s); + } } float32 float16_to_float32(float16 a, bool ieee, float_status *s) @@ -4411,7 +4431,11 @@ float32_hs_compare(float32 xa, float32 xb, float_status *s, bool is_quiet) goto soft; } - float32_input_flush2(&ua.s, &ub.s, s); + if (unlikely(float32_is_denormal(ua.s) || float32_is_denormal(ub.s))) { + /* We may need to set the input_denormal_used flag */ + goto soft; + } + if (isgreaterequal(ua.h, ub.h)) { if (isgreater(ua.h, ub.h)) { return float_relation_greater; @@ -4461,7 +4485,11 @@ float64_hs_compare(float64 xa, float64 xb, float_status *s, bool is_quiet) goto soft; } - float64_input_flush2(&ua.s, &ub.s, s); + if (unlikely(float64_is_denormal(ua.s) || float64_is_denormal(ub.s))) { + /* We may need to set the input_denormal_used flag */ + goto soft; + } + if (isgreaterequal(ua.h, ub.h)) { if (isgreater(ua.h, ub.h)) { return float_relation_greater; -- cgit 1.4.1