target-arm: Ignore most exceptions from scalbn when doing fixpoint conversion
The VFP fixed point conversion helpers first call float_scalbn and then convert the result to an integer. This scalbn operation may set floating point exception flags for: * overflow & inexact (if it overflows to infinity) * input denormal squashed to zero * output denormal squashed to zero Of these, we only care about the input-denormal flag, since the output of the whole scale-and-convert operation will be an integer (so squashed-output-denormal and overflow don't apply). Suppress the others by saving the pre-scalb exception flags and only copying across a potential input-denormal flag. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <rth@twiddle.net>
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@ -3986,18 +3986,27 @@ float##fsz HELPER(vfp_##name##to##p)(uint##isz##_t x, uint32_t shift, \
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return float##fsz##_scalbn(tmp, -(int)shift, fpst); \
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}
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/* Notice that we want only input-denormal exception flags from the
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* scalbn operation: the other possible flags (overflow+inexact if
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* we overflow to infinity, output-denormal) aren't correct for the
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* complete scale-and-convert operation.
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*/
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#define VFP_CONV_FLOAT_FIX_ROUND(name, p, fsz, isz, itype, round) \
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uint##isz##_t HELPER(vfp_to##name##p##round)(float##fsz x, \
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uint32_t shift, \
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void *fpstp) \
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{ \
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float_status *fpst = fpstp; \
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int old_exc_flags = get_float_exception_flags(fpst); \
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float##fsz tmp; \
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if (float##fsz##_is_any_nan(x)) { \
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float_raise(float_flag_invalid, fpst); \
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return 0; \
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} \
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tmp = float##fsz##_scalbn(x, shift, fpst); \
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old_exc_flags |= get_float_exception_flags(fpst) \
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& float_flag_input_denormal; \
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set_float_exception_flags(old_exc_flags, fpst); \
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return float##fsz##_to_##itype##round(tmp, fpst); \
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}
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