printf: Fix floating-point rounding consistency for RTZ devices #2202
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1. In vector test, prepare RTZ answer for RTZ rounding.
2. In mixed_format_random test, for a given float 'arg', the test
previously used 'arg' directly to generate ref_str:
ref_str << str_sprintf(format, arg);
This approach incorrectly assumes:
(float) arg == to_fp(to_str(arg));
However, this assumption fails under RTZ rounding. For example:
arg = 0xC642549C
to_str(arg) = -12437.152343f
to_fp_rtz(-12437.152343f) = 0xC642549B (-0X1.84A936P+13)
to_fp_rte(-12437.152343f) = 0xC642549C (-0X1.84A938P+13)
To address this, the reference result is now computed based on the
literal float string rather than the original 'arg' value.
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Reviewing |
lakshmih
approved these changes
Jan 22, 2025
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Merging as discussed in the February 11th teleconference. |
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In vector test, prepare RTZ answer for RTZ rounding.
In mixed_format_random test, for a given float 'arg', the test previously used 'arg' directly to generate ref_str:
This approach incorrectly assumes:
However, this assumption fails under RTZ rounding. For example:
To address this, the reference result is now computed based on the literal float string rather than the original 'arg' value.