gnu /
gcc /
b89ee9e63ce7dff24dfab95f8df123e71629f5ff dfp, real: Fix up FLOAT_EXPR/FIX_TRUNC_EXPR constant folding between dfp and large _BitInt [PR120631]
The following testcase shows that while at runtime we handle conversions
between _Decimal{64,128} and large _BitInt correctly, at compile time we
mishandle them in both directions, in one direction we end up in ICE in
decimal_from_integer callee because the char buffer is too short for the
needed number of decimal digits, in the conversion of dfp to large _BitInt
we return 0 in the wide_int.
The following patch fixes the ICE by using larger buffer (XALLOCAVEC
allocated, it will be never larger than 65536 / 3 bytes) in the larger
_BitInt case, and the other direction by setting exponent to exp % 19
and instead multiplying the result by needed powers of 10^19 (10^19 chosen
as largest power of ten that can fit into UHWI).
2025-06-18 Jakub Jelinek <jakub@redhat.com>
PR middle-end/120631
* real.cc (decimal_from_integer): Add digits argument, if larger than
256, use XALLOCAVEC allocated buffer.
(real_from_integer): Pass val_in's precision divided by 3 to
decimal_from_integer.
* dfp.cc (decimal_real_to_integer): For precision > 128 if finite
and exponent is large, decrease exponent and multiply resulting
wide_int by powers of 10^19.
* gcc.dg/dfp/bitint-9.c: New test.
(cherry picked from commit f3002d664d1137844c714645a841a48ab57d0eaa)
3 files changed
