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| author | Andy Knowles <andy.knowles@gmail.com> | 2020-08-12 11:32:57 +0200 |
|---|---|---|
| committer | Andy Knowles <andy.knowles@gmail.com> | 2020-08-12 11:32:57 +0200 |
| commit | 1227c3681be8e6365e91e77b06dcbe58ff6c7593 (patch) | |
| tree | 5c71baa228456d2a286d1788b8261e609801de11 /backends/cxxrtl | |
| parent | 04f6158bf2ce9a95970f1be435351786f59bed92 (diff) | |
| download | yosys-1227c3681be8e6365e91e77b06dcbe58ff6c7593.tar.gz yosys-1227c3681be8e6365e91e77b06dcbe58ff6c7593.tar.bz2 yosys-1227c3681be8e6365e91e77b06dcbe58ff6c7593.zip | |
cxxrtl.h: Fix incorrect CarryOut in alu when Bits % 32 != 0 && Invert == False
Diffstat (limited to 'backends/cxxrtl')
| -rw-r--r-- | backends/cxxrtl/cxxrtl.h | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/backends/cxxrtl/cxxrtl.h b/backends/cxxrtl/cxxrtl.h index f0d7b9fc7..dfdb49929 100644 --- a/backends/cxxrtl/cxxrtl.h +++ b/backends/cxxrtl/cxxrtl.h @@ -450,12 +450,18 @@ struct value : public expr_base<value<Bits>> { std::pair<value<Bits>, bool /*CarryOut*/> alu(const value<Bits> &other) const { value<Bits> result; bool carry = CarryIn; - for (size_t n = 0; n < result.chunks; n++) { + // Handle full chunks first + for (size_t n = 0; n < result.chunks - 1; n++) { result.data[n] = data[n] + (Invert ? ~other.data[n] : other.data[n]) + carry; carry = (result.data[n] < data[n]) || (result.data[n] == data[n] && carry); } - result.data[result.chunks - 1] &= result.msb_mask; + // Handle last chunk (mask before updating carry) + constexpr size_t last = result.chunks - 1; + result.data[last] = data[last] + (Invert ? ~other.data[last] : other.data[last]) + carry; + result.data[last] &= result.msb_mask; + carry = (result.data[last] < data[last]) || + (result.data[last] == data[last] && carry); return {result, carry}; } |