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cxxrtl: Fix value::sshr

This commit is contained in:
Merry 2023-12-13 12:11:57 +00:00
parent ff53f3d2b6
commit ded63bedd5
2 changed files with 30 additions and 5 deletions
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11
backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
View File

@ -430,12 +430,12 @@ struct value : public expr_base<value<Bits>> {
// Detect shifts definitely large than Bits early.
for (size_t n = 1; n < amount.chunks; n++)
if (amount.data[n] != 0)
return {};
return (Signed && is_neg()) ? value<Bits>().bit_not() : value<Bits>();
// Past this point we can use the least significant chunk as the shift size.
size_t shift_chunks = amount.data[0] / chunk::bits;
size_t shift_bits = amount.data[0] % chunk::bits;
if (shift_chunks >= chunks)
return {};
return (Signed && is_neg()) ? value<Bits>().bit_not() : value<Bits>();
value<Bits> result;
chunk::type carry = 0;
for (size_t n = 0; n < chunks - shift_chunks; n++) {
@ -444,12 +444,13 @@ struct value : public expr_base<value<Bits>> {
: data[chunks - 1 - n] << (chunk::bits - shift_bits);
}
if (Signed && is_neg()) {
size_t top_chunk_idx = (Bits - shift_bits) / chunk::bits;
size_t top_chunk_bits = (Bits - shift_bits) % chunk::bits;
size_t top_chunk_idx = amount.data[0] > Bits ? 0 : (Bits - amount.data[0]) / chunk::bits;
size_t top_chunk_bits = amount.data[0] > Bits ? 0 : (Bits - amount.data[0]) % chunk::bits;
for (size_t n = top_chunk_idx + 1; n < chunks; n++)
result.data[n] = chunk::mask;
if (shift_bits != 0)
if (amount.data[0] != 0)
result.data[top_chunk_idx] |= chunk::mask << top_chunk_bits;
result.data[result.chunks - 1] &= result.msb_mask;
}
return result;
}

24
tests/cxxrtl/test_value.cc
View File

@ -12,4 +12,28 @@ int main()
cxxrtl::value<6> c = a.shl(b);
assert(c.get<uint64_t>() == 0);
}
{
// sshr of unreasonably large size should sign extend correctly
cxxrtl::value<64> a(0u, 0x80000000u);
cxxrtl::value<64> b(0u, 1u);
cxxrtl::value<64> c = a.sshr(b);
assert(c.get<uint64_t>() == 0xffffffffffffffffu);
}
{
// sshr of exteeding Bits should sign extend correctly
cxxrtl::value<8> a(0x80u);
cxxrtl::value<8> b(10u);
cxxrtl::value<8> c = a.sshr(b);
assert(c.get<uint64_t>() == 0xffu);
}
{
// Sign extension should occur correctly
cxxrtl::value<64> a(0x23456789u, 0x8abcdef1u);
cxxrtl::value<8> b(32u);
cxxrtl::value<64> c = a.sshr(b);
assert(c.get<uint64_t>() == 0xffffffff8abcdef1u);
}
}