devtools/eigen
1
0
Fork 0
mirror of https://gitlab.com/libeigen/eigen.git synced 2026-04-10 11:34:33 +08:00
Code Issues Packages Projects Releases Wiki Activity

Fix TensorUInt128 division infinite loop on overflow

Browse Source 
libeigen/eigen!2300

Closes #3012

Co-authored-by: Pavel Guzenfeld <67074795+PavelGuzenfeld@users.noreply.github.com>
This commit is contained in:
Pavel Guzenfeld
2026-03-20 15:41:00 +00:00
committed by Charles Schlosser
parent 3578883bb3
commit 821ab7d3e6
2 changed files with 23 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
unsupported/Eigen/src/Tensor/TensorUInt128.h
View File

@@ -200,14 +200,13 @@ static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE TensorUInt128<uint64_t, uint64_t> o
// calculate the biggest power of 2 times rhs that's less than or equal to lhs
TensorUInt128<uint64_t, uint64_t> power2(1);
TensorUInt128<uint64_t, uint64_t> d(rhs);
TensorUInt128<uint64_t, uint64_t> tmp(lhs - d);
while (lhs >= d) {
tmp = tmp - d;
if (d.high >> 63) break; // next doubling would overflow 128 bits
d = d + d;
power2 = power2 + power2;
}
tmp = TensorUInt128<uint64_t, uint64_t>(lhs.high, lhs.low);
TensorUInt128<uint64_t, uint64_t> tmp(lhs.high, lhs.low);
TensorUInt128<uint64_t, uint64_t> result(0);
while (power2 != TensorUInt128<static_val<0>, static_val<0>>(0)) {
if (tmp >= d) {

21
unsupported/test/cxx11_tensor_uint128.cpp
View File

@@ -124,6 +124,26 @@ void test_misc1() {
}
}
void test_div_overflow() {
// Regression test for infinite loop when lhs > 2^127 (issue #3012).
// Division would overflow d during doubling, causing an infinite loop.
TensorUInt128<uint64_t, uint64_t> a(1ULL << 63, 1);
TensorUInt128<uint64_t, uint64_t> b(2);
uint128_t expected = ((static_cast<uint128_t>(1ULL << 63) << 64) + 1) / 2;
VERIFY_EQUAL(a / b, expected);
// Also test with high bits in both operands
TensorUInt128<uint64_t, uint64_t> c(UINT64_MAX, UINT64_MAX);
TensorUInt128<uint64_t, uint64_t> d(1);
uint128_t c128 = (static_cast<uint128_t>(UINT64_MAX) << 64) | UINT64_MAX;
VERIFY_EQUAL(c / d, c128);
TensorUInt128<uint64_t, uint64_t> e(UINT64_MAX, UINT64_MAX);
TensorUInt128<uint64_t, uint64_t> f(0, 3);
uint128_t e128 = (static_cast<uint128_t>(UINT64_MAX) << 64) | UINT64_MAX;
VERIFY_EQUAL(e / f, e128 / 3);
}
void test_misc2() {
int64_t incr = internal::random<int64_t>(1, 100);
for (int64_t log_div = 0; log_div < 63; ++log_div) {
@@ -153,5 +173,6 @@ EIGEN_DECLARE_TEST(cxx11_tensor_uint128) {
CALL_SUBTEST_4(test_div());
CALL_SUBTEST_5(test_misc1());
CALL_SUBTEST_6(test_misc2());
CALL_SUBTEST_7(test_div_overflow());
#endif
}