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[Enhancement] Update ReduceOp initialization values for integer types #614

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Merged
LeiWang1999 merged 2 commits into from
Jul 8, 2025
Merged

[Enhancement] Update ReduceOp initialization values for integer types #614

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[Enhancement] Update ReduceOp initialization values for integer types
LeiWang1999 Jul 7, 2025
a9f0fac
[Enhancement] Update ReduceOp to handle unsigned integer initializati…
LeiWang1999 Jul 7, 2025
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16 changes: 14 additions & 2 deletions src/op/reduce.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -44,15 +44,27 @@ ReduceOp::ReduceOp(Array<PrimExpr> args, BufferMap vmap) {
}

PrimExpr ReduceOp::MakeInitValue() const {
auto dst_dtype = dst->dtype;
auto is_int = dst_dtype.is_int();
auto bits = dst_dtype.bits();

switch (type) {
case ReduceType::kSum:
return make_zero(dst->dtype);
case ReduceType::kAbsSum:
return make_zero(dst->dtype);
case ReduceType::kMax:
return make_const(dst->dtype, -INFINITY);
if (is_int) {
return make_const(dst->dtype, -(1 << (bits - 1)));
} else {
return make_const(dst->dtype, -INFINITY);
}
Comment on lines +57 to +64

@gemini-code-assist gemini-code-assist Bot Jul 7, 2025

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critical

The current logic for kMax has a few issues:

  • Undefined Behavior: -(1 << (bits - 1)) can lead to undefined behavior for bits >= 32 due to integer overflow on the 1 literal. For bits == 64, -(1LL << 63) is also undefined behavior due to negating the most negative number.
  • Missing Unsigned Integer Support: The logic doesn't handle unsigned integers (is_uint). For a kMax reduction, the initial value for an unsigned type should be 0.
Suggested change
if (is_int) {
return make_const(dst->dtype, -(1 << (bits - 1)));
} else {
return make_const(dst->dtype, -INFINITY);
}
if (is_int) {
// Handle 64-bit case separately to avoid overflow/UB.
if (bits == 64) {
// This is a portable way to represent INT64_MIN.
return make_const(dst_dtype, -9223372036854775807LL - 1);
}
return make_const(dst_dtype, -(1LL << (bits - 1)));
} else if (dst_dtype.is_uint()) {
return make_zero(dst_dtype);
} else {
return make_const(dst_dtype, -INFINITY);
}

case ReduceType::kMin:
return make_const(dst->dtype, INFINITY);
if (is_int) {
return make_const(dst->dtype, (1 << (bits - 1)) - 1);
} else {
return make_const(dst->dtype, INFINITY);
}
Comment on lines +63 to +72

@gemini-code-assist gemini-code-assist Bot Jul 7, 2025

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high

Similar to the kMax case, this logic has issues:

  • Undefined Behavior: (1 << (bits - 1)) can be undefined behavior for bits >= 32. You should use a 64-bit literal like 1LL or 1ULL to avoid this.
  • Missing Unsigned Integer Support: Unsigned integers are not handled. The initial value for a kMin reduction on an unsigned type should be the maximum value for that type.
Suggested change
if (is_int) {
return make_const(dst->dtype, (1 << (bits - 1)) - 1);
} else {
return make_const(dst->dtype, INFINITY);
}
if (is_int) {
// Use unsigned long long for the shift to avoid signed overflow UB.
// The result is correctly cast to int64_t for make_const.
return make_const(dst_dtype, static_cast<int64_t>((1ULL << (bits - 1)) - 1));
} else if (dst_dtype.is_uint()) {
if (bits == 64) {
// This is UINT64_MAX.
return make_const(dst_dtype, 18446744073709551615ULL);
}
return make_const(dst_dtype, (1ULL << bits) - 1);
} else {
return make_const(dst_dtype, INFINITY);
}

case ReduceType::kAbsMax:
return make_const(dst->dtype, 0);
default:
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