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Merged
veblush merged 1 commit into from
Jan 22, 2026
Merged

Automated sync from github.com/tensorflow/tensorflow #3317

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52 changes: 36 additions & 16 deletions tensorflow/lite/kernels/internal/portable_tensor_utils.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,8 @@ void UnpackDenseInt4IntoInt8(const int8_t* src_buffer, int num_elements,
}

void UnpackPackedIntToInt8(const int8_t* src_buffer, int num_elements,
int bit_width, int8_t* dst_buffer) {
int bit_width, int8_t* dst_buffer,
bool unpack_unsigned) {
assert(bit_width == 2 || bit_width == 4);
if (bit_width == 4) {
// num_elements means the number of elements regardless of packed or
Expand All @@ -105,39 +106,58 @@ void UnpackPackedIntToInt8(const int8_t* src_buffer, int num_elements,
//. stored in dst_buffer[0], dst_buffer[1] and dst_buffer[2] (j = 0..2)
for (int i = 0; i < num_elements / 2; i++) {
int8_t byte = src_buffer[i];
// Shift left first so that sign is properly extended when shifted right
int8_t lower = static_cast<int8_t>(byte << 4) >> 4;
int8_t higher = byte >> 4;
int8_t lower, higher;
if (unpack_unsigned) {
lower = byte & 0x0F;
higher = (byte >> 4) & 0x0F;
} else {
// Shift left first so that sign is properly extended when shifted right
lower = static_cast<int8_t>(byte << 4) >> 4;
higher = byte >> 4;
}
dst_buffer[2 * i] = lower;
dst_buffer[2 * i + 1] = higher;
}

// If the buffer size is odd, extract the final lower nibble.
if (num_elements % 2 != 0) {
int8_t byte = src_buffer[num_elements / 2];
dst_buffer[num_elements - 1] =
static_cast<int8_t>(src_buffer[num_elements / 2] << 4) >> 4;
unpack_unsigned ? (byte & 0x0F) : static_cast<int8_t>(byte << 4) >> 4;
}
} else if (bit_width == 2) {
for (int i = 0; i < num_elements / 4; i++) {
int8_t byte = src_buffer[i];
// Shift left first so that sign is properly extended when shifted right
int8_t val1 = static_cast<int8_t>(byte << 6) >> 6;
int8_t val2 = static_cast<int8_t>((byte << 4) & 0xFF) >> 6;
int8_t val3 = static_cast<int8_t>((byte << 2) & 0xFF) >> 6;
int8_t val4 = byte >> 6;
dst_buffer[4 * i] = val1;
dst_buffer[4 * i + 1] = val2;
dst_buffer[4 * i + 2] = val3;
dst_buffer[4 * i + 3] = val4;
if (unpack_unsigned) {
dst_buffer[4 * i] = byte & 0x03;
dst_buffer[4 * i + 1] = (byte >> 2) & 0x03;
dst_buffer[4 * i + 2] = (byte >> 4) & 0x03;
dst_buffer[4 * i + 3] = (byte >> 6) & 0x03;
} else {
// Shift left first so that sign is properly extended when shifted right
int8_t val1 = static_cast<int8_t>(byte << 6) >> 6;
int8_t val2 = static_cast<int8_t>((byte << 4) & 0xFF) >> 6;
int8_t val3 = static_cast<int8_t>((byte << 2) & 0xFF) >> 6;
int8_t val4 = byte >> 6;
dst_buffer[4 * i] = val1;
dst_buffer[4 * i + 1] = val2;
dst_buffer[4 * i + 2] = val3;
dst_buffer[4 * i + 3] = val4;
}
}

// Handle the remaining elements.
int remaining_elements = num_elements % 4;
if (remaining_elements > 0) {
int8_t byte = src_buffer[num_elements / 4];
for (int i = 0; i < remaining_elements; i++) {
dst_buffer[num_elements - remaining_elements + i] =
static_cast<int8_t>((byte << (6 - 2 * i)) & 0xFF) >> 6;
if (unpack_unsigned) {
dst_buffer[num_elements - remaining_elements + i] =
(byte >> (2 * i)) & 0x03;
} else {
dst_buffer[num_elements - remaining_elements + i] =
static_cast<int8_t>((byte << (6 - 2 * i)) & 0xFF) >> 6;
}
}
}
}
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3 changes: 2 additions & 1 deletion tensorflow/lite/kernels/internal/portable_tensor_utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -633,7 +633,8 @@ void UnpackDenseInt4IntoInt8(const int8_t* src_buffer, int num_elements,
// For 2-bit unpacking: e.g., `src_buffer = {0x12};` (num_elements = 4)
// will return `dst_buffer = {0x02, 0x00, 0x01, 0x00}` (sign extended).
void UnpackPackedIntToInt8(const int8_t* src_buffer, int num_elements,
int bit_width, int8_t* dst_buffer);
int bit_width, int8_t* dst_buffer,
bool unpack_unsigned = false);

// Pack `src_buffer` into a densely packed buffer of int2 or int4 values.
// Parameters:
Expand Down