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[multibyte] Implement interpreter semantics for array loads #8934

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[multibyte] Implement interpreter semantics for array loads #8934

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197 changes: 164 additions & 33 deletions src/wasm-interpreter.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2455,24 +2455,135 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
data->values[i] = truncateForPacking(value.getSingleValue(), field);
return Flow();
}
// Reads a single byte at byte offset `subIndex` from an array element `elem`.
static uint8_t
readArrayByte(const Literal& elem, const Field& field, size_t subIndex) {
if (field.packedType == Field::i8) {
assert(subIndex == 0);
return static_cast<uint8_t>(elem.geti32());
} else if (field.packedType == Field::i16) {
assert(subIndex < 2);
uint32_t val = elem.geti32();
return static_cast<uint8_t>((val >> (subIndex * 8)) & 0xff);
} else if (field.type == Type::i32) {
assert(subIndex < 4);
uint32_t val = elem.geti32();
return static_cast<uint8_t>((val >> (subIndex * 8)) & 0xff);
} else if (field.type == Type::i64) {
assert(subIndex < 8);
uint64_t val = elem.geti64();
return static_cast<uint8_t>((val >> (subIndex * 8)) & 0xff);
} else if (field.type == Type::f32) {
assert(subIndex < 4);
uint32_t val = elem.reinterpreti32();
return static_cast<uint8_t>((val >> (subIndex * 8)) & 0xff);
} else if (field.type == Type::f64) {
assert(subIndex < 8);
uint64_t val = elem.reinterpreti64();
return static_cast<uint8_t>((val >> (subIndex * 8)) & 0xff);
} else if (field.type == Type::v128) {
assert(subIndex < 16);
auto v = elem.getv128();
return v[subIndex];
}
WASM_UNREACHABLE("invalid element type");
}

// Writes a single byte `byteVal` at byte offset `subIndex` into array element
// `elem`.
static void writeArrayByte(Literal& elem,
const Field& field,
size_t subIndex,
uint8_t byteVal) {
if (field.packedType == Field::i8) {
assert(subIndex == 0);
elem = Literal(static_cast<int32_t>(byteVal));
} else if (field.packedType == Field::i16) {
assert(subIndex < 2);
uint32_t val = elem.geti32();
val = (val & ~(0xffu << (subIndex * 8))) |
(static_cast<uint32_t>(byteVal) << (subIndex * 8));
elem = Literal(static_cast<int32_t>(val & 0xffff));
} else if (field.type == Type::i32) {
assert(subIndex < 4);
uint32_t val = elem.geti32();
val = (val & ~(0xffu << (subIndex * 8))) |
(static_cast<uint32_t>(byteVal) << (subIndex * 8));
elem = Literal(static_cast<int32_t>(val));
} else if (field.type == Type::i64) {
assert(subIndex < 8);
uint64_t val = elem.geti64();
val = (val & ~(0xffull << (subIndex * 8))) |
(static_cast<uint64_t>(byteVal) << (subIndex * 8));
elem = Literal(static_cast<int64_t>(val));
} else if (field.type == Type::f32) {
assert(subIndex < 4);
uint32_t val = elem.reinterpreti32();
val = (val & ~(0xffu << (subIndex * 8))) |
(static_cast<uint32_t>(byteVal) << (subIndex * 8));
elem = Literal(bit_cast<float>(val));
} else if (field.type == Type::f64) {
assert(subIndex < 8);
uint64_t val = elem.reinterpreti64();
val = (val & ~(0xffull << (subIndex * 8))) |
(static_cast<uint64_t>(byteVal) << (subIndex * 8));
elem = Literal(bit_cast<double>(val));
} else if (field.type == Type::v128) {
assert(subIndex < 16);
auto v = elem.getv128();
v[subIndex] = byteVal;
elem = Literal(v.data());
} else {
WASM_UNREACHABLE("invalid element type");
}
}

template<typename T>
static T unpackBytes(const uint8_t* bytes, unsigned count) {
T val = 0;
for (unsigned b = 0; b < count; ++b) {
val |= static_cast<T>(bytes[b]) << (b * 8);
}
return val;
}

template<typename T>
static void packBytes(T val, uint8_t* bytes, unsigned count) {
for (unsigned b = 0; b < count; ++b) {
bytes[b] = static_cast<uint8_t>((val >> (b * 8)) & 0xff);
}
}

Flow visitArrayLoad(ArrayLoad* curr) {
VISIT(ref, curr->ref)
VISIT(index, curr->index)
auto data = ref.getSingleValue().getGCData();
if (!data) {
trap("null ref");
}
Index i = index.getSingleValue().geti32();
size_t size = data->values.size();
if (i >= size || curr->bytes > (size - i)) {
uint64_t address = uint32_t(index.getSingleValue().geti32());
uint64_t ea = address + curr->offset;

auto field = curr->ref->type.getHeapType().getArray().element;
size_t elemSize = field.getByteSize();
uint64_t capacity = uint64_t(data->values.size()) * elemSize;

if (ea > capacity || curr->bytes > capacity - ea) {
trap("array oob");
}
uint64_t val = 0;

uint8_t loadedBytes[16] = {0};
assert(curr->bytes <= sizeof(loadedBytes));
for (unsigned b = 0; b < curr->bytes; ++b) {
val |= static_cast<uint64_t>(data->values[i + b].geti32()) << (b * 8);
uint64_t byteOffset = ea + b;
size_t k = byteOffset / elemSize;
size_t subIndex = byteOffset % elemSize;
loadedBytes[b] = readArrayByte(data->values[k], field, subIndex);
}

switch (curr->type.getBasic()) {
case Type::i32: {
uint32_t val = unpackBytes<uint32_t>(loadedBytes, curr->bytes);
int32_t sval = static_cast<int32_t>(val);
if (curr->signed_) {
if (curr->bytes == 1) {
Expand All @@ -2484,6 +2595,7 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
return Literal(sval);
}
case Type::i64: {
uint64_t val = unpackBytes<uint64_t>(loadedBytes, curr->bytes);
int64_t sval = static_cast<int64_t>(val);
if (curr->signed_) {
if (curr->bytes == 1) {
Expand All @@ -2497,10 +2609,15 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
return Literal(sval);
}
case Type::f32: {
return Literal(bit_cast<float>(static_cast<int32_t>(val)));
uint32_t val = unpackBytes<uint32_t>(loadedBytes, curr->bytes);
return Literal(bit_cast<float>(val));
}
case Type::f64: {
return Literal(bit_cast<double>(static_cast<int64_t>(val)));
uint64_t val = unpackBytes<uint64_t>(loadedBytes, curr->bytes);
return Literal(bit_cast<double>(val));
}
case Type::v128: {
return Literal(loadedBytes);
}
default:
WASM_UNREACHABLE("invalid type");
Expand All @@ -2515,42 +2632,56 @@ class ExpressionRunner : public OverriddenVisitor<SubType, Flow> {
if (!data) {
trap("null ref");
}
uint64_t address = uint32_t(index.getSingleValue().geti32());
uint64_t ea = address + curr->offset;

Index i = index.getSingleValue().geti32();
size_t size = data->values.size();
// Use subtraction to avoid overflow.
if (i >= size || curr->bytes > (size - i)) {
auto field = curr->ref->type.getHeapType().getArray().element;
size_t elemSize = field.getByteSize();
uint64_t capacity = uint64_t(data->values.size()) * elemSize;

if (ea > capacity || curr->bytes > capacity - ea) {
trap("array oob");
}

uint8_t bytesToStore[16] = {0};
assert(curr->bytes <= sizeof(bytesToStore));
switch (curr->value->type.getBasic()) {
case Type::i32:
writeBytes(
value.getSingleValue().geti32(), curr->bytes, i, data->values);
case Type::i32: {
packBytes(value.getSingleValue().geti32(), bytesToStore, curr->bytes);
break;
case Type::i64:
writeBytes(
value.getSingleValue().geti64(), curr->bytes, i, data->values);
}
case Type::i64: {
packBytes(value.getSingleValue().geti64(), bytesToStore, curr->bytes);
break;
case Type::f32:
writeBytes(value.getSingleValue().reinterpreti32(),
curr->bytes,
i,
data->values);
}
case Type::f32: {
packBytes(
value.getSingleValue().reinterpreti32(), bytesToStore, curr->bytes);
break;
case Type::f64:
writeBytes(value.getSingleValue().reinterpreti64(),
curr->bytes,
i,
data->values);
}
case Type::f64: {
packBytes(
value.getSingleValue().reinterpreti64(), bytesToStore, curr->bytes);
break;
case Type::v128:
writeBytes(
value.getSingleValue().getv128(), curr->bytes, i, data->values);
}
case Type::v128: {
auto v = value.getSingleValue().getv128();
for (unsigned b = 0; b < curr->bytes; ++b) {
bytesToStore[b] = v[b];
}
break;
case Type::none:
case Type::unreachable:
WASM_UNREACHABLE("unimp basic type");
}
default:
WASM_UNREACHABLE("invalid type");
}

for (unsigned b = 0; b < curr->bytes; ++b) {
uint64_t byteOffset = ea + b;
size_t k = byteOffset / elemSize;
size_t subIndex = byteOffset % elemSize;
writeArrayByte(data->values[k], field, subIndex, bytesToStore[b]);
}

return Flow();
}
Flow visitArrayLen(ArrayLen* curr) {
Expand Down
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