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Merged
tlively merged 4 commits into from
Mar 7, 2025
Merged

Binary encoding and decoding of exact casts #7347

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1f46aeb
Binary encoding and decoding of exact casts
tlively Mar 5, 2025
b6c1f85
fix
tlively Mar 5, 2025
61cc44f
Only emit new ref.cast and ref.test when allowed
tlively Mar 6, 2025
186de57
name flags and fix test on windows
tlively Mar 6, 2025
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9 changes: 9 additions & 0 deletions src/wasm-binary.h
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Original file line number Diff line number Diff line change
Expand Up @@ -304,6 +304,13 @@ enum SegmentFlag {
UsesExpressions = 1 << 2
};

enum BrOnCastFlag {
InputNullable = 1 << 0,
OutputNullable = 1 << 1,
InputExact = 1 << 2,
OutputExact = 1 << 3,
};

enum EncodedType {
// value types
i32 = -0x1, // 0x7f
Expand Down Expand Up @@ -1126,6 +1133,8 @@ enum ASTNodes {
I31GetS = 0x1d,
I31GetU = 0x1e,
RefI31Shared = 0x1f,
RefTestRT = 0x20,
RefCastRT = 0x21,

// Shared GC Opcodes

Expand Down
18 changes: 16 additions & 2 deletions src/wasm/wasm-binary.cpp
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Expand Up @@ -4251,16 +4251,30 @@ Result<> WasmBinaryReader::readInst() {
return builder.makeRefTest(Type(getHeapType(), NonNullable));
case BinaryConsts::RefTestNull:
return builder.makeRefTest(Type(getHeapType(), Nullable));
case BinaryConsts::RefTestRT:
return builder.makeRefTest(getType());
case BinaryConsts::RefCast:
return builder.makeRefCast(Type(getHeapType(), NonNullable));
case BinaryConsts::RefCastNull:
return builder.makeRefCast(Type(getHeapType(), Nullable));
case BinaryConsts::RefCastRT:
return builder.makeRefCast(getType());
case BinaryConsts::BrOnCast:
case BinaryConsts::BrOnCastFail: {
auto flags = getInt8();
auto label = getU32LEB();
auto in = Type(getHeapType(), (flags & 1) ? Nullable : NonNullable);
auto cast = Type(getHeapType(), (flags & 2) ? Nullable : NonNullable);
auto srcNull = (flags & BinaryConsts::BrOnCastFlag::InputNullable)
? Nullable
: NonNullable;
auto dstNull = (flags & BinaryConsts::BrOnCastFlag::OutputNullable)
? Nullable
: NonNullable;
auto srcExact =
(flags & BinaryConsts::BrOnCastFlag::InputExact) ? Exact : Inexact;
auto dstExact =
(flags & BinaryConsts::BrOnCastFlag::OutputExact) ? Exact : Inexact;
auto in = Type(getHeapType(), srcNull, srcExact);
auto cast = Type(getHeapType(), dstNull, dstExact);
auto kind = op == BinaryConsts::BrOnCast ? BrOnCast : BrOnCastFail;
return builder.makeBrOn(label, kind, in, cast);
}
Expand Down
52 changes: 42 additions & 10 deletions src/wasm/wasm-stack.cpp
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Expand Up @@ -2260,22 +2260,38 @@ void BinaryInstWriter::visitCallRef(CallRef* curr) {

void BinaryInstWriter::visitRefTest(RefTest* curr) {
o << int8_t(BinaryConsts::GCPrefix);
if (curr->castType.isNullable()) {
o << U32LEB(BinaryConsts::RefTestNull);
if (curr->castType.isExact() &&
parent.getModule()->features.hasCustomDescriptors()) {
// Fall back to the general form with a reftype immediate.
o << U32LEB(BinaryConsts::RefTestRT);
parent.writeType(curr->castType);
} else {
o << U32LEB(BinaryConsts::RefTest);
// Use the special-case form with heap type immediate.
if (curr->castType.isNullable()) {
o << U32LEB(BinaryConsts::RefTestNull);
} else {
o << U32LEB(BinaryConsts::RefTest);
}
parent.writeHeapType(curr->castType.getHeapType());
}
parent.writeHeapType(curr->castType.getHeapType());
}

void BinaryInstWriter::visitRefCast(RefCast* curr) {
o << int8_t(BinaryConsts::GCPrefix);
if (curr->type.isNullable()) {
o << U32LEB(BinaryConsts::RefCastNull);
if (curr->type.isExact() &&
parent.getModule()->features.hasCustomDescriptors()) {
// Fall back to the general form with a reftype immediate.
o << U32LEB(BinaryConsts::RefCastRT);
parent.writeType(curr->type);
} else {
o << U32LEB(BinaryConsts::RefCast);
// Use the special-case form with heap type immediate.
if (curr->type.isNullable()) {
o << U32LEB(BinaryConsts::RefCastNull);
} else {
o << U32LEB(BinaryConsts::RefCast);
}
parent.writeHeapType(curr->type.getHeapType());
}
parent.writeHeapType(curr->type.getHeapType());
}

void BinaryInstWriter::visitBrOn(BrOn* curr) {
Expand All @@ -2298,8 +2314,24 @@ void BinaryInstWriter::visitBrOn(BrOn* curr) {
}
assert(curr->ref->type.isRef());
assert(Type::isSubType(curr->castType, curr->ref->type));
uint8_t flags = (curr->ref->type.isNullable() ? 1 : 0) |
(curr->castType.isNullable() ? 2 : 0);
uint8_t flags = 0;
if (curr->ref->type.isNullable()) {
flags |= BinaryConsts::BrOnCastFlag::InputNullable;
}
if (curr->castType.isNullable()) {
flags |= BinaryConsts::BrOnCastFlag::OutputNullable;
}
if (parent.getModule()->features.hasCustomDescriptors()) {
// If custom descriptors (and therefore exact references) are not
// enabled, then these flags wouldn't be recognized, and we will be
// generalizing all exact references to be non-exact anyway.
if (curr->ref->type.isExact()) {
flags |= BinaryConsts::BrOnCastFlag::InputExact;
}
if (curr->castType.isExact()) {
flags |= BinaryConsts::BrOnCastFlag::OutputExact;
}
}
o << flags;
o << U32LEB(getBreakIndex(curr->name));
parent.writeHeapType(curr->ref->type.getHeapType());
Expand Down
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