[FP16] Implement conversion operations. (#6974)

Note: FP16 is a little different from F32/F64 since it can't represent
the full 2^16 integer range. 65504 is the max whole integer. This leads
to some slightly strange behavior when converting integers greater than
65504 since they become infinity.


Specified at
https://github.com/WebAssembly/half-precision/blob/main/proposals/half-precision/Overview.md

5 files changed, 83 insertions, 0 deletions

diff --git a/src/wasm/literal.cpp b/src/wasm/literal.cpp
index 6aaba729a..b53378cfa 100644
--- a/src/wasm/literal.cpp
+++ b/src/wasm/literal.cpp
@@ -798,6 +798,20 @@ Literal Literal::wrapToI32() const {
   return Literal((int32_t)i64);
 }
 
+Literal Literal::convertSIToF16() const {
+  if (type == Type::i32) {
+    return Literal(fp16_ieee_from_fp32_value(float(i32)));
+  }
+  WASM_UNREACHABLE("invalid type");
+}
+
+Literal Literal::convertUIToF16() const {
+  if (type == Type::i32) {
+    return Literal(fp16_ieee_from_fp32_value(float(uint16_t(i32))));
+  }
+  WASM_UNREACHABLE("invalid type");
+}
+
 Literal Literal::convertSIToF32() const {
   if (type == Type::i32) {
     return Literal(float(i32));
@@ -861,6 +875,14 @@ static Literal saturating_trunc(typename AsInt<F>::type val) {
   return Literal(I(std::trunc(bit_cast<F>(val))));
 }
 
+Literal Literal::truncSatToSI16() const {
+  if (type == Type::f32) {
+    return saturating_trunc<float, int16_t, isInRangeI16TruncS>(
+      Literal(*this).castToI32().geti32());
+  }
+  WASM_UNREACHABLE("invalid type");
+}
+
 Literal Literal::truncSatToSI32() const {
   if (type == Type::f32) {
     return saturating_trunc<float, int32_t, isInRangeI32TruncS>(
@@ -885,6 +907,14 @@ Literal Literal::truncSatToSI64() const {
   WASM_UNREACHABLE("invalid type");
 }
 
+Literal Literal::truncSatToUI16() const {
+  if (type == Type::f32) {
+    return saturating_trunc<float, uint16_t, isInRangeI16TruncU>(
+      Literal(*this).castToI32().geti32());
+  }
+  WASM_UNREACHABLE("invalid type");
+}
+
 Literal Literal::truncSatToUI32() const {
   if (type == Type::f32) {
     return saturating_trunc<float, uint32_t, isInRangeI32TruncU>(
@@ -1997,6 +2027,19 @@ Literal Literal::convertUToF32x4() const {
   return unary<4, &Literal::getLanesI32x4, &Literal::convertUIToF32>(*this);
 }
 
+Literal Literal::truncSatToSI16x8() const {
+  return unary<8, &Literal::getLanesF16x8, &Literal::truncSatToSI16>(*this);
+}
+Literal Literal::truncSatToUI16x8() const {
+  return unary<8, &Literal::getLanesF16x8, &Literal::truncSatToUI16>(*this);
+}
+Literal Literal::convertSToF16x8() const {
+  return unary<8, &Literal::getLanesSI16x8, &Literal::convertSIToF16>(*this);
+}
+Literal Literal::convertUToF16x8() const {
+  return unary<8, &Literal::getLanesSI16x8, &Literal::convertUIToF16>(*this);
+}
+
 Literal Literal::anyTrueV128() const {
   auto lanes = getLanesI32x4();
   for (size_t i = 0; i < 4; ++i) {
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index cb9ea3731..3bb33529b 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -6522,6 +6522,22 @@ bool WasmBinaryReader::maybeVisitSIMDUnary(Expression*& out, uint32_t code) {
       curr = allocator.alloc<Unary>();
       curr->op = RelaxedTruncZeroUVecF64x2ToVecI32x4;
       break;
+    case BinaryConsts::I16x8TruncSatF16x8S:
+      curr = allocator.alloc<Unary>();
+      curr->op = TruncSatSVecF16x8ToVecI16x8;
+      break;
+    case BinaryConsts::I16x8TruncSatF16x8U:
+      curr = allocator.alloc<Unary>();
+      curr->op = TruncSatUVecF16x8ToVecI16x8;
+      break;
+    case BinaryConsts::F16x8ConvertI16x8S:
+      curr = allocator.alloc<Unary>();
+      curr->op = ConvertSVecI16x8ToVecF16x8;
+      break;
+    case BinaryConsts::F16x8ConvertI16x8U:
+      curr = allocator.alloc<Unary>();
+      curr->op = ConvertUVecI16x8ToVecF16x8;
+      break;
     default:
       return false;
   }
diff --git a/src/wasm/wasm-stack.cpp b/src/wasm/wasm-stack.cpp
index a1446c2de..7194229fe 100644
--- a/src/wasm/wasm-stack.cpp
+++ b/src/wasm/wasm-stack.cpp
@@ -1324,6 +1324,22 @@ void BinaryInstWriter::visitUnary(Unary* curr) {
       o << int8_t(BinaryConsts::SIMDPrefix)
         << U32LEB(BinaryConsts::I32x4RelaxedTruncF64x2UZero);
       break;
+    case TruncSatSVecF16x8ToVecI16x8:
+      o << int8_t(BinaryConsts::SIMDPrefix)
+        << U32LEB(BinaryConsts::I16x8TruncSatF16x8S);
+      break;
+    case TruncSatUVecF16x8ToVecI16x8:
+      o << int8_t(BinaryConsts::SIMDPrefix)
+        << U32LEB(BinaryConsts::I16x8TruncSatF16x8U);
+      break;
+    case ConvertSVecI16x8ToVecF16x8:
+      o << int8_t(BinaryConsts::SIMDPrefix)
+        << U32LEB(BinaryConsts::F16x8ConvertI16x8S);
+      break;
+    case ConvertUVecI16x8ToVecF16x8:
+      o << int8_t(BinaryConsts::SIMDPrefix)
+        << U32LEB(BinaryConsts::F16x8ConvertI16x8U);
+      break;
     case InvalidUnary:
       WASM_UNREACHABLE("invalid unary op");
   }
diff --git a/src/wasm/wasm-validator.cpp b/src/wasm/wasm-validator.cpp
index 40726d7cd..a86187fa7 100644
--- a/src/wasm/wasm-validator.cpp
+++ b/src/wasm/wasm-validator.cpp
@@ -2160,6 +2160,10 @@ void FunctionValidator::visitUnary(Unary* curr) {
     case RelaxedTruncUVecF32x4ToVecI32x4:
     case RelaxedTruncZeroSVecF64x2ToVecI32x4:
     case RelaxedTruncZeroUVecF64x2ToVecI32x4:
+    case TruncSatSVecF16x8ToVecI16x8:
+    case TruncSatUVecF16x8ToVecI16x8:
+    case ConvertSVecI16x8ToVecF16x8:
+    case ConvertUVecI16x8ToVecF16x8:
       shouldBeEqual(curr->type, Type(Type::v128), curr, "expected v128 type");
       shouldBeEqual(
         curr->value->type, Type(Type::v128), curr, "expected v128 operand");
diff --git a/src/wasm/wasm.cpp b/src/wasm/wasm.cpp
index 87ae6ac5a..84fd9a06f 100644
--- a/src/wasm/wasm.cpp
+++ b/src/wasm/wasm.cpp
@@ -703,6 +703,10 @@ void Unary::finalize() {
     case RelaxedTruncUVecF32x4ToVecI32x4:
     case RelaxedTruncZeroSVecF64x2ToVecI32x4:
     case RelaxedTruncZeroUVecF64x2ToVecI32x4:
+    case TruncSatSVecF16x8ToVecI16x8:
+    case TruncSatUVecF16x8ToVecI16x8:
+    case ConvertSVecI16x8ToVecF16x8:
+    case ConvertUVecI16x8ToVecF16x8:
       type = Type::v128;
       break;
     case AnyTrueVec128: