From a21ebae6521b2310b18a3a777575d9f479133f02 Mon Sep 17 00:00:00 2001
From: Ali Mohammad Pur <ali.mpfard@gmail.com>
Date: Tue, 18 May 2021 01:19:40 +0430
Subject: [PATCH] LibWasm: Implement checked truncation instructions

This implements the 8 i<n>.truncate.f<n>_<s> instructions.
---
 .../LibWasm/AbstractMachine/AbstractMachine.h |  2 +
 .../LibWasm/AbstractMachine/Interpreter.cpp   | 87 ++++++++++++++++---
 .../LibWasm/AbstractMachine/Interpreter.h     |  7 ++
 3 files changed, 86 insertions(+), 10 deletions(-)

diff --git a/Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.h b/Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.h
index 42646df276..315d6cee8d 100644
--- a/Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.h
+++ b/Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.h
@@ -115,6 +115,8 @@ public:
             [&](auto value) {
                 if constexpr (IsSame<T, decltype(value)>)
                     result = value;
+                else if constexpr (!IsFloatingPoint<T> && IsSame<decltype(value), MakeSigned<T>>)
+                    result = value;
             },
             [&](const FunctionAddress& address) {
                 if constexpr (IsSame<T, FunctionAddress>)
diff --git a/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp b/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp
index 6e789c8671..68312a5f3c 100644
--- a/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp
+++ b/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp
@@ -274,6 +274,51 @@ struct ConvertToRaw<double> {
     }
 };
 
+template<typename V, typename T>
+MakeSigned<T> Interpreter::checked_signed_truncate(V value)
+{
+    if (isnan(value) || isinf(value)) { // "undefined", let's just trap.
+        m_do_trap = true;
+        return 0;
+    }
+
+    double truncated;
+    if constexpr (IsSame<float, V>)
+        truncated = truncf(value);
+    else
+        truncated = trunc(value);
+
+    using SignedT = MakeSigned<T>;
+    if (NumericLimits<SignedT>::min() <= truncated && static_cast<double>(NumericLimits<SignedT>::max()) >= truncated)
+        return static_cast<SignedT>(truncated);
+
+    dbgln_if(WASM_TRACE_DEBUG, "Truncate out of range error");
+    m_do_trap = true;
+    return true;
+}
+
+template<typename V, typename T>
+MakeUnsigned<T> Interpreter::checked_unsigned_truncate(V value)
+{
+    if (isnan(value) || isinf(value)) { // "undefined", let's just trap.
+        m_do_trap = true;
+        return 0;
+    }
+    double truncated;
+    if constexpr (IsSame<float, V>)
+        truncated = truncf(value);
+    else
+        truncated = trunc(value);
+
+    using UnsignedT = MakeUnsigned<T>;
+    if (NumericLimits<UnsignedT>::min() <= truncated && static_cast<double>(NumericLimits<UnsignedT>::max()) >= truncated)
+        return static_cast<UnsignedT>(truncated);
+
+    dbgln_if(WASM_TRACE_DEBUG, "Truncate out of range error");
+    m_do_trap = true;
+    return true;
+}
+
 Vector<NonnullOwnPtr<Value>> Interpreter::pop_values(Configuration& configuration, size_t count)
 {
     Vector<NonnullOwnPtr<Value>> results;
@@ -753,20 +798,42 @@ void Interpreter::interpret(Configuration& configuration, InstructionPointer& ip
         BINARY_PREFIX_NUMERIC_OPERATION(double, copysign, double);
     case Instructions::i32_wrap_i64.value():
         UNARY_MAP(i64, i32, i32);
-    case Instructions::i32_trunc_sf32.value():
-    case Instructions::i32_trunc_uf32.value():
-    case Instructions::i32_trunc_sf64.value():
-    case Instructions::i32_trunc_uf64.value():
-        goto unimplemented;
+    case Instructions::i32_trunc_sf32.value(): {
+        auto fn = [this](auto& v) { return checked_signed_truncate<float, i32>(v); };
+        UNARY_MAP(float, fn, i32);
+    }
+    case Instructions::i32_trunc_uf32.value(): {
+        auto fn = [this](auto& value) { return checked_unsigned_truncate<float, i32>(value); };
+        UNARY_MAP(float, fn, i32);
+    }
+    case Instructions::i32_trunc_sf64.value(): {
+        auto fn = [this](auto& value) { return checked_signed_truncate<double, i32>(value); };
+        UNARY_MAP(double, fn, i32);
+    }
+    case Instructions::i32_trunc_uf64.value(): {
+        auto fn = [this](auto& value) { return checked_unsigned_truncate<double, i32>(value); };
+        UNARY_MAP(double, fn, i32);
+    }
+    case Instructions::i64_trunc_sf32.value(): {
+        auto fn = [this](auto& value) { return checked_signed_truncate<float, i64>(value); };
+        UNARY_MAP(float, fn, i64);
+    }
+    case Instructions::i64_trunc_uf32.value(): {
+        auto fn = [this](auto& value) { return checked_unsigned_truncate<float, i64>(value); };
+        UNARY_MAP(float, fn, i64);
+    }
+    case Instructions::i64_trunc_sf64.value(): {
+        auto fn = [this](auto& value) { return checked_signed_truncate<double, i64>(value); };
+        UNARY_MAP(double, fn, i64);
+    }
+    case Instructions::i64_trunc_uf64.value(): {
+        auto fn = [this](auto& value) { return checked_unsigned_truncate<double, i64>(value); };
+        UNARY_MAP(double, fn, i64);
+    }
     case Instructions::i64_extend_si32.value():
         UNARY_MAP(i32, i64, i64);
     case Instructions::i64_extend_ui32.value():
         UNARY_MAP(u32, i64, i64);
-    case Instructions::i64_trunc_sf32.value():
-    case Instructions::i64_trunc_uf32.value():
-    case Instructions::i64_trunc_sf64.value():
-    case Instructions::i64_trunc_uf64.value():
-        goto unimplemented;
     case Instructions::f32_convert_si32.value():
         UNARY_MAP(i32, float, float);
     case Instructions::f32_convert_ui32.value():
diff --git a/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.h b/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.h
index e78f8f462d..0e06650bf5 100644
--- a/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.h
+++ b/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.h
@@ -20,6 +20,13 @@ private:
     ReadonlyBytes load_from_memory(Configuration&, const Instruction&, size_t);
     void store_to_memory(Configuration&, const Instruction&, ReadonlyBytes data);
     void call_address(Configuration&, FunctionAddress);
+
+    template<typename V, typename T>
+    MakeUnsigned<T> checked_unsigned_truncate(V);
+
+    template<typename V, typename T>
+    MakeSigned<T> checked_signed_truncate(V);
+
     Vector<NonnullOwnPtr<Value>> pop_values(Configuration& configuration, size_t count);
     bool trap_if_not(bool value)
     {