Implement f32.demote_f64

wasmx · Aug 12, 2020 · 0fa4519 · 0fa4519
1 parent a1f001d
commit 0fa4519
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Showing 2 changed files with 64 additions and 2 deletions.
diff --git a/lib/fizzy/execute.cpp b/lib/fizzy/execute.cpp
@@ -510,6 +510,12 @@ inline uint64_t popcnt64(uint64_t value) noexcept
     return static_cast<uint64_t>(__builtin_popcountll(value));
 }
 
+__attribute__((no_sanitize("float-cast-overflow"))) inline constexpr float demote(
+    double value) noexcept
+{
+    return static_cast<float>(value);
+}
+
 std::optional<uint32_t> find_export(const Module& module, ExternalKind kind, std::string_view name)
 {
     const auto it = std::find_if(module.exportsec.begin(), module.exportsec.end(),
@@ -1655,6 +1661,11 @@ ExecutionResult execute(Instance& instance, FuncIdx func_idx, span<const Value>
             convert<uint64_t, float>(stack);
             break;
         }
+        case Instr::f32_demote_f64:
+        {
+            stack.top() = demote(stack.top().f64);
+            break;
+        }
         case Instr::f64_convert_i32_s:
         {
             convert<int32_t, double>(stack);
@@ -1705,7 +1716,6 @@ ExecutionResult execute(Instance& instance, FuncIdx func_idx, span<const Value>
         case Instr::f64_min:
         case Instr::f64_max:
         case Instr::f64_copysign:
-        case Instr::f32_demote_f64:
         case Instr::i32_reinterpret_f32:
         case Instr::i64_reinterpret_f64:
         case Instr::f32_reinterpret_i32:

diff --git a/test/unittests/execute_floating_point_test.cpp b/test/unittests/execute_floating_point_test.cpp
@@ -415,7 +415,7 @@ TEST(execute_floating_point, f64_promote_f32)
       f64.promote_f32
     )
     */
-    auto wasm = from_hex("0061736d0100000001060160017d017c030201000a070105002000bb0b");
+    const auto wasm = from_hex("0061736d0100000001060160017d017c030201000a070105002000bb0b");
     auto instance = instantiate(parse(wasm));
 
     const std::pair<float, double> test_cases[] = {
@@ -465,6 +465,58 @@ TEST(execute_floating_point, f64_promote_f32)
     EXPECT_GT(FP{res4.value.f64}.nan_payload(), FP64::canon);
 }
 
+TEST(execute_floating_point, f32_demote_f64)
+{
+    /* wat2wasm
+    (func (param f64) (result f32)
+      local.get 0
+      f32.demote_f64
+    )
+    */
+    const auto wasm = from_hex("0061736d0100000001060160017c017d030201000a070105002000b60b");
+    auto instance = instantiate(parse(wasm));
+
+    const std::pair<double, float> test_cases[] = {
+        {0.0, 0.0f},
+        {-0.0, -0.0f},
+        {1.0, 1.0f},
+        {-1.0, -1.0f},
+        {double{FP32::Limits::lowest()}, FP32::Limits::lowest()},
+        {double{FP32::Limits::max()}, FP32::Limits::max()},
+        {double{FP32::Limits::min()}, FP32::Limits::min()},
+        {double{FP32::Limits::denorm_min()}, FP32::Limits::denorm_min()},
+
+        // Out of range values rounded to max/lowest.
+        {std::nextafter(double{FP32::Limits::max()}, FP64::Limits::infinity()),
+            FP32::Limits::max()},
+        {std::nextafter(double{FP32::Limits::lowest()}, -FP64::Limits::infinity()),
+            FP32::Limits::lowest()},
+        {double{FP32::Limits::max()} * 0x1.0000008000007p0, FP32::Limits::max()},
+        {double{FP32::Limits::lowest()} * 0x1.0000008000007p0, FP32::Limits::lowest()},
+
+        // The smallest of range values rounded to infinity.
+        {double{FP32::Limits::max()} * 0x1.0000008000008p0, FP32::Limits::infinity()},
+        {double{FP32::Limits::lowest()} * 0x1.0000008000008p0, -FP32::Limits::infinity()},
+
+        {FP64::Limits::infinity(), FP32::Limits::infinity()},
+        {-FP64::Limits::infinity(), -FP32::Limits::infinity()},
+
+        // The canonical NaN must result in canonical NaN (only the top bit set).
+        {FP32::nan(FP32::canon), FP64::nan(FP64::canon)},
+        {-FP32::nan(FP32::canon), -FP64::nan(FP64::canon)},
+    };
+
+    for (const auto& [arg, expected] : test_cases)
+    {
+        EXPECT_THAT(execute(*instance, 0, {arg}), Result(expected)) << arg << " -> " << expected;
+    }
+
+    EXPECT_THAT(execute(*instance, 0, {FP64::nan(FP64::canon + 1)}), ArithmeticNaN(float{}));
+    EXPECT_THAT(execute(*instance, 0, {-FP64::nan(FP64::canon + 1)}), ArithmeticNaN(float{}));
+    EXPECT_THAT(execute(*instance, 0, {FP64::nan(1)}), ArithmeticNaN(float{}));
+    EXPECT_THAT(execute(*instance, 0, {-FP64::nan(1)}), ArithmeticNaN(float{}));
+}
+
 
 template <typename SrcT, typename DstT>
 struct ConversionPairWasmTraits;