compiler: save conditional values at data.drop (#724)

Signed-off-by: Takeshi Yoneda <takeshi@tetrate.io>

internal/engine/compiler/impl_amd64.go

@@ -3580,6 +3580,10 @@ func (c *amd64Compiler) compileInitImpl(isTable bool, index, tableIndex uint32)
 
 // compileDataDrop implements compiler.compileDataDrop for the amd64 architecture.
 func (c *amd64Compiler) compileDataDrop(o *wazeroir.OperationDataDrop) error {
+	if err := c.maybeCompileMoveTopConditionalToGeneralPurposeRegister(); err != nil {
+		return err
+	}
+
 	tmp, err := c.allocateRegister(registerTypeGeneralPurpose)
 	if err != nil {
 		return err

internal/engine/compiler/impl_arm64.go

@@ -3221,6 +3221,10 @@ func (c *arm64Compiler) compileInitImpl(isTable bool, index, tableIndex uint32)
 
 // compileDataDrop implements compiler.compileDataDrop for the arm64 architecture.
 func (c *arm64Compiler) compileDataDrop(o *wazeroir.OperationDataDrop) error {
+	if err := c.maybeCompileMoveTopConditionalToGeneralPurposeRegister(); err != nil {
+		return err
+	}
+
 	tmp, err := c.allocateRegister(registerTypeGeneralPurpose)
 	if err != nil {
 		return err

internal/integration_test/fuzzcases/fuzzcases_test.go

@@ -235,3 +235,17 @@ func Test721(t *testing.T) {
 		require.Equal(t, uint64(1), ret[0])
 	})
 }
+
+func Test722(t *testing.T) {
+	run(t, func(t *testing.T, r wazero.Runtime) {
+		mod, err := r.InstantiateModuleFromBinary(ctx, getWasmBinary(t, 722))
+		require.NoError(t, err)
+
+		f := mod.ExportedFunction("conditional before data.drop")
+		require.NotNil(t, f)
+		ret, err := f.Call(ctx)
+		require.NoError(t, err)
+
+		require.Equal(t, uint64(1), ret[0])
+	})
+}

internal/integration_test/fuzzcases/testdata/722.wat

@@ -0,0 +1,10 @@
+(module
+  (func (export "conditional before data.drop") (result i32)
+    ref.null func
+    ref.is_null
+    ;; At this point, i32 value is placed on the conditional register.
+    ;; data.drop must handle it correctly and save it to a general purpose one.
+    data.drop 0
+  )
+  (data "\ff")
+)