compiler: save conditional values at ref.func (#717)

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

internal/engine/compiler/impl_amd64.go

@@ -4096,6 +4096,10 @@ func (c *amd64Compiler) compileTableFill(o *wazeroir.OperationTableFill) error {
 
 // compileRefFunc implements compiler.compileRefFunc for the amd64 architecture.
 func (c *amd64Compiler) compileRefFunc(o *wazeroir.OperationRefFunc) error {
+	if err := c.maybeCompileMoveTopConditionalToGeneralPurposeRegister(); err != nil {
+		return err
+	}
+
 	ref, err := c.allocateRegister(registerTypeGeneralPurpose)
 	if err != nil {
 		return err

internal/engine/compiler/impl_arm64.go

@@ -3696,6 +3696,10 @@ func (c *arm64Compiler) compileLoadElemInstanceAddress(elemIndex uint32, dst asm
 
 // compileRefFunc implements compiler.compileRefFunc for the arm64 architecture.
 func (c *arm64Compiler) compileRefFunc(o *wazeroir.OperationRefFunc) error {
+	if err := c.maybeCompileMoveTopConditionalToGeneralPurposeRegister(); err != nil {
+		return err
+	}
+
 	ref, err := c.allocateRegister(registerTypeGeneralPurpose)
 	if err != nil {
 		return err

internal/integration_test/fuzzcases/fuzzcases_test.go

@@ -29,6 +29,8 @@ var (
 	case709 []byte
 	//go:embed testdata/715.wasm
 	case715 []byte
+	//go:embed testdata/716.wasm
+	case716 []byte
 )
 
 func runWithCompiler(t *testing.T, runner func(t *testing.T, r wazero.Runtime)) {
@@ -159,3 +161,17 @@ func Test715(t *testing.T) {
 		require.Equal(t, uint64(1), res[0])
 	})
 }
+
+func Test716(t *testing.T) {
+	run(t, func(t *testing.T, r wazero.Runtime) {
+		mod, err := r.InstantiateModuleFromBinary(ctx, case716)
+		require.NoError(t, err)
+
+		f := mod.ExportedFunction("select on ref.func")
+		require.NotNil(t, f)
+		res, err := f.Call(ctx)
+		require.NoError(t, err)
+
+		require.Equal(t, uint64(1), res[0])
+	})
+}

internal/integration_test/fuzzcases/testdata/716.wat

@@ -0,0 +1,14 @@
+(module
+  (func (result i32)
+    i32.const 123
+    ref.null func
+    ref.is_null ;; -> 1
+    ;; At this point, the result of ref.is_null (=1) is on the conditional register.
+    ;; If table.size doesn't save the value into a general purpose register,
+    ;; the result of select below becomes incorrect.
+    ref.func 0
+    ref.is_null ;; -> 0
+    select ;; should select 1
+  )
+  (export "select on ref.func" (func 0))
+)