compiler: fix expanding zero-length structs

compiler/calls.go

@@ -14,6 +14,7 @@ import (
 //       {i8*, i32}         -> i8*, i32
 //       {{i8*, i32}, i16}  -> i8*, i32, i16
 //       {{i64}}            -> i64
+//       {}                 ->
 //       {i8*, i32, i8, i8} -> {i8*, i32, i8, i8}
 //     Note that all native Go data types that don't exist in LLVM (string,
 //     slice, interface, fat function pointer) can be expanded this way, making
@@ -92,8 +93,8 @@ func (c *Compiler) expandFormalParam(v llvm.Value) []llvm.Value {
 func (c *Compiler) flattenAggregateType(t llvm.Type) []llvm.Type {
 	switch t.TypeKind() {
 	case llvm.StructTypeKind:
-		fields := make([]llvm.Type, 0, len(t.Subtypes()))
-		for _, subfield := range t.Subtypes() {
+		fields := make([]llvm.Type, 0, t.StructElementTypesCount())
+		for _, subfield := range t.StructElementTypes() {
 			subfields := c.flattenAggregateType(subfield)
 			fields = append(fields, subfields...)
 		}
@@ -108,8 +109,8 @@ func (c *Compiler) flattenAggregateType(t llvm.Type) []llvm.Type {
 func (c *Compiler) flattenAggregate(v llvm.Value) []llvm.Value {
 	switch v.Type().TypeKind() {
 	case llvm.StructTypeKind:
-		fields := make([]llvm.Value, 0, len(v.Type().Subtypes()))
-		for i := range v.Type().Subtypes() {
+		fields := make([]llvm.Value, 0, v.Type().StructElementTypesCount())
+		for i := range v.Type().StructElementTypes() {
 			subfield := c.builder.CreateExtractValue(v, i, "")
 			subfields := c.flattenAggregate(subfield)
 			fields = append(fields, subfields...)
@@ -138,7 +139,7 @@ func (c *Compiler) collapseFormalParamInternal(t llvm.Type, fields []llvm.Value)
 			if err != nil {
 				panic("could not get zero value of struct: " + err.Error())
 			}
-			for i, subtyp := range t.Subtypes() {
+			for i, subtyp := range t.StructElementTypes() {
 				structField, remaining := c.collapseFormalParamInternal(subtyp, fields)
 				fields = remaining
 				value = c.builder.CreateInsertValue(value, structField, i, "")

testdata/structexpand.go

@@ -0,0 +1,104 @@
+package main
+
+// TODO: add .ll test files to check the output
+
+type s0 struct {
+}
+
+type s1 struct {
+	a byte
+}
+
+type s2 struct {
+	a byte
+	b byte
+}
+
+type s3 struct {
+	a byte
+	b byte
+	c byte
+}
+
+// should not be expanded
+type s4 struct {
+	a byte
+	b byte
+	c byte
+	d byte
+}
+
+type s5 struct {
+	a struct {
+		aa byte
+		ab byte
+	}
+	b byte
+}
+
+type s6 struct {
+	a string
+	b byte
+}
+
+type s7 struct {
+	a interface{}
+	b byte
+}
+
+// should not be expanded
+type s8 struct {
+	a []byte // 3 elements
+	b byte   // 1 element
+}
+
+type s9 struct {
+}
+
+func test1(s s1) {
+	println("test1")
+}
+
+func test2(s s2) {
+	println("test2")
+}
+
+func test3(s s3) {
+	println("test3")
+}
+
+func test4(s s4) {
+	println("test4")
+}
+
+func test5(s s5) {
+	println("test5")
+}
+
+func test6(s s6) {
+	println("test6")
+}
+
+func test7(s s7) {
+	println("test7")
+}
+
+func test8(s s8) {
+	println("test8")
+}
+
+func test9(s s9) {
+	println("test9")
+}
+
+func main() {
+	test1(s1{})
+	test2(s2{})
+	test3(s3{})
+	test4(s4{})
+	test5(s5{})
+	test6(s6{})
+	test7(s7{})
+	test8(s8{})
+	test9(s9{})
+}

testdata/structexpand.txt

@@ -0,0 +1,9 @@
+test1
+test2
+test3
+test4
+test5
+test6
+test7
+test8
+test9