compiler: share LLVM function type construction

getFunction and getLLVMFunctionType duplicate the construction of LLVM
result types for functions with zero, one, or multiple results.

Move this code to getLLVMResultType. Also split the existing parameter
expansion code into expandDirectFormalParamType so callers can request
the current flattened parameter types directly.

compiler/calls.go

@@ -102,6 +102,10 @@ func (b *builder) createInvoke(fnType llvm.Type, fn llvm.Value, args []llvm.Valu
 // Expand an argument type to a list that can be used in a function call
 // parameter list.
 func (c *compilerContext) expandFormalParamType(t llvm.Type, name string, goType types.Type) []paramInfo {
+	return c.expandDirectFormalParamType(t, name, goType)
+}
+
+func (c *compilerContext) expandDirectFormalParamType(t llvm.Type, name string, goType types.Type) []paramInfo {
 	switch t.TypeKind() {
 	case llvm.StructTypeKind:
 		fieldInfos := c.flattenAggregateType(t, name, goType)

compiler/func.go

@@ -10,6 +10,21 @@ import (
 	"tinygo.org/x/go-llvm"
 )
 
+func (c *compilerContext) getLLVMResultType(sig *types.Signature) llvm.Type {
+	switch sig.Results().Len() {
+	case 0:
+		return c.ctx.VoidType()
+	case 1:
+		return c.getLLVMType(sig.Results().At(0).Type())
+	default:
+		results := make([]llvm.Type, sig.Results().Len())
+		for i := range results {
+			results[i] = c.getLLVMType(sig.Results().At(i).Type())
+		}
+		return c.ctx.StructType(results, false)
+	}
+}
+
 // createFuncValue creates a function value from a raw function pointer with no
 // context.
 func (b *builder) createFuncValue(funcPtr, context llvm.Value, sig *types.Signature) llvm.Value {
@@ -48,25 +63,7 @@ func (c *compilerContext) getFuncType(typ *types.Signature) llvm.Type {
 
 // getLLVMFunctionType returns a LLVM function type for a given signature.
 func (c *compilerContext) getLLVMFunctionType(typ *types.Signature) llvm.Type {
-	// Get the return type.
-	var returnType llvm.Type
-	switch typ.Results().Len() {
-	case 0:
-		// No return values.
-		returnType = c.ctx.VoidType()
-	case 1:
-		// Just one return value.
-		returnType = c.getLLVMType(typ.Results().At(0).Type())
-	default:
-		// Multiple return values. Put them together in a struct.
-		// This appears to be the common way to handle multiple return values in
-		// LLVM.
-		members := make([]llvm.Type, typ.Results().Len())
-		for i := 0; i < typ.Results().Len(); i++ {
-			members[i] = c.getLLVMType(typ.Results().At(i).Type())
-		}
-		returnType = c.ctx.StructType(members, false)
-	}
+	returnType := c.getLLVMResultType(typ)
 
 	// Get the parameter types.
 	var paramTypes []llvm.Type

compiler/symbol.go

@@ -79,18 +79,7 @@ func (c *compilerContext) getFunction(fn *ssa.Function) (llvm.Type, llvm.Value)
 		return llvmFn.GlobalValueType(), llvmFn
 	}
 
-	var retType llvm.Type
-	if fn.Signature.Results() == nil {
-		retType = c.ctx.VoidType()
-	} else if fn.Signature.Results().Len() == 1 {
-		retType = c.getLLVMType(fn.Signature.Results().At(0).Type())
-	} else {
-		results := make([]llvm.Type, 0, fn.Signature.Results().Len())
-		for v := range fn.Signature.Results().Variables() {
-			results = append(results, c.getLLVMType(v.Type()))
-		}
-		retType = c.ctx.StructType(results, false)
-	}
+	retType := c.getLLVMResultType(fn.Signature)
 
 	var paramInfos []paramInfo
 	for _, param := range getParams(fn.Signature) {