compiler: small cleanup in call handling code

compiler/calls.go

@@ -1,10 +1,7 @@
 package compiler
 
 import (
-	"go/types"
-
 	"github.com/aykevl/llvm/bindings/go/llvm"
-	"github.com/aykevl/tinygo/ir"
 	"golang.org/x/tools/go/ssa"
 )
 
@@ -21,13 +18,16 @@ import (
 //     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
 //     the work of LLVM optimizers easier.
-//   * Closures have an extra paramter appended at the end of the argument list,
-//     which is a pointer to a struct containing free variables.
+//   * Closures have an extra context paramter appended at the end of the
+//     argument list.
 //   * Blocking functions have a coroutine pointer prepended to the argument
 //     list, see src/runtime/scheduler.go for details.
 
+// The maximum number of arguments that can be expanded from a single struct. If
+// a struct contains more fields, it is passed as value.
 const MaxFieldsPerParam = 3
 
+// Shortcut: create a call to runtime.<fnName> with the given arguments.
 func (c *Compiler) createRuntimeCall(fnName string, args []llvm.Value, name string) llvm.Value {
 	runtimePkg := c.ir.Program.ImportedPackage("runtime")
 	member := runtimePkg.Members[fnName]
@@ -35,14 +35,11 @@ func (c *Compiler) createRuntimeCall(fnName string, args []llvm.Value, name stri
 		panic("trying to call runtime." + fnName)
 	}
 	fn := c.ir.GetFunction(member.(*ssa.Function))
-	return c.createCall(fn, args, name)
+	return c.createCall(fn.LLVMFn, args, name)
 }
 
-func (c *Compiler) createCall(fn *ir.Function, args []llvm.Value, name string) llvm.Value {
-	return c.createIndirectCall(fn.Signature, fn.LLVMFn, args, name)
-}
-
-func (c *Compiler) createIndirectCall(sig *types.Signature, fn llvm.Value, args []llvm.Value, name string) llvm.Value {
+// Create a call to the given function with the arguments possibly expanded.
+func (c *Compiler) createCall(fn llvm.Value, args []llvm.Value, name string) llvm.Value {
 	expanded := make([]llvm.Value, 0, len(args))
 	for _, arg := range args {
 		fragments := c.expandFormalParam(arg)
@@ -51,14 +48,8 @@ func (c *Compiler) createIndirectCall(sig *types.Signature, fn llvm.Value, args
 	return c.builder.CreateCall(fn, expanded, name)
 }
 
-func (c *Compiler) getLLVMParamTypes(t types.Type) ([]llvm.Type, error) {
-	llvmType, err := c.getLLVMType(t)
-	if err != nil {
-		return nil, err
-	}
-	return c.expandFormalParamType(llvmType), nil
-}
-
+// Expand an argument type to a list that can be used in a function call
+// paramter list.
 func (c *Compiler) expandFormalParamType(t llvm.Type) []llvm.Type {
 	switch t.TypeKind() {
 	case llvm.StructTypeKind:
@@ -75,7 +66,7 @@ func (c *Compiler) expandFormalParamType(t llvm.Type) []llvm.Type {
 	}
 }
 
-// Convert an argument to one that can be passed in a parameter.
+// Equivalent of expandFormalParamType for parameter values.
 func (c *Compiler) expandFormalParam(v llvm.Value) []llvm.Value {
 	switch v.Type().TypeKind() {
 	case llvm.StructTypeKind:
@@ -96,6 +87,8 @@ func (c *Compiler) expandFormalParam(v llvm.Value) []llvm.Value {
 	}
 }
 
+// Try to flatten a struct type to a list of types. Returns a 1-element slice
+// with the passed in type if this is not possible.
 func (c *Compiler) flattenAggregateType(t llvm.Type) []llvm.Type {
 	switch t.TypeKind() {
 	case llvm.StructTypeKind:
@@ -110,7 +103,8 @@ func (c *Compiler) flattenAggregateType(t llvm.Type) []llvm.Type {
 	}
 }
 
-// Break down a struct into its elementary types for argument passing.
+// Break down a struct into its elementary types for argument passing. The value
+// equivalent of flattenAggregateType
 func (c *Compiler) flattenAggregate(v llvm.Value) []llvm.Value {
 	switch v.Type().TypeKind() {
 	case llvm.StructTypeKind:
@@ -126,6 +120,7 @@ func (c *Compiler) flattenAggregate(v llvm.Value) []llvm.Value {
 	}
 }
 
+// Collapse a list of fields into its original value.
 func (c *Compiler) collapseFormalParam(t llvm.Type, fields []llvm.Value) llvm.Value {
 	param, remaining := c.collapseFormalParamInternal(t, fields)
 	if len(remaining) != 0 {
@@ -134,7 +129,7 @@ func (c *Compiler) collapseFormalParam(t llvm.Type, fields []llvm.Value) llvm.Va
 	return param
 }
 
-// Returns (value, remainingFields).
+// Returns (value, remainingFields). Used by collapseFormalParam.
 func (c *Compiler) collapseFormalParamInternal(t llvm.Type, fields []llvm.Value) (llvm.Value, []llvm.Value) {
 	switch t.TypeKind() {
 	case llvm.StructTypeKind: