func (c *compiler) VisitBlockStmt(stmt *ast.BlockStmt, createNewBlock bool) {
// This is a little awkward, but it makes dealing with branching easier.
// A free-standing block statement (i.e. one not attached to a control
// statement) will splice in a new block.
var doneBlock llvm.BasicBlock
if createNewBlock {
currBlock := c.builder.GetInsertBlock()
doneBlock = llvm.InsertBasicBlock(currBlock, "")
doneBlock.MoveAfter(currBlock)
newBlock := llvm.InsertBasicBlock(doneBlock, "")
c.builder.CreateBr(newBlock)
c.builder.SetInsertPointAtEnd(newBlock)
}
for _, stmt := range stmt.List {
c.VisitStmt(stmt)
if _, ok := stmt.(*ast.BranchStmt); ok {
// Ignore anything after a branch statement.
break
}
}
if createNewBlock {
c.maybeImplicitBranch(doneBlock)
c.builder.SetInsertPointAtEnd(doneBlock)
}
}
func (c *compiler) VisitBlockStmt(stmt *ast.BlockStmt, createNewBlock bool) {
// This is a little awkward, but it makes dealing with branching easier.
// A free-standing block statement (i.e. one not attached to a control
// statement) will splice in a new block.
var doneBlock llvm.BasicBlock
if createNewBlock {
currBlock := c.builder.GetInsertBlock()
doneBlock = llvm.InsertBasicBlock(currBlock, "")
doneBlock.MoveAfter(currBlock)
newBlock := llvm.InsertBasicBlock(doneBlock, "")
c.builder.CreateBr(newBlock)
c.builder.SetInsertPointAtEnd(newBlock)
}
// Visit each statement in the block. When we have a terminator,
// ignore everything until we get to a labeled statement.
for _, stmt := range stmt.List {
currBlock := c.builder.GetInsertBlock()
in := currBlock.LastInstruction()
if in.IsNil() || in.IsATerminatorInst().IsNil() {
c.VisitStmt(stmt)
} else if _, ok := stmt.(*ast.LabeledStmt); ok {
// FIXME we might end up with a labeled statement
// with no predecessors, due to dead code elimination.
c.VisitStmt(stmt)
}
}
if createNewBlock {
c.maybeImplicitBranch(doneBlock)
c.builder.SetInsertPointAtEnd(doneBlock)
}
}
// maybeImplicitBranch creates a branch from the current position to the
// specified basic block, if and only if the current basic block's last
// instruction is not a terminator.
//
// If dest is nil, then branch to the next basic block, if any.
func (c *compiler) maybeImplicitBranch(dest llvm.BasicBlock) {
currBlock := c.builder.GetInsertBlock()
if in := currBlock.LastInstruction(); in.IsNil() || in.IsATerminatorInst().IsNil() {
if dest.IsNil() {
dest = llvm.NextBasicBlock(currBlock)
if !dest.IsNil() {
c.builder.CreateBr(dest)
}
} else {
c.builder.CreateBr(dest)
}
}
}
func (c *compiler) VisitIfStmt(stmt *ast.IfStmt) {
curr_block := c.builder.GetInsertBlock()
resume_block := llvm.AddBasicBlock(curr_block.Parent(), "endif")
resume_block.MoveAfter(curr_block)
var if_block, else_block llvm.BasicBlock
if stmt.Else != nil {
else_block = llvm.InsertBasicBlock(resume_block, "else")
if_block = llvm.InsertBasicBlock(else_block, "if")
} else {
if_block = llvm.InsertBasicBlock(resume_block, "if")
}
if stmt.Else == nil {
else_block = resume_block
}
if stmt.Init != nil {
c.PushScope()
c.VisitStmt(stmt.Init)
defer c.PopScope()
}
cond_val := c.VisitExpr(stmt.Cond)
c.builder.CreateCondBr(cond_val.LLVMValue(), if_block, else_block)
c.builder.SetInsertPointAtEnd(if_block)
c.VisitBlockStmt(stmt.Body)
if in := if_block.LastInstruction(); in.IsNil() || in.IsATerminatorInst().IsNil() {
c.builder.CreateBr(resume_block)
}
if stmt.Else != nil {
c.builder.SetInsertPointAtEnd(else_block)
c.VisitStmt(stmt.Else)
if in := else_block.LastInstruction(); in.IsNil() || in.IsATerminatorInst().IsNil() {
c.builder.CreateBr(resume_block)
}
}
// If there's a block after the "resume" block (i.e. a nested control
// statement), then create a branch to it as the last instruction.
c.builder.SetInsertPointAtEnd(resume_block)
if last := resume_block.Parent().LastBasicBlock(); last != resume_block {
c.builder.CreateBr(last)
c.builder.SetInsertPointBefore(resume_block.FirstInstruction())
}
}
// createCall emits the code for a function call, taking into account
// variadic functions, receivers, and panic/defer.
//
// dotdotdot is true if the last argument is followed with "...".
func (c *compiler) createCall(fn *LLVMValue, argValues []Value, dotdotdot, invoke bool) *LLVMValue {
fn_type := fn.Type().Underlying().(*types.Signature)
var args []llvm.Value
// TODO Move all of this to evalCallArgs?
params := fn_type.Params()
if nparams := int(params.Len()); nparams > 0 {
if fn_type.IsVariadic() {
nparams--
}
for i := 0; i < nparams; i++ {
value := argValues[i]
args = append(args, value.LLVMValue())
}
if fn_type.IsVariadic() {
if dotdotdot {
// Calling f(x...). Just pass the slice directly.
slice_value := argValues[nparams].LLVMValue()
args = append(args, slice_value)
} else {
varargs := make([]llvm.Value, len(argValues)-nparams)
for i, value := range argValues[nparams:] {
varargs[i] = value.LLVMValue()
}
param_type := params.At(nparams).Type().(*types.Slice).Elem()
slice_value := c.makeLiteralSlice(varargs, param_type)
args = append(args, slice_value)
}
}
}
var result_type types.Type
switch results := fn_type.Results(); results.Len() {
case 0: // no-op
case 1:
result_type = results.At(0).Type()
default:
result_type = results
}
// Depending on whether the function contains defer statements or not,
// we'll generate either a "call" or an "invoke" instruction.
var createCall = c.builder.CreateCall
if invoke {
f := c.functions.top()
// TODO Create a method on compiler (avoid creating closures).
createCall = func(fn llvm.Value, args []llvm.Value, name string) llvm.Value {
currblock := c.builder.GetInsertBlock()
returnblock := llvm.AddBasicBlock(currblock.Parent(), "")
returnblock.MoveAfter(currblock)
value := c.builder.CreateInvoke(fn, args, returnblock, f.unwindblock, "")
c.builder.SetInsertPointAtEnd(returnblock)
return value
}
}
var fnptr llvm.Value
fnval := fn.LLVMValue()
if fnval.Type().TypeKind() == llvm.PointerTypeKind {
fnptr = fnval
} else {
fnptr = c.builder.CreateExtractValue(fnval, 0, "")
context := c.builder.CreateExtractValue(fnval, 1, "")
fntyp := fnptr.Type().ElementType()
paramTypes := fntyp.ParamTypes()
// If the context is not a constant null, and we're not
// dealing with a method (where we don't care about the value
// of the receiver), then we must conditionally call the
// function with the additional receiver/closure.
if !context.IsNull() || fn_type.Recv() != nil {
// Store the blocks for referencing in the Phi below;
// note that we update the block after each createCall,
// since createCall may create new blocks and we want
// the predecessors to the Phi.
var nullctxblock llvm.BasicBlock
var nonnullctxblock llvm.BasicBlock
var endblock llvm.BasicBlock
var nullctxresult llvm.Value
// len(paramTypes) == len(args) iff function is not a method.
if !context.IsConstant() && len(paramTypes) == len(args) {
currblock := c.builder.GetInsertBlock()
endblock = llvm.AddBasicBlock(currblock.Parent(), "")
endblock.MoveAfter(currblock)
nonnullctxblock = llvm.InsertBasicBlock(endblock, "")
nullctxblock = llvm.InsertBasicBlock(nonnullctxblock, "")
nullctx := c.builder.CreateIsNull(context, "")
c.builder.CreateCondBr(nullctx, nullctxblock, nonnullctxblock)
// null context case.
c.builder.SetInsertPointAtEnd(nullctxblock)
nullctxresult = createCall(fnptr, args, "")
nullctxblock = c.builder.GetInsertBlock()
c.builder.CreateBr(endblock)
c.builder.SetInsertPointAtEnd(nonnullctxblock)
}
// non-null context case.
var result llvm.Value
args := append([]llvm.Value{context}, args...)
if len(paramTypes) < len(args) {
returnType := fntyp.ReturnType()
ctxType := context.Type()
paramTypes := append([]llvm.Type{ctxType}, paramTypes...)
vararg := fntyp.IsFunctionVarArg()
fntyp := llvm.FunctionType(returnType, paramTypes, vararg)
fnptrtyp := llvm.PointerType(fntyp, 0)
fnptr = c.builder.CreateBitCast(fnptr, fnptrtyp, "")
}
result = createCall(fnptr, args, "")
// If the return type is not void, create a
// PHI node to select which value to return.
if !nullctxresult.IsNil() {
nonnullctxblock = c.builder.GetInsertBlock()
c.builder.CreateBr(endblock)
c.builder.SetInsertPointAtEnd(endblock)
if result.Type().TypeKind() != llvm.VoidTypeKind {
phiresult := c.builder.CreatePHI(result.Type(), "")
values := []llvm.Value{nullctxresult, result}
blocks := []llvm.BasicBlock{nullctxblock, nonnullctxblock}
phiresult.AddIncoming(values, blocks)
result = phiresult
}
}
return c.NewValue(result, result_type)
}
}
result := createCall(fnptr, args, "")
return c.NewValue(result, result_type)
}