func (v *Codegen) genIfStat(n *parser.IfStat) {
// Warning to all who tread here:
// This function is complicated, but theoretically it should never need to
// be changed again. God help the soul who has to edit this.
if !v.inFunction() {
panic("tried to gen if stat not in function")
}
statTerm := semantic.IsNodeTerminating(n)
var end llvm.BasicBlock
if !statTerm {
end = llvm.AddBasicBlock(v.currentLLVMFunction(), "end")
}
for i, expr := range n.Exprs {
cond := v.genExpr(expr)
ifTrue := llvm.AddBasicBlock(v.currentLLVMFunction(), "if_true")
ifFalse := llvm.AddBasicBlock(v.currentLLVMFunction(), "if_false")
v.builder().CreateCondBr(cond, ifTrue, ifFalse)
v.builder().SetInsertPointAtEnd(ifTrue)
v.genBlock(n.Bodies[i])
if !statTerm && !n.Bodies[i].IsTerminating && !isBreakOrNext(n.Bodies[i].LastNode()) {
v.builder().CreateBr(end)
}
v.builder().SetInsertPointAtEnd(ifFalse)
if !statTerm {
end.MoveAfter(ifFalse)
}
}
if n.Else != nil {
v.genBlock(n.Else)
}
if !statTerm && (n.Else == nil || (!n.Else.IsTerminating && !isBreakOrNext(n.Else.LastNode()))) {
v.builder().CreateBr(end)
}
if !statTerm {
v.builder().SetInsertPointAtEnd(end)
}
}
func (c *Codegen) generateControl(node *parser.IfStmtNode) (ret bool) {
currFunc := c.module.NamedFunction(c.currFunc)
tru := llvm.AddBasicBlock(currFunc, "")
var els llvm.BasicBlock
if node.Else != nil {
els = llvm.AddBasicBlock(currFunc, "")
}
exit := llvm.AddBasicBlock(currFunc, "")
cond := c.generateExpression(node.Condition)
if node.Else != nil {
c.builder.CreateCondBr(cond, tru, els)
} else {
c.builder.CreateCondBr(cond, tru, exit)
}
c.builder.SetInsertPoint(tru, tru.LastInstruction())
if c.generateBlock(node.Body) {
ret = true
} else {
c.builder.CreateBr(exit)
}
if node.Else != nil {
c.builder.SetInsertPoint(els, els.LastInstruction())
var ok bool
switch t := node.Else.(type) {
case *parser.BlockNode:
ok = c.generateBlock(t)
ret = ok && ret
case *parser.IfStmtNode:
ok = c.generateControl(t)
ret = ok && ret
}
if !ok {
c.builder.CreateBr(exit)
}
}
c.builder.SetInsertPoint(exit, exit.LastInstruction())
return
}
// parseBasicBlock converts the provided LLVM IR basic block into a basic block
// in which the instructions have been translated to Go AST statement nodes but
// the terminator instruction is an unmodified LLVM IR value.
func parseBasicBlock(llBB llvm.BasicBlock) (bb *basicBlock, err error) {
name, err := getBBName(llBB.AsValue())
if err != nil {
return nil, err
}
bb = &basicBlock{name: name, phis: make(map[string][]*definition)}
for inst := llBB.FirstInstruction(); !inst.IsNil(); inst = llvm.NextInstruction(inst) {
// Handle terminator instruction.
if inst == llBB.LastInstruction() {
err = bb.addTerm(inst)
if err != nil {
return nil, errutil.Err(err)
}
return bb, nil
}
// Handle PHI instructions.
if inst.InstructionOpcode() == llvm.PHI {
ident, def, err := parsePHIInst(inst)
if err != nil {
return nil, errutil.Err(err)
}
bb.phis[ident] = def
continue
}
// Handle non-terminator instructions.
stmt, err := parseInst(inst)
if err != nil {
return nil, err
}
bb.stmts = append(bb.stmts, stmt)
}
return nil, errutil.Newf("invalid basic block %q; contains no instructions", name)
}
func (u *unit) defineFunction(f *ssa.Function) {
// Only define functions from this package, or synthetic
// wrappers (which do not have a package).
if f.Pkg != nil && f.Pkg != u.pkg {
return
}
llfn := u.resolveFunctionGlobal(f)
linkage := u.getFunctionLinkage(f)
isMethod := f.Signature.Recv() != nil
// Methods cannot be referred to via a descriptor.
if !isMethod {
llfd := u.resolveFunctionDescriptorGlobal(f)
llfd.SetInitializer(llvm.ConstBitCast(llfn, llvm.PointerType(llvm.Int8Type(), 0)))
llfd.SetLinkage(linkage)
}
// We only need to emit a descriptor for functions without bodies.
if len(f.Blocks) == 0 {
return
}
ssaopt.LowerAllocsToStack(f)
if u.DumpSSA {
f.WriteTo(os.Stderr)
}
fr := newFrame(u, llfn)
defer fr.dispose()
fr.addCommonFunctionAttrs(fr.function)
fr.function.SetLinkage(linkage)
fr.logf("Define function: %s", f.String())
fti := u.llvmtypes.getSignatureInfo(f.Signature)
delete(u.undefinedFuncs, f)
fr.retInf = fti.retInf
// Push the compile unit and function onto the debug context.
if u.GenerateDebug {
u.debug.PushFunction(fr.function, f.Signature, f.Pos())
defer u.debug.PopFunction()
u.debug.SetLocation(fr.builder, f.Pos())
}
// If a function calls recover, we create a separate function to
// hold the real function, and this function calls __go_can_recover
// and bridges to it.
if callsRecover(f) {
fr = fr.bridgeRecoverFunc(fr.function, fti)
}
fr.blocks = make([]llvm.BasicBlock, len(f.Blocks))
fr.lastBlocks = make([]llvm.BasicBlock, len(f.Blocks))
for i, block := range f.Blocks {
fr.blocks[i] = llvm.AddBasicBlock(fr.function, fmt.Sprintf(".%d.%s", i, block.Comment))
}
fr.builder.SetInsertPointAtEnd(fr.blocks[0])
fr.transformSwitches(f)
prologueBlock := llvm.InsertBasicBlock(fr.blocks[0], "prologue")
fr.builder.SetInsertPointAtEnd(prologueBlock)
for i, param := range f.Params {
llparam := fti.argInfos[i].decode(llvm.GlobalContext(), fr.builder, fr.builder)
if isMethod && i == 0 {
if _, ok := param.Type().Underlying().(*types.Pointer); !ok {
llparam = fr.builder.CreateBitCast(llparam, llvm.PointerType(fr.types.ToLLVM(param.Type()), 0), "")
llparam = fr.builder.CreateLoad(llparam, "")
}
}
fr.env[param] = newValue(llparam, param.Type())
}
// Load closure, extract free vars.
if len(f.FreeVars) > 0 {
for _, fv := range f.FreeVars {
fr.env[fv] = newValue(llvm.ConstNull(u.llvmtypes.ToLLVM(fv.Type())), fv.Type())
}
elemTypes := make([]llvm.Type, len(f.FreeVars)+1)
elemTypes[0] = llvm.PointerType(llvm.Int8Type(), 0) // function pointer
for i, fv := range f.FreeVars {
elemTypes[i+1] = u.llvmtypes.ToLLVM(fv.Type())
}
structType := llvm.StructType(elemTypes, false)
closure := fr.function.Param(fti.chainIndex)
closure = fr.builder.CreateBitCast(closure, llvm.PointerType(structType, 0), "")
for i, fv := range f.FreeVars {
ptr := fr.builder.CreateStructGEP(closure, i+1, "")
ptr = fr.builder.CreateLoad(ptr, "")
fr.env[fv] = newValue(ptr, fv.Type())
}
}
// Allocate stack space for locals in the prologue block.
for _, local := range f.Locals {
typ := fr.llvmtypes.ToLLVM(deref(local.Type()))
alloca := fr.builder.CreateAlloca(typ, local.Comment)
fr.memsetZero(alloca, llvm.SizeOf(typ))
bcalloca := fr.builder.CreateBitCast(alloca, llvm.PointerType(llvm.Int8Type(), 0), "")
value := newValue(bcalloca, local.Type())
fr.env[local] = value
}
// If the function contains any defers, we must first create
// an unwind block. We can short-circuit the check for defers with
// f.Recover != nil.
if f.Recover != nil || hasDefer(f) {
fr.unwindBlock = llvm.AddBasicBlock(fr.function, "")
fr.frameptr = fr.builder.CreateAlloca(llvm.Int8Type(), "")
}
// Keep track of the block into which we need to insert the call
// to __go_register_gc_roots. This needs to be inserted after the
// init guard check under the llgo ABI.
var registerGcBlock llvm.BasicBlock
// If this is the "init" function, emit the init guard check and
// enable init-specific optimizations.
if !isMethod && f.Name() == "init" {
registerGcBlock = fr.emitInitPrologue()
fr.isInit = true
}
fr.builder.CreateBr(fr.blocks[0])
fr.allocaBuilder.SetInsertPointBefore(prologueBlock.FirstInstruction())
for _, block := range f.DomPreorder() {
llblock := fr.blocks[block.Index]
if llblock.IsNil() {
continue
}
fr.translateBlock(block, llblock)
}
fr.fixupPhis()
if !fr.unwindBlock.IsNil() {
fr.setupUnwindBlock(f.Recover, f.Signature.Results())
}
// The init function needs to register the GC roots first. We do this
// after generating code for it because allocations may have caused
// additional GC roots to be created.
if fr.isInit {
fr.builder.SetInsertPointBefore(registerGcBlock.FirstInstruction())
fr.registerGcRoots()
}
}
