d8cc48b09b
This package was long making the design of the compiler more complicated than it needs to be. Previously this package implemented several optimization passes, but those passes have since moved to work directly with LLVM IR instead of Go SSA. The only remaining pass is the SimpleDCE pass. This commit removes the *ir.Function type that permeated the whole compiler and instead switches to use *ssa.Function directly. The SimpleDCE pass is kept but is far less tightly coupled to the rest of the compiler so that it can easily be removed once the switch to building and caching packages individually happens.
455 строки
16 КиБ
Go
455 строки
16 КиБ
Go
package compiler
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// This file implements the 'defer' keyword in Go.
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// Defer statements are implemented by transforming the function in the
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// following way:
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// * Creating an alloca in the entry block that contains a pointer (initially
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// null) to the linked list of defer frames.
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// * Every time a defer statement is executed, a new defer frame is created
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// using alloca with a pointer to the previous defer frame, and the head
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// pointer in the entry block is replaced with a pointer to this defer
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// frame.
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// * On return, runtime.rundefers is called which calls all deferred functions
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// from the head of the linked list until it has gone through all defer
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// frames.
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import (
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"go/types"
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"github.com/tinygo-org/tinygo/compiler/llvmutil"
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"golang.org/x/tools/go/ssa"
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"tinygo.org/x/go-llvm"
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)
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// deferInitFunc sets up this function for future deferred calls. It must be
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// called from within the entry block when this function contains deferred
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// calls.
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func (b *builder) deferInitFunc() {
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// Some setup.
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b.deferFuncs = make(map[*ssa.Function]int)
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b.deferInvokeFuncs = make(map[string]int)
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b.deferClosureFuncs = make(map[*ssa.Function]int)
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b.deferExprFuncs = make(map[ssa.Value]int)
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b.deferBuiltinFuncs = make(map[ssa.Value]deferBuiltin)
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// Create defer list pointer.
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deferType := llvm.PointerType(b.getLLVMRuntimeType("_defer"), 0)
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b.deferPtr = b.CreateAlloca(deferType, "deferPtr")
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b.CreateStore(llvm.ConstPointerNull(deferType), b.deferPtr)
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}
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// isInLoop checks if there is a path from a basic block to itself.
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func isInLoop(start *ssa.BasicBlock) bool {
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// Use a breadth-first search to scan backwards through the block graph.
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queue := []*ssa.BasicBlock{start}
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checked := map[*ssa.BasicBlock]struct{}{}
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for len(queue) > 0 {
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// pop a block off of the queue
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block := queue[len(queue)-1]
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queue = queue[:len(queue)-1]
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// Search through predecessors.
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// Searching backwards means that this is pretty fast when the block is close to the start of the function.
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// Defers are often placed near the start of the function.
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for _, pred := range block.Preds {
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if pred == start {
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// cycle found
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return true
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}
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if _, ok := checked[pred]; ok {
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// block already checked
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continue
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}
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// add to queue and checked map
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queue = append(queue, pred)
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checked[pred] = struct{}{}
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}
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}
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return false
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}
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// createDefer emits a single defer instruction, to be run when this function
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// returns.
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func (b *builder) createDefer(instr *ssa.Defer) {
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// The pointer to the previous defer struct, which we will replace to
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// make a linked list.
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next := b.CreateLoad(b.deferPtr, "defer.next")
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var values []llvm.Value
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valueTypes := []llvm.Type{b.uintptrType, next.Type()}
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if instr.Call.IsInvoke() {
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// Method call on an interface.
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// Get callback type number.
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methodName := instr.Call.Method.FullName()
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if _, ok := b.deferInvokeFuncs[methodName]; !ok {
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b.deferInvokeFuncs[methodName] = len(b.allDeferFuncs)
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b.allDeferFuncs = append(b.allDeferFuncs, &instr.Call)
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}
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callback := llvm.ConstInt(b.uintptrType, uint64(b.deferInvokeFuncs[methodName]), false)
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// Collect all values to be put in the struct (starting with
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// runtime._defer fields, followed by the call parameters).
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itf := b.getValue(instr.Call.Value) // interface
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typecode := b.CreateExtractValue(itf, 0, "invoke.func.typecode")
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receiverValue := b.CreateExtractValue(itf, 1, "invoke.func.receiver")
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values = []llvm.Value{callback, next, typecode, receiverValue}
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valueTypes = append(valueTypes, b.uintptrType, b.i8ptrType)
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for _, arg := range instr.Call.Args {
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val := b.getValue(arg)
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values = append(values, val)
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valueTypes = append(valueTypes, val.Type())
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}
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} else if callee, ok := instr.Call.Value.(*ssa.Function); ok {
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// Regular function call.
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if _, ok := b.deferFuncs[callee]; !ok {
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b.deferFuncs[callee] = len(b.allDeferFuncs)
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b.allDeferFuncs = append(b.allDeferFuncs, callee)
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}
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callback := llvm.ConstInt(b.uintptrType, uint64(b.deferFuncs[callee]), false)
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// Collect all values to be put in the struct (starting with
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// runtime._defer fields).
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values = []llvm.Value{callback, next}
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for _, param := range instr.Call.Args {
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llvmParam := b.getValue(param)
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values = append(values, llvmParam)
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valueTypes = append(valueTypes, llvmParam.Type())
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}
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} else if makeClosure, ok := instr.Call.Value.(*ssa.MakeClosure); ok {
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// Immediately applied function literal with free variables.
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// Extract the context from the closure. We won't need the function
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// pointer.
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// TODO: ignore this closure entirely and put pointers to the free
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// variables directly in the defer struct, avoiding a memory allocation.
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closure := b.getValue(instr.Call.Value)
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context := b.CreateExtractValue(closure, 0, "")
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// Get the callback number.
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fn := makeClosure.Fn.(*ssa.Function)
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if _, ok := b.deferClosureFuncs[fn]; !ok {
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b.deferClosureFuncs[fn] = len(b.allDeferFuncs)
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b.allDeferFuncs = append(b.allDeferFuncs, makeClosure)
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}
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callback := llvm.ConstInt(b.uintptrType, uint64(b.deferClosureFuncs[fn]), false)
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// Collect all values to be put in the struct (starting with
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// runtime._defer fields, followed by all parameters including the
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// context pointer).
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values = []llvm.Value{callback, next}
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for _, param := range instr.Call.Args {
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llvmParam := b.getValue(param)
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values = append(values, llvmParam)
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valueTypes = append(valueTypes, llvmParam.Type())
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}
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values = append(values, context)
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valueTypes = append(valueTypes, context.Type())
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} else if builtin, ok := instr.Call.Value.(*ssa.Builtin); ok {
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var argTypes []types.Type
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var argValues []llvm.Value
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for _, arg := range instr.Call.Args {
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argTypes = append(argTypes, arg.Type())
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argValues = append(argValues, b.getValue(arg))
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}
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if _, ok := b.deferBuiltinFuncs[instr.Call.Value]; !ok {
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b.deferBuiltinFuncs[instr.Call.Value] = deferBuiltin{
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callName: builtin.Name(),
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pos: builtin.Pos(),
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argTypes: argTypes,
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callback: len(b.allDeferFuncs),
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}
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b.allDeferFuncs = append(b.allDeferFuncs, instr.Call.Value)
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}
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callback := llvm.ConstInt(b.uintptrType, uint64(b.deferBuiltinFuncs[instr.Call.Value].callback), false)
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// Collect all values to be put in the struct (starting with
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// runtime._defer fields).
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values = []llvm.Value{callback, next}
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for _, param := range argValues {
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values = append(values, param)
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valueTypes = append(valueTypes, param.Type())
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}
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} else {
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funcValue := b.getValue(instr.Call.Value)
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if _, ok := b.deferExprFuncs[instr.Call.Value]; !ok {
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b.deferExprFuncs[instr.Call.Value] = len(b.allDeferFuncs)
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b.allDeferFuncs = append(b.allDeferFuncs, &instr.Call)
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}
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callback := llvm.ConstInt(b.uintptrType, uint64(b.deferExprFuncs[instr.Call.Value]), false)
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// Collect all values to be put in the struct (starting with
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// runtime._defer fields, followed by all parameters including the
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// context pointer).
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values = []llvm.Value{callback, next, funcValue}
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valueTypes = append(valueTypes, funcValue.Type())
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for _, param := range instr.Call.Args {
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llvmParam := b.getValue(param)
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values = append(values, llvmParam)
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valueTypes = append(valueTypes, llvmParam.Type())
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}
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}
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// Make a struct out of the collected values to put in the defer frame.
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deferFrameType := b.ctx.StructType(valueTypes, false)
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deferFrame := llvm.ConstNull(deferFrameType)
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for i, value := range values {
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deferFrame = b.CreateInsertValue(deferFrame, value, i, "")
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}
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// Put this struct in an allocation.
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var alloca llvm.Value
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if !isInLoop(instr.Block()) {
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// This can safely use a stack allocation.
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alloca = llvmutil.CreateEntryBlockAlloca(b.Builder, deferFrameType, "defer.alloca")
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} else {
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// This may be hit a variable number of times, so use a heap allocation.
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size := b.targetData.TypeAllocSize(deferFrameType)
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sizeValue := llvm.ConstInt(b.uintptrType, size, false)
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allocCall := b.createRuntimeCall("alloc", []llvm.Value{sizeValue}, "defer.alloc.call")
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alloca = b.CreateBitCast(allocCall, llvm.PointerType(deferFrameType, 0), "defer.alloc")
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}
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if b.NeedsStackObjects() {
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b.trackPointer(alloca)
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}
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b.CreateStore(deferFrame, alloca)
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// Push it on top of the linked list by replacing deferPtr.
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allocaCast := b.CreateBitCast(alloca, next.Type(), "defer.alloca.cast")
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b.CreateStore(allocaCast, b.deferPtr)
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}
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// createRunDefers emits code to run all deferred functions.
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func (b *builder) createRunDefers() {
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// Add a loop like the following:
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// for stack != nil {
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// _stack := stack
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// stack = stack.next
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// switch _stack.callback {
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// case 0:
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// // run first deferred call
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// case 1:
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// // run second deferred call
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// // etc.
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// default:
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// unreachable
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// }
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// }
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// Create loop.
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loophead := b.ctx.AddBasicBlock(b.llvmFn, "rundefers.loophead")
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loop := b.ctx.AddBasicBlock(b.llvmFn, "rundefers.loop")
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unreachable := b.ctx.AddBasicBlock(b.llvmFn, "rundefers.default")
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end := b.ctx.AddBasicBlock(b.llvmFn, "rundefers.end")
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b.CreateBr(loophead)
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// Create loop head:
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// for stack != nil {
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b.SetInsertPointAtEnd(loophead)
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deferData := b.CreateLoad(b.deferPtr, "")
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stackIsNil := b.CreateICmp(llvm.IntEQ, deferData, llvm.ConstPointerNull(deferData.Type()), "stackIsNil")
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b.CreateCondBr(stackIsNil, end, loop)
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// Create loop body:
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// _stack := stack
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// stack = stack.next
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// switch stack.callback {
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b.SetInsertPointAtEnd(loop)
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nextStackGEP := b.CreateInBoundsGEP(deferData, []llvm.Value{
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llvm.ConstInt(b.ctx.Int32Type(), 0, false),
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llvm.ConstInt(b.ctx.Int32Type(), 1, false), // .next field
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}, "stack.next.gep")
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nextStack := b.CreateLoad(nextStackGEP, "stack.next")
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b.CreateStore(nextStack, b.deferPtr)
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gep := b.CreateInBoundsGEP(deferData, []llvm.Value{
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llvm.ConstInt(b.ctx.Int32Type(), 0, false),
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llvm.ConstInt(b.ctx.Int32Type(), 0, false), // .callback field
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}, "callback.gep")
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callback := b.CreateLoad(gep, "callback")
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sw := b.CreateSwitch(callback, unreachable, len(b.allDeferFuncs))
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for i, callback := range b.allDeferFuncs {
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// Create switch case, for example:
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// case 0:
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// // run first deferred call
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block := b.ctx.AddBasicBlock(b.llvmFn, "rundefers.callback")
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sw.AddCase(llvm.ConstInt(b.uintptrType, uint64(i), false), block)
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b.SetInsertPointAtEnd(block)
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switch callback := callback.(type) {
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case *ssa.CallCommon:
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// Call on an value or interface value.
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// Get the real defer struct type and cast to it.
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valueTypes := []llvm.Type{b.uintptrType, llvm.PointerType(b.getLLVMRuntimeType("_defer"), 0)}
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if !callback.IsInvoke() {
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//Expect funcValue to be passed through the defer frame.
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valueTypes = append(valueTypes, b.getFuncType(callback.Signature()))
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} else {
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//Expect typecode
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valueTypes = append(valueTypes, b.uintptrType, b.i8ptrType)
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}
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for _, arg := range callback.Args {
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valueTypes = append(valueTypes, b.getLLVMType(arg.Type()))
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}
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deferFrameType := b.ctx.StructType(valueTypes, false)
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deferFramePtr := b.CreateBitCast(deferData, llvm.PointerType(deferFrameType, 0), "deferFrame")
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// Extract the params from the struct (including receiver).
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forwardParams := []llvm.Value{}
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zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
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for i := 2; i < len(valueTypes); i++ {
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gep := b.CreateInBoundsGEP(deferFramePtr, []llvm.Value{zero, llvm.ConstInt(b.ctx.Int32Type(), uint64(i), false)}, "gep")
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forwardParam := b.CreateLoad(gep, "param")
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forwardParams = append(forwardParams, forwardParam)
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}
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var fnPtr llvm.Value
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if !callback.IsInvoke() {
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// Isolate the func value.
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funcValue := forwardParams[0]
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forwardParams = forwardParams[1:]
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//Get function pointer and context
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fp, context := b.decodeFuncValue(funcValue, callback.Signature())
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fnPtr = fp
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//Pass context
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forwardParams = append(forwardParams, context)
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} else {
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// Isolate the typecode.
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typecode := forwardParams[0]
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forwardParams = forwardParams[1:]
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fnPtr = b.getInvokePtr(callback, typecode)
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// Add the context parameter. An interface call cannot also be a
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// closure but we have to supply the parameter anyway for platforms
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// with a strict calling convention.
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forwardParams = append(forwardParams, llvm.Undef(b.i8ptrType))
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}
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// Parent coroutine handle.
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forwardParams = append(forwardParams, llvm.Undef(b.i8ptrType))
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b.createCall(fnPtr, forwardParams, "")
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case *ssa.Function:
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// Direct call.
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// Get the real defer struct type and cast to it.
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valueTypes := []llvm.Type{b.uintptrType, llvm.PointerType(b.getLLVMRuntimeType("_defer"), 0)}
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for _, param := range callback.Params {
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valueTypes = append(valueTypes, b.getLLVMType(param.Type()))
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}
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deferFrameType := b.ctx.StructType(valueTypes, false)
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deferFramePtr := b.CreateBitCast(deferData, llvm.PointerType(deferFrameType, 0), "deferFrame")
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// Extract the params from the struct.
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forwardParams := []llvm.Value{}
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zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
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for i := range callback.Params {
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gep := b.CreateInBoundsGEP(deferFramePtr, []llvm.Value{zero, llvm.ConstInt(b.ctx.Int32Type(), uint64(i+2), false)}, "gep")
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forwardParam := b.CreateLoad(gep, "param")
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forwardParams = append(forwardParams, forwardParam)
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}
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// Plain TinyGo functions add some extra parameters to implement async functionality and function recievers.
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// These parameters should not be supplied when calling into an external C/ASM function.
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if !b.getFunctionInfo(callback).exported {
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// Add the context parameter. We know it is ignored by the receiving
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// function, but we have to pass one anyway.
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forwardParams = append(forwardParams, llvm.Undef(b.i8ptrType))
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// Parent coroutine handle.
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forwardParams = append(forwardParams, llvm.Undef(b.i8ptrType))
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}
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// Call real function.
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b.createCall(b.getFunction(callback), forwardParams, "")
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case *ssa.MakeClosure:
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// Get the real defer struct type and cast to it.
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fn := callback.Fn.(*ssa.Function)
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valueTypes := []llvm.Type{b.uintptrType, llvm.PointerType(b.getLLVMRuntimeType("_defer"), 0)}
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params := fn.Signature.Params()
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for i := 0; i < params.Len(); i++ {
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valueTypes = append(valueTypes, b.getLLVMType(params.At(i).Type()))
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}
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valueTypes = append(valueTypes, b.i8ptrType) // closure
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deferFrameType := b.ctx.StructType(valueTypes, false)
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deferFramePtr := b.CreateBitCast(deferData, llvm.PointerType(deferFrameType, 0), "deferFrame")
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// Extract the params from the struct.
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forwardParams := []llvm.Value{}
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zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
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for i := 2; i < len(valueTypes); i++ {
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gep := b.CreateInBoundsGEP(deferFramePtr, []llvm.Value{zero, llvm.ConstInt(b.ctx.Int32Type(), uint64(i), false)}, "")
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forwardParam := b.CreateLoad(gep, "param")
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forwardParams = append(forwardParams, forwardParam)
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}
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// Parent coroutine handle.
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forwardParams = append(forwardParams, llvm.Undef(b.i8ptrType))
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// Call deferred function.
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b.createCall(b.getFunction(fn), forwardParams, "")
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case *ssa.Builtin:
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db := b.deferBuiltinFuncs[callback]
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//Get parameter types
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valueTypes := []llvm.Type{b.uintptrType, llvm.PointerType(b.getLLVMRuntimeType("_defer"), 0)}
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//Get signature from call results
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params := callback.Type().Underlying().(*types.Signature).Params()
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for i := 0; i < params.Len(); i++ {
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valueTypes = append(valueTypes, b.getLLVMType(params.At(i).Type()))
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}
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deferFrameType := b.ctx.StructType(valueTypes, false)
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deferFramePtr := b.CreateBitCast(deferData, llvm.PointerType(deferFrameType, 0), "deferFrame")
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// Extract the params from the struct.
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var argValues []llvm.Value
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zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
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for i := 0; i < params.Len(); i++ {
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gep := b.CreateInBoundsGEP(deferFramePtr, []llvm.Value{zero, llvm.ConstInt(b.ctx.Int32Type(), uint64(i+2), false)}, "gep")
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forwardParam := b.CreateLoad(gep, "param")
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argValues = append(argValues, forwardParam)
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}
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_, err := b.createBuiltin(db.argTypes, argValues, db.callName, db.pos)
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if err != nil {
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b.diagnostics = append(b.diagnostics, err)
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}
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default:
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panic("unknown deferred function type")
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}
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// Branch back to the start of the loop.
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b.CreateBr(loophead)
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}
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// Create default unreachable block:
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// default:
|
|
// unreachable
|
|
// }
|
|
b.SetInsertPointAtEnd(unreachable)
|
|
b.CreateUnreachable()
|
|
|
|
// End of loop.
|
|
b.SetInsertPointAtEnd(end)
|
|
}
|