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compiler: refactor alloca/lifetime/wordpack code into separate package
This code is required by transformation passes which are being moved into a separate package, but is too complicated to simply copy. Therefore, I decided to move them into a new package.
This commit is contained in:
Ayke van Laethem
@@ -0,0 +1,96 @@
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// Package llvmutil contains utility functions used across multiple compiler
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// packages. For example, they may be used by both the compiler pacakge and
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// transformation packages.
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//
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// Normally, utility packages are avoided. However, in this case, the utility
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// functions are non-trivial and hard to get right. Copying them to multiple
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// places would be a big risk if only one of them is updated.
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package llvmutil
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import "tinygo.org/x/go-llvm"
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// CreateEntryBlockAlloca creates a new alloca in the entry block, even though
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// the IR builder is located elsewhere. It assumes that the insert point is
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// at the end of the current block.
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func CreateEntryBlockAlloca(builder llvm.Builder, t llvm.Type, name string) llvm.Value {
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currentBlock := builder.GetInsertBlock()
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entryBlock := currentBlock.Parent().EntryBasicBlock()
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if entryBlock.FirstInstruction().IsNil() {
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builder.SetInsertPointAtEnd(entryBlock)
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} else {
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builder.SetInsertPointBefore(entryBlock.FirstInstruction())
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}
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alloca := builder.CreateAlloca(t, name)
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builder.SetInsertPointAtEnd(currentBlock)
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return alloca
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}
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// CreateTemporaryAlloca creates a new alloca in the entry block and adds
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// lifetime start infromation in the IR signalling that the alloca won't be used
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// before this point.
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//
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// This is useful for creating temporary allocas for intrinsics. Don't forget to
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// end the lifetime using emitLifetimeEnd after you're done with it.
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func CreateTemporaryAlloca(builder llvm.Builder, mod llvm.Module, t llvm.Type, name string) (alloca, bitcast, size llvm.Value) {
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ctx := t.Context()
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targetData := llvm.NewTargetData(mod.DataLayout())
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i8ptrType := llvm.PointerType(ctx.Int8Type(), 0)
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alloca = CreateEntryBlockAlloca(builder, t, name)
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bitcast = builder.CreateBitCast(alloca, i8ptrType, name+".bitcast")
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size = llvm.ConstInt(ctx.Int64Type(), targetData.TypeAllocSize(t), false)
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builder.CreateCall(getLifetimeStartFunc(mod), []llvm.Value{size, bitcast}, "")
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return
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}
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// CreateInstructionAlloca creates an alloca in the entry block, and places lifetime control intrinsics around the instruction
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func CreateInstructionAlloca(builder llvm.Builder, mod llvm.Module, t llvm.Type, inst llvm.Value, name string) llvm.Value {
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ctx := mod.Context()
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targetData := llvm.NewTargetData(mod.DataLayout())
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i8ptrType := llvm.PointerType(ctx.Int8Type(), 0)
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alloca := CreateEntryBlockAlloca(builder, t, name)
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builder.SetInsertPointBefore(inst)
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bitcast := builder.CreateBitCast(alloca, i8ptrType, name+".bitcast")
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size := llvm.ConstInt(ctx.Int64Type(), targetData.TypeAllocSize(t), false)
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builder.CreateCall(getLifetimeStartFunc(mod), []llvm.Value{size, bitcast}, "")
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if next := llvm.NextInstruction(inst); !next.IsNil() {
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builder.SetInsertPointBefore(next)
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} else {
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builder.SetInsertPointAtEnd(inst.InstructionParent())
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}
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builder.CreateCall(getLifetimeEndFunc(mod), []llvm.Value{size, bitcast}, "")
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return alloca
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}
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// EmitLifetimeEnd signals the end of an (alloca) lifetime by calling the
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// llvm.lifetime.end intrinsic. It is commonly used together with
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// createTemporaryAlloca.
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func EmitLifetimeEnd(builder llvm.Builder, mod llvm.Module, ptr, size llvm.Value) {
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builder.CreateCall(getLifetimeEndFunc(mod), []llvm.Value{size, ptr}, "")
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}
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// getLifetimeStartFunc returns the llvm.lifetime.start intrinsic and creates it
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// first if it doesn't exist yet.
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func getLifetimeStartFunc(mod llvm.Module) llvm.Value {
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fn := mod.NamedFunction("llvm.lifetime.start.p0i8")
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ctx := mod.Context()
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i8ptrType := llvm.PointerType(ctx.Int8Type(), 0)
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if fn.IsNil() {
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fnType := llvm.FunctionType(ctx.VoidType(), []llvm.Type{ctx.Int64Type(), i8ptrType}, false)
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fn = llvm.AddFunction(mod, "llvm.lifetime.start.p0i8", fnType)
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}
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return fn
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}
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// getLifetimeEndFunc returns the llvm.lifetime.end intrinsic and creates it
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// first if it doesn't exist yet.
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func getLifetimeEndFunc(mod llvm.Module) llvm.Value {
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fn := mod.NamedFunction("llvm.lifetime.end.p0i8")
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ctx := mod.Context()
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i8ptrType := llvm.PointerType(ctx.Int8Type(), 0)
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if fn.IsNil() {
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fnType := llvm.FunctionType(ctx.VoidType(), []llvm.Type{ctx.Int64Type(), i8ptrType}, false)
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fn = llvm.AddFunction(mod, "llvm.lifetime.end.p0i8", fnType)
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}
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return fn
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}
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@@ -0,0 +1,133 @@
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package llvmutil
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// This file contains utility functions to pack and unpack sets of values. It
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// can take in a list of values and tries to store it efficiently in the pointer
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// itself if possible and legal.
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import (
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"github.com/tinygo-org/tinygo/compileopts"
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"tinygo.org/x/go-llvm"
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)
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// EmitPointerPack packs the list of values into a single pointer value using
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// bitcasts, or else allocates a value on the heap if it cannot be packed in the
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// pointer value directly. It returns the pointer with the packed data.
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func EmitPointerPack(builder llvm.Builder, mod llvm.Module, config *compileopts.Config, values []llvm.Value) llvm.Value {
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ctx := mod.Context()
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targetData := llvm.NewTargetData(mod.DataLayout())
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i8ptrType := llvm.PointerType(mod.Context().Int8Type(), 0)
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uintptrType := ctx.IntType(llvm.NewTargetData(mod.DataLayout()).PointerSize() * 8)
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valueTypes := make([]llvm.Type, len(values))
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for i, value := range values {
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valueTypes[i] = value.Type()
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}
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packedType := ctx.StructType(valueTypes, false)
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// Allocate memory for the packed data.
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var packedAlloc, packedHeapAlloc llvm.Value
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size := targetData.TypeAllocSize(packedType)
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if size == 0 {
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return llvm.ConstPointerNull(i8ptrType)
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} else if len(values) == 1 && values[0].Type().TypeKind() == llvm.PointerTypeKind {
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return builder.CreateBitCast(values[0], i8ptrType, "pack.ptr")
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} else if size <= targetData.TypeAllocSize(i8ptrType) {
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// Packed data fits in a pointer, so store it directly inside the
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// pointer.
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if len(values) == 1 && values[0].Type().TypeKind() == llvm.IntegerTypeKind {
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// Try to keep this cast in SSA form.
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return builder.CreateIntToPtr(values[0], i8ptrType, "pack.int")
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}
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// Because packedType is a struct and we have to cast it to a *i8, store
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// it in an alloca first for bitcasting (store+bitcast+load).
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packedAlloc, _, _ = CreateTemporaryAlloca(builder, mod, packedType, "")
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} else {
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// Packed data is bigger than a pointer, so allocate it on the heap.
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sizeValue := llvm.ConstInt(uintptrType, size, false)
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alloc := mod.NamedFunction("runtime.alloc")
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packedHeapAlloc = builder.CreateCall(alloc, []llvm.Value{sizeValue}, "")
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if config.NeedsStackObjects() {
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trackPointer := mod.NamedFunction("runtime.trackPointer")
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builder.CreateCall(trackPointer, []llvm.Value{packedHeapAlloc}, "")
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}
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packedAlloc = builder.CreateBitCast(packedHeapAlloc, llvm.PointerType(packedType, 0), "")
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}
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// Store all values in the alloca or heap pointer.
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for i, value := range values {
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indices := []llvm.Value{
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llvm.ConstInt(ctx.Int32Type(), 0, false),
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llvm.ConstInt(ctx.Int32Type(), uint64(i), false),
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}
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gep := builder.CreateInBoundsGEP(packedAlloc, indices, "")
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builder.CreateStore(value, gep)
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}
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if packedHeapAlloc.IsNil() {
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// Load value (as *i8) from the alloca.
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packedAlloc = builder.CreateBitCast(packedAlloc, llvm.PointerType(i8ptrType, 0), "")
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result := builder.CreateLoad(packedAlloc, "")
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packedPtr := builder.CreateBitCast(packedAlloc, i8ptrType, "")
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packedSize := llvm.ConstInt(ctx.Int64Type(), targetData.TypeAllocSize(packedAlloc.Type()), false)
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EmitLifetimeEnd(builder, mod, packedPtr, packedSize)
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return result
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} else {
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// Get the original heap allocation pointer, which already is an *i8.
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return packedHeapAlloc
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}
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}
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// EmitPointerUnpack extracts a list of values packed using EmitPointerPack.
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func EmitPointerUnpack(builder llvm.Builder, mod llvm.Module, ptr llvm.Value, valueTypes []llvm.Type) []llvm.Value {
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ctx := mod.Context()
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targetData := llvm.NewTargetData(mod.DataLayout())
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i8ptrType := llvm.PointerType(mod.Context().Int8Type(), 0)
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uintptrType := ctx.IntType(llvm.NewTargetData(mod.DataLayout()).PointerSize() * 8)
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packedType := ctx.StructType(valueTypes, false)
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// Get a correctly-typed pointer to the packed data.
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var packedAlloc, packedRawAlloc llvm.Value
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size := targetData.TypeAllocSize(packedType)
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if size == 0 {
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// No data to unpack.
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} else if len(valueTypes) == 1 && valueTypes[0].TypeKind() == llvm.PointerTypeKind {
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// A single pointer is always stored directly.
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return []llvm.Value{builder.CreateBitCast(ptr, valueTypes[0], "unpack.ptr")}
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} else if size <= targetData.TypeAllocSize(i8ptrType) {
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// Packed data stored directly in pointer.
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if len(valueTypes) == 1 && valueTypes[0].TypeKind() == llvm.IntegerTypeKind {
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// Keep this cast in SSA form.
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return []llvm.Value{builder.CreatePtrToInt(ptr, valueTypes[0], "unpack.int")}
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}
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// Fallback: load it using an alloca.
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packedRawAlloc, _, _ = CreateTemporaryAlloca(builder, mod, llvm.PointerType(i8ptrType, 0), "unpack.raw.alloc")
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packedRawValue := builder.CreateBitCast(ptr, llvm.PointerType(i8ptrType, 0), "unpack.raw.value")
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builder.CreateStore(packedRawValue, packedRawAlloc)
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packedAlloc = builder.CreateBitCast(packedRawAlloc, llvm.PointerType(packedType, 0), "unpack.alloc")
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} else {
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// Packed data stored on the heap. Bitcast the passed-in pointer to the
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// correct pointer type.
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packedAlloc = builder.CreateBitCast(ptr, llvm.PointerType(packedType, 0), "unpack.raw.ptr")
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}
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// Load each value from the packed data.
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values := make([]llvm.Value, len(valueTypes))
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for i, valueType := range valueTypes {
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if targetData.TypeAllocSize(valueType) == 0 {
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// This value has length zero, so there's nothing to load.
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values[i] = llvm.ConstNull(valueType)
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continue
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}
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indices := []llvm.Value{
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llvm.ConstInt(ctx.Int32Type(), 0, false),
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llvm.ConstInt(ctx.Int32Type(), uint64(i), false),
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}
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gep := builder.CreateInBoundsGEP(packedAlloc, indices, "")
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values[i] = builder.CreateLoad(gep, "")
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}
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if !packedRawAlloc.IsNil() {
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allocPtr := builder.CreateBitCast(packedRawAlloc, i8ptrType, "")
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allocSize := llvm.ConstInt(ctx.Int64Type(), targetData.TypeAllocSize(uintptrType), false)
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EmitLifetimeEnd(builder, mod, allocPtr, allocSize)
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}
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return values
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}
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