compiler: remove ir package

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.
This commit is contained in:
Ayke van Laethem
2021-01-18 18:53:07 +01:00
committed by Ayke
parent 9bd36597d6
commit d8cc48b09b
14 changed files with 567 additions and 655 deletions
+212 -1
View File
@@ -15,6 +15,197 @@ import (
"tinygo.org/x/go-llvm"
)
// functionInfo contains some information about a function or method. In
// particular, it contains information obtained from pragmas.
//
// The linkName value contains a valid link name, even if //go:linkname is not
// present.
type functionInfo struct {
module string // go:wasm-module
linkName string // go:linkname, go:export
exported bool // go:export, CGo
nobounds bool // go:nobounds
inline inlineType // go:inline
}
type inlineType int
// How much to inline.
const (
// Default behavior. The compiler decides for itself whether any given
// function will be inlined. Whether any function is inlined depends on the
// optimization level.
inlineDefault inlineType = iota
// Inline hint, just like the C inline keyword (signalled using
// //go:inline). The compiler will be more likely to inline this function,
// but it is not a guarantee.
inlineHint
// Don't inline, just like the GCC noinline attribute. Signalled using
// //go:noinline.
inlineNone
)
// getFunction returns the LLVM function for the given *ssa.Function, creating
// it if needed. It can later be filled with compilerContext.createFunction().
func (c *compilerContext) getFunction(fn *ssa.Function) llvm.Value {
info := c.getFunctionInfo(fn)
llvmFn := c.mod.NamedFunction(info.linkName)
if !llvmFn.IsNil() {
return llvmFn
}
var retType llvm.Type
if fn.Signature.Results() == nil {
retType = c.ctx.VoidType()
} else if fn.Signature.Results().Len() == 1 {
retType = c.getLLVMType(fn.Signature.Results().At(0).Type())
} else {
results := make([]llvm.Type, 0, fn.Signature.Results().Len())
for i := 0; i < fn.Signature.Results().Len(); i++ {
results = append(results, c.getLLVMType(fn.Signature.Results().At(i).Type()))
}
retType = c.ctx.StructType(results, false)
}
var paramInfos []paramInfo
for _, param := range fn.Params {
paramType := c.getLLVMType(param.Type())
paramFragmentInfos := expandFormalParamType(paramType, param.Name(), param.Type())
paramInfos = append(paramInfos, paramFragmentInfos...)
}
// Add an extra parameter as the function context. This context is used in
// closures and bound methods, but should be optimized away when not used.
if !info.exported {
paramInfos = append(paramInfos, paramInfo{llvmType: c.i8ptrType, name: "context", flags: 0})
paramInfos = append(paramInfos, paramInfo{llvmType: c.i8ptrType, name: "parentHandle", flags: 0})
}
var paramTypes []llvm.Type
for _, info := range paramInfos {
paramTypes = append(paramTypes, info.llvmType)
}
fnType := llvm.FunctionType(retType, paramTypes, false)
llvmFn = llvm.AddFunction(c.mod, info.linkName, fnType)
dereferenceableOrNullKind := llvm.AttributeKindID("dereferenceable_or_null")
for i, info := range paramInfos {
if info.flags&paramIsDeferenceableOrNull == 0 {
continue
}
if info.llvmType.TypeKind() == llvm.PointerTypeKind {
el := info.llvmType.ElementType()
size := c.targetData.TypeAllocSize(el)
if size == 0 {
// dereferenceable_or_null(0) appears to be illegal in LLVM.
continue
}
dereferenceableOrNull := c.ctx.CreateEnumAttribute(dereferenceableOrNullKind, size)
llvmFn.AddAttributeAtIndex(i+1, dereferenceableOrNull)
}
}
// External/exported functions may not retain pointer values.
// https://golang.org/cmd/cgo/#hdr-Passing_pointers
if info.exported {
// Set the wasm-import-module attribute if the function's module is set.
if info.module != "" {
wasmImportModuleAttr := c.ctx.CreateStringAttribute("wasm-import-module", info.module)
llvmFn.AddFunctionAttr(wasmImportModuleAttr)
}
nocaptureKind := llvm.AttributeKindID("nocapture")
nocapture := c.ctx.CreateEnumAttribute(nocaptureKind, 0)
for i, typ := range paramTypes {
if typ.TypeKind() == llvm.PointerTypeKind {
llvmFn.AddAttributeAtIndex(i+1, nocapture)
}
}
}
return llvmFn
}
// getFunctionInfo returns information about a function that is not directly
// present in *ssa.Function, such as the link name and whether it should be
// exported.
func (c *compilerContext) getFunctionInfo(f *ssa.Function) functionInfo {
info := functionInfo{}
if strings.HasPrefix(f.Name(), "C.") {
// Created by CGo: such a name cannot be created by regular C code.
info.linkName = f.Name()[2:]
info.exported = true
} else {
// Pick the default linkName.
info.linkName = f.RelString(nil)
// Check for //go: pragmas, which may change the link name (among
// others).
info.parsePragmas(f)
}
return info
}
// parsePragmas is used by getFunctionInfo to parse function pragmas such as
// //export or //go:noinline.
func (info *functionInfo) parsePragmas(f *ssa.Function) {
if f.Syntax() == nil {
return
}
if decl, ok := f.Syntax().(*ast.FuncDecl); ok && decl.Doc != nil {
for _, comment := range decl.Doc.List {
text := comment.Text
if strings.HasPrefix(text, "//export ") {
// Rewrite '//export' to '//go:export' for compatibility with
// gc.
text = "//go:" + text[2:]
}
if !strings.HasPrefix(text, "//go:") {
continue
}
parts := strings.Fields(text)
switch parts[0] {
case "//go:export":
if len(parts) != 2 {
continue
}
info.linkName = parts[1]
info.exported = true
case "//go:wasm-module":
// Alternative comment for setting the import module.
if len(parts) != 2 {
continue
}
info.module = parts[1]
case "//go:inline":
info.inline = inlineHint
case "//go:noinline":
info.inline = inlineNone
case "//go:linkname":
if len(parts) != 3 || parts[1] != f.Name() {
continue
}
// Only enable go:linkname when the package imports "unsafe".
// This is a slightly looser requirement than what gc uses: gc
// requires the file to import "unsafe", not the package as a
// whole.
if hasUnsafeImport(f.Pkg.Pkg) {
info.linkName = parts[2]
}
case "//go:nobounds":
// Skip bounds checking in this function. Useful for some
// runtime functions.
// This is somewhat dangerous and thus only imported in packages
// that import unsafe.
if hasUnsafeImport(f.Pkg.Pkg) {
info.nobounds = true
}
}
}
}
}
// globalInfo contains some information about a specific global. By default,
// linkName is equal to .RelString(nil) on a global and extern is false, but for
// some symbols this is different (due to //go:extern for example).
@@ -86,7 +277,7 @@ func (c *compilerContext) getGlobal(g *ssa.Global) llvm.Value {
// Add debug info.
// TODO: this should be done for every global in the program, not just
// the ones that are referenced from some code.
pos := c.ir.Program.Fset.Position(g.Pos())
pos := c.program.Fset.Position(g.Pos())
diglobal := c.dibuilder.CreateGlobalVariableExpression(c.difiles[pos.Filename], llvm.DIGlobalVariableExpression{
Name: g.RelString(nil),
LinkageName: info.linkName,
@@ -145,3 +336,23 @@ func (info *globalInfo) parsePragmas(doc *ast.CommentGroup) {
}
}
}
// Get all methods of a type.
func getAllMethods(prog *ssa.Program, typ types.Type) []*types.Selection {
ms := prog.MethodSets.MethodSet(typ)
methods := make([]*types.Selection, ms.Len())
for i := 0; i < ms.Len(); i++ {
methods[i] = ms.At(i)
}
return methods
}
// Return true if this package imports "unsafe", false otherwise.
func hasUnsafeImport(pkg *types.Package) bool {
for _, imp := range pkg.Imports() {
if imp == types.Unsafe {
return true
}
}
return false
}