1 files changed, 341 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssagen/abi.go b/src/cmd/compile/internal/ssagen/abi.go
new file mode 100644
index 0000000..84d5b59
--- /dev/null
+++ b/src/cmd/compile/internal/ssagen/abi.go
@@ -0,0 +1,341 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssagen
+
+import (
+	"fmt"
+	"internal/buildcfg"
+	"log"
+	"os"
+	"strings"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/obj"
+)
+
+// SymABIs records information provided by the assembler about symbol
+// definition ABIs and reference ABIs.
+type SymABIs struct {
+	defs map[string]obj.ABI
+	refs map[string]obj.ABISet
+}
+
+func NewSymABIs() *SymABIs {
+	return &SymABIs{
+		defs: make(map[string]obj.ABI),
+		refs: make(map[string]obj.ABISet),
+	}
+}
+
+// canonicalize returns the canonical name used for a linker symbol in
+// s's maps. Symbols in this package may be written either as "".X or
+// with the package's import path already in the symbol. This rewrites
+// both to use the full path, which matches compiler-generated linker
+// symbol names.
+func (s *SymABIs) canonicalize(linksym string) string {
+	// If the symbol is already prefixed with "", rewrite it to start
+	// with LocalPkg.Prefix.
+	//
+	// TODO(mdempsky): Have cmd/asm stop writing out symbols like this.
+	if strings.HasPrefix(linksym, `"".`) {
+		return types.LocalPkg.Prefix + linksym[2:]
+	}
+	return linksym
+}
+
+// ReadSymABIs reads a symabis file that specifies definitions and
+// references of text symbols by ABI.
+//
+// The symabis format is a set of lines, where each line is a sequence
+// of whitespace-separated fields. The first field is a verb and is
+// either "def" for defining a symbol ABI or "ref" for referencing a
+// symbol using an ABI. For both "def" and "ref", the second field is
+// the symbol name and the third field is the ABI name, as one of the
+// named cmd/internal/obj.ABI constants.
+func (s *SymABIs) ReadSymABIs(file string) {
+	data, err := os.ReadFile(file)
+	if err != nil {
+		log.Fatalf("-symabis: %v", err)
+	}
+
+	for lineNum, line := range strings.Split(string(data), "\n") {
+		lineNum++ // 1-based
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		parts := strings.Fields(line)
+		switch parts[0] {
+		case "def", "ref":
+			// Parse line.
+			if len(parts) != 3 {
+				log.Fatalf(`%s:%d: invalid symabi: syntax is "%s sym abi"`, file, lineNum, parts[0])
+			}
+			sym, abistr := parts[1], parts[2]
+			abi, valid := obj.ParseABI(abistr)
+			if !valid {
+				log.Fatalf(`%s:%d: invalid symabi: unknown abi "%s"`, file, lineNum, abistr)
+			}
+
+			sym = s.canonicalize(sym)
+
+			// Record for later.
+			if parts[0] == "def" {
+				s.defs[sym] = abi
+			} else {
+				s.refs[sym] |= obj.ABISetOf(abi)
+			}
+		default:
+			log.Fatalf(`%s:%d: invalid symabi type "%s"`, file, lineNum, parts[0])
+		}
+	}
+}
+
+// GenABIWrappers applies ABI information to Funcs and generates ABI
+// wrapper functions where necessary.
+func (s *SymABIs) GenABIWrappers() {
+	// For cgo exported symbols, we tell the linker to export the
+	// definition ABI to C. That also means that we don't want to
+	// create ABI wrappers even if there's a linkname.
+	//
+	// TODO(austin): Maybe we want to create the ABI wrappers, but
+	// ensure the linker exports the right ABI definition under
+	// the unmangled name?
+	cgoExports := make(map[string][]*[]string)
+	for i, prag := range typecheck.Target.CgoPragmas {
+		switch prag[0] {
+		case "cgo_export_static", "cgo_export_dynamic":
+			symName := s.canonicalize(prag[1])
+			pprag := &typecheck.Target.CgoPragmas[i]
+			cgoExports[symName] = append(cgoExports[symName], pprag)
+		}
+	}
+
+	// Apply ABI defs and refs to Funcs and generate wrappers.
+	//
+	// This may generate new decls for the wrappers, but we
+	// specifically *don't* want to visit those, lest we create
+	// wrappers for wrappers.
+	for _, fn := range typecheck.Target.Decls {
+		if fn.Op() != ir.ODCLFUNC {
+			continue
+		}
+		fn := fn.(*ir.Func)
+		nam := fn.Nname
+		if ir.IsBlank(nam) {
+			continue
+		}
+		sym := nam.Sym()
+
+		symName := sym.Linkname
+		if symName == "" {
+			symName = sym.Pkg.Prefix + "." + sym.Name
+		}
+		symName = s.canonicalize(symName)
+
+		// Apply definitions.
+		defABI, hasDefABI := s.defs[symName]
+		if hasDefABI {
+			if len(fn.Body) != 0 {
+				base.ErrorfAt(fn.Pos(), "%v defined in both Go and assembly", fn)
+			}
+			fn.ABI = defABI
+		}
+
+		if fn.Pragma&ir.CgoUnsafeArgs != 0 {
+			// CgoUnsafeArgs indicates the function (or its callee) uses
+			// offsets to dispatch arguments, which currently using ABI0
+			// frame layout. Pin it to ABI0.
+			fn.ABI = obj.ABI0
+		}
+
+		// If cgo-exported, add the definition ABI to the cgo
+		// pragmas.
+		cgoExport := cgoExports[symName]
+		for _, pprag := range cgoExport {
+			// The export pragmas have the form:
+			//
+			//   cgo_export_* <local> [<remote>]
+			//
+			// If <remote> is omitted, it's the same as
+			// <local>.
+			//
+			// Expand to
+			//
+			//   cgo_export_* <local> <remote> <ABI>
+			if len(*pprag) == 2 {
+				*pprag = append(*pprag, (*pprag)[1])
+			}
+			// Add the ABI argument.
+			*pprag = append(*pprag, fn.ABI.String())
+		}
+
+		// Apply references.
+		if abis, ok := s.refs[symName]; ok {
+			fn.ABIRefs |= abis
+		}
+		// Assume all functions are referenced at least as
+		// ABIInternal, since they may be referenced from
+		// other packages.
+		fn.ABIRefs.Set(obj.ABIInternal, true)
+
+		// If a symbol is defined in this package (either in
+		// Go or assembly) and given a linkname, it may be
+		// referenced from another package, so make it
+		// callable via any ABI. It's important that we know
+		// it's defined in this package since other packages
+		// may "pull" symbols using linkname and we don't want
+		// to create duplicate ABI wrappers.
+		//
+		// However, if it's given a linkname for exporting to
+		// C, then we don't make ABI wrappers because the cgo
+		// tool wants the original definition.
+		hasBody := len(fn.Body) != 0
+		if sym.Linkname != "" && (hasBody || hasDefABI) && len(cgoExport) == 0 {
+			fn.ABIRefs |= obj.ABISetCallable
+		}
+
+		// Double check that cgo-exported symbols don't get
+		// any wrappers.
+		if len(cgoExport) > 0 && fn.ABIRefs&^obj.ABISetOf(fn.ABI) != 0 {
+			base.Fatalf("cgo exported function %v cannot have ABI wrappers", fn)
+		}
+
+		if !buildcfg.Experiment.RegabiWrappers {
+			continue
+		}
+
+		forEachWrapperABI(fn, makeABIWrapper)
+	}
+}
+
+func forEachWrapperABI(fn *ir.Func, cb func(fn *ir.Func, wrapperABI obj.ABI)) {
+	need := fn.ABIRefs &^ obj.ABISetOf(fn.ABI)
+	if need == 0 {
+		return
+	}
+
+	for wrapperABI := obj.ABI(0); wrapperABI < obj.ABICount; wrapperABI++ {
+		if !need.Get(wrapperABI) {
+			continue
+		}
+		cb(fn, wrapperABI)
+	}
+}
+
+// makeABIWrapper creates a new function that will be called with
+// wrapperABI and calls "f" using f.ABI.
+func makeABIWrapper(f *ir.Func, wrapperABI obj.ABI) {
+	if base.Debug.ABIWrap != 0 {
+		fmt.Fprintf(os.Stderr, "=-= %v to %v wrapper for %v\n", wrapperABI, f.ABI, f)
+	}
+
+	// Q: is this needed?
+	savepos := base.Pos
+	savedclcontext := typecheck.DeclContext
+	savedcurfn := ir.CurFunc
+
+	base.Pos = base.AutogeneratedPos
+	typecheck.DeclContext = ir.PEXTERN
+
+	// At the moment we don't support wrapping a method, we'd need machinery
+	// below to handle the receiver. Panic if we see this scenario.
+	ft := f.Nname.Type()
+	if ft.NumRecvs() != 0 {
+		base.ErrorfAt(f.Pos(), "makeABIWrapper support for wrapping methods not implemented")
+		return
+	}
+
+	// Reuse f's types.Sym to create a new ODCLFUNC/function.
+	fn := typecheck.DeclFunc(f.Nname.Sym(), nil,
+		typecheck.NewFuncParams(ft.Params(), true),
+		typecheck.NewFuncParams(ft.Results(), false))
+	fn.ABI = wrapperABI
+
+	fn.SetABIWrapper(true)
+	fn.SetDupok(true)
+
+	// ABI0-to-ABIInternal wrappers will be mainly loading params from
+	// stack into registers (and/or storing stack locations back to
+	// registers after the wrapped call); in most cases they won't
+	// need to allocate stack space, so it should be OK to mark them
+	// as NOSPLIT in these cases. In addition, my assumption is that
+	// functions written in assembly are NOSPLIT in most (but not all)
+	// cases. In the case of an ABIInternal target that has too many
+	// parameters to fit into registers, the wrapper would need to
+	// allocate stack space, but this seems like an unlikely scenario.
+	// Hence: mark these wrappers NOSPLIT.
+	//
+	// ABIInternal-to-ABI0 wrappers on the other hand will be taking
+	// things in registers and pushing them onto the stack prior to
+	// the ABI0 call, meaning that they will always need to allocate
+	// stack space. If the compiler marks them as NOSPLIT this seems
+	// as though it could lead to situations where the linker's
+	// nosplit-overflow analysis would trigger a link failure. On the
+	// other hand if they not tagged NOSPLIT then this could cause
+	// problems when building the runtime (since there may be calls to
+	// asm routine in cases where it's not safe to grow the stack). In
+	// most cases the wrapper would be (in effect) inlined, but are
+	// there (perhaps) indirect calls from the runtime that could run
+	// into trouble here.
+	// FIXME: at the moment all.bash does not pass when I leave out
+	// NOSPLIT for these wrappers, so all are currently tagged with NOSPLIT.
+	fn.Pragma |= ir.Nosplit
+
+	// Generate call. Use tail call if no params and no returns,
+	// but a regular call otherwise.
+	//
+	// Note: ideally we would be using a tail call in cases where
+	// there are params but no returns for ABI0->ABIInternal wrappers,
+	// provided that all params fit into registers (e.g. we don't have
+	// to allocate any stack space). Doing this will require some
+	// extra work in typecheck/walk/ssa, might want to add a new node
+	// OTAILCALL or something to this effect.
+	tailcall := fn.Type().NumResults() == 0 && fn.Type().NumParams() == 0 && fn.Type().NumRecvs() == 0
+	if base.Ctxt.Arch.Name == "ppc64le" && base.Ctxt.Flag_dynlink {
+		// cannot tailcall on PPC64 with dynamic linking, as we need
+		// to restore R2 after call.
+		tailcall = false
+	}
+	if base.Ctxt.Arch.Name == "amd64" && wrapperABI == obj.ABIInternal {
+		// cannot tailcall from ABIInternal to ABI0 on AMD64, as we need
+		// to special registers (X15) when returning to ABIInternal.
+		tailcall = false
+	}
+
+	var tail ir.Node
+	call := ir.NewCallExpr(base.Pos, ir.OCALL, f.Nname, nil)
+	call.Args = ir.ParamNames(fn.Type())
+	call.IsDDD = fn.Type().IsVariadic()
+	tail = call
+	if tailcall {
+		tail = ir.NewTailCallStmt(base.Pos, call)
+	} else if fn.Type().NumResults() > 0 {
+		n := ir.NewReturnStmt(base.Pos, nil)
+		n.Results = []ir.Node{call}
+		tail = n
+	}
+	fn.Body.Append(tail)
+
+	typecheck.FinishFuncBody()
+	if base.Debug.DclStack != 0 {
+		types.CheckDclstack()
+	}
+
+	typecheck.Func(fn)
+	ir.CurFunc = fn
+	typecheck.Stmts(fn.Body)
+
+	typecheck.Target.Decls = append(typecheck.Target.Decls, fn)
+
+	// Restore previous context.
+	base.Pos = savepos
+	typecheck.DeclContext = savedclcontext
+	ir.CurFunc = savedcurfn
+}