libgo, compiler: Upgrade libgo to Go 1.4, except for runtime.

This upgrades all of libgo other than the runtime package to
the Go 1.4 release.  In Go 1.4 much of the runtime was
rewritten into Go.  Merging that code will take more time and
will not change the API, so I'm putting it off for now.

There are a few runtime changes anyhow, to accomodate other
packages that rely on minor modifications to the runtime
support.

The compiler changes slightly to add a one-bit flag to each
type descriptor kind that is stored directly in an interface,
which for gccgo is currently only pointer types.  Another
one-bit flag (gcprog) is reserved because it is used by the gc
compiler, but gccgo does not currently use it.

There is another error check in the compiler since I ran
across it during testing.

gotools/:
	* Makefile.am (go_cmd_go_files): Sort entries.  Add generate.go.
	* Makefile.in: Rebuild.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@219627 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 279 insertions, 0 deletions

diff --git a/libgo/go/runtime/cgocall.go b/libgo/go/runtime/cgocall.go
new file mode 100644
index 00000000000..7fd91469eb1
--- /dev/null
+++ b/libgo/go/runtime/cgocall.go
@@ -0,0 +1,279 @@
+// 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.
+
+// Cgo call and callback support.
+//
+// To call into the C function f from Go, the cgo-generated code calls
+// runtime.cgocall(_cgo_Cfunc_f, frame), where _cgo_Cfunc_f is a
+// gcc-compiled function written by cgo.
+//
+// runtime.cgocall (below) locks g to m, calls entersyscall
+// so as not to block other goroutines or the garbage collector,
+// and then calls runtime.asmcgocall(_cgo_Cfunc_f, frame).
+//
+// runtime.asmcgocall (in asm_$GOARCH.s) switches to the m->g0 stack
+// (assumed to be an operating system-allocated stack, so safe to run
+// gcc-compiled code on) and calls _cgo_Cfunc_f(frame).
+//
+// _cgo_Cfunc_f invokes the actual C function f with arguments
+// taken from the frame structure, records the results in the frame,
+// and returns to runtime.asmcgocall.
+//
+// After it regains control, runtime.asmcgocall switches back to the
+// original g (m->curg)'s stack and returns to runtime.cgocall.
+//
+// After it regains control, runtime.cgocall calls exitsyscall, which blocks
+// until this m can run Go code without violating the $GOMAXPROCS limit,
+// and then unlocks g from m.
+//
+// The above description skipped over the possibility of the gcc-compiled
+// function f calling back into Go.  If that happens, we continue down
+// the rabbit hole during the execution of f.
+//
+// To make it possible for gcc-compiled C code to call a Go function p.GoF,
+// cgo writes a gcc-compiled function named GoF (not p.GoF, since gcc doesn't
+// know about packages).  The gcc-compiled C function f calls GoF.
+//
+// GoF calls crosscall2(_cgoexp_GoF, frame, framesize).  Crosscall2
+// (in cgo/gcc_$GOARCH.S, a gcc-compiled assembly file) is a two-argument
+// adapter from the gcc function call ABI to the 6c function call ABI.
+// It is called from gcc to call 6c functions.  In this case it calls
+// _cgoexp_GoF(frame, framesize), still running on m->g0's stack
+// and outside the $GOMAXPROCS limit.  Thus, this code cannot yet
+// call arbitrary Go code directly and must be careful not to allocate
+// memory or use up m->g0's stack.
+//
+// _cgoexp_GoF calls runtime.cgocallback(p.GoF, frame, framesize).
+// (The reason for having _cgoexp_GoF instead of writing a crosscall3
+// to make this call directly is that _cgoexp_GoF, because it is compiled
+// with 6c instead of gcc, can refer to dotted names like
+// runtime.cgocallback and p.GoF.)
+//
+// runtime.cgocallback (in asm_$GOARCH.s) switches from m->g0's
+// stack to the original g (m->curg)'s stack, on which it calls
+// runtime.cgocallbackg(p.GoF, frame, framesize).
+// As part of the stack switch, runtime.cgocallback saves the current
+// SP as m->g0->sched.sp, so that any use of m->g0's stack during the
+// execution of the callback will be done below the existing stack frames.
+// Before overwriting m->g0->sched.sp, it pushes the old value on the
+// m->g0 stack, so that it can be restored later.
+//
+// runtime.cgocallbackg (below) is now running on a real goroutine
+// stack (not an m->g0 stack).  First it calls runtime.exitsyscall, which will
+// block until the $GOMAXPROCS limit allows running this goroutine.
+// Once exitsyscall has returned, it is safe to do things like call the memory
+// allocator or invoke the Go callback function p.GoF.  runtime.cgocallbackg
+// first defers a function to unwind m->g0.sched.sp, so that if p.GoF
+// panics, m->g0.sched.sp will be restored to its old value: the m->g0 stack
+// and the m->curg stack will be unwound in lock step.
+// Then it calls p.GoF.  Finally it pops but does not execute the deferred
+// function, calls runtime.entersyscall, and returns to runtime.cgocallback.
+//
+// After it regains control, runtime.cgocallback switches back to
+// m->g0's stack (the pointer is still in m->g0.sched.sp), restores the old
+// m->g0.sched.sp value from the stack, and returns to _cgoexp_GoF.
+//
+// _cgoexp_GoF immediately returns to crosscall2, which restores the
+// callee-save registers for gcc and returns to GoF, which returns to f.
+
+package runtime
+
+import "unsafe"
+
+// Call from Go to C.
+//go:nosplit
+func cgocall(fn, arg unsafe.Pointer) {
+	cgocall_errno(fn, arg)
+}
+
+//go:nosplit
+func cgocall_errno(fn, arg unsafe.Pointer) int32 {
+	if !iscgo && GOOS != "solaris" && GOOS != "windows" {
+		gothrow("cgocall unavailable")
+	}
+
+	if fn == nil {
+		gothrow("cgocall nil")
+	}
+
+	if raceenabled {
+		racereleasemerge(unsafe.Pointer(&racecgosync))
+	}
+
+	// Create an extra M for callbacks on threads not created by Go on first cgo call.
+	if needextram == 1 && cas(&needextram, 1, 0) {
+		onM(newextram)
+	}
+
+	/*
+	 * Lock g to m to ensure we stay on the same stack if we do a
+	 * cgo callback. Add entry to defer stack in case of panic.
+	 */
+	lockOSThread()
+	mp := getg().m
+	mp.ncgocall++
+	mp.ncgo++
+	defer endcgo(mp)
+
+	/*
+	 * Announce we are entering a system call
+	 * so that the scheduler knows to create another
+	 * M to run goroutines while we are in the
+	 * foreign code.
+	 *
+	 * The call to asmcgocall is guaranteed not to
+	 * split the stack and does not allocate memory,
+	 * so it is safe to call while "in a system call", outside
+	 * the $GOMAXPROCS accounting.
+	 */
+	entersyscall()
+	errno := asmcgocall_errno(fn, arg)
+	exitsyscall()
+
+	return errno
+}
+
+//go:nosplit
+func endcgo(mp *m) {
+	mp.ncgo--
+	if mp.ncgo == 0 {
+		// We are going back to Go and are not in a recursive
+		// call.  Let the GC collect any memory allocated via
+		// _cgo_allocate that is no longer referenced.
+		mp.cgomal = nil
+	}
+
+	if raceenabled {
+		raceacquire(unsafe.Pointer(&racecgosync))
+	}
+
+	unlockOSThread() // invalidates mp
+}
+
+// Helper functions for cgo code.
+
+// Filled by schedinit from corresponding C variables,
+// which are in turn filled in by dynamic linker when Cgo is available.
+var cgoMalloc, cgoFree unsafe.Pointer
+
+func cmalloc(n uintptr) unsafe.Pointer {
+	var args struct {
+		n   uint64
+		ret unsafe.Pointer
+	}
+	args.n = uint64(n)
+	cgocall(cgoMalloc, unsafe.Pointer(&args))
+	if args.ret == nil {
+		gothrow("C malloc failed")
+	}
+	return args.ret
+}
+
+func cfree(p unsafe.Pointer) {
+	cgocall(cgoFree, p)
+}
+
+// Call from C back to Go.
+//go:nosplit
+func cgocallbackg() {
+	gp := getg()
+	if gp != gp.m.curg {
+		println("runtime: bad g in cgocallback")
+		exit(2)
+	}
+
+	// entersyscall saves the caller's SP to allow the GC to trace the Go
+	// stack. However, since we're returning to an earlier stack frame and
+	// need to pair with the entersyscall() call made by cgocall, we must
+	// save syscall* and let reentersyscall restore them.
+	savedsp := unsafe.Pointer(gp.syscallsp)
+	savedpc := gp.syscallpc
+	exitsyscall() // coming out of cgo call
+	cgocallbackg1()
+	// going back to cgo call
+	reentersyscall(savedpc, savedsp)
+}
+
+func cgocallbackg1() {
+	gp := getg()
+	if gp.m.needextram {
+		gp.m.needextram = false
+		onM(newextram)
+	}
+
+	// Add entry to defer stack in case of panic.
+	restore := true
+	defer unwindm(&restore)
+
+	if raceenabled {
+		raceacquire(unsafe.Pointer(&racecgosync))
+	}
+
+	type args struct {
+		fn      *funcval
+		arg     unsafe.Pointer
+		argsize uintptr
+	}
+	var cb *args
+
+	// Location of callback arguments depends on stack frame layout
+	// and size of stack frame of cgocallback_gofunc.
+	sp := gp.m.g0.sched.sp
+	switch GOARCH {
+	default:
+		gothrow("cgocallbackg is unimplemented on arch")
+	case "arm":
+		// On arm, stack frame is two words and there's a saved LR between
+		// SP and the stack frame and between the stack frame and the arguments.
+		cb = (*args)(unsafe.Pointer(sp + 4*ptrSize))
+	case "amd64":
+		// On amd64, stack frame is one word, plus caller PC.
+		cb = (*args)(unsafe.Pointer(sp + 2*ptrSize))
+	case "386":
+		// On 386, stack frame is three words, plus caller PC.
+		cb = (*args)(unsafe.Pointer(sp + 4*ptrSize))
+	}
+
+	// Invoke callback.
+	reflectcall(unsafe.Pointer(cb.fn), unsafe.Pointer(cb.arg), uint32(cb.argsize), 0)
+
+	if raceenabled {
+		racereleasemerge(unsafe.Pointer(&racecgosync))
+	}
+
+	// Do not unwind m->g0->sched.sp.
+	// Our caller, cgocallback, will do that.
+	restore = false
+}
+
+func unwindm(restore *bool) {
+	if !*restore {
+		return
+	}
+	// Restore sp saved by cgocallback during
+	// unwind of g's stack (see comment at top of file).
+	mp := acquirem()
+	sched := &mp.g0.sched
+	switch GOARCH {
+	default:
+		gothrow("unwindm not implemented")
+	case "386", "amd64":
+		sched.sp = *(*uintptr)(unsafe.Pointer(sched.sp))
+	case "arm":
+		sched.sp = *(*uintptr)(unsafe.Pointer(sched.sp + 4))
+	}
+	releasem(mp)
+}
+
+// called from assembly
+func badcgocallback() {
+	gothrow("misaligned stack in cgocallback")
+}
+
+// called from (incomplete) assembly
+func cgounimpl() {
+	gothrow("cgo not implemented")
+}
+
+var racecgosync uint64 // represents possible synchronization in C code