compiler, runtime: Use function descriptors.

This changes the representation of a Go value of function type
from being a pointer to function code (like a C function
pointer) to being a pointer to a struct.  The first field of
the struct points to the function code.  The remaining fields,
if any, are the addresses of variables referenced in enclosing
functions.  For each call to a function, the address of the
function descriptor is passed as the last argument.

This lets us avoid generating trampolines, and removes the use
of writable/executable sections of the heap.

From-SVN: r200181

2 files changed, 9 insertions, 3 deletions

diff --git a/libgo/go/runtime/extern.go b/libgo/go/runtime/extern.go
index 2a90113..6e91ef5 100644
--- a/libgo/go/runtime/extern.go
+++ b/libgo/go/runtime/extern.go
@@ -59,9 +59,6 @@ func (f *Func) FileLine(pc uintptr) (file string, line int) {
 // implemented in symtab.c
 func funcline_go(*Func, uintptr) (string, int)
 
-// mid returns the current OS thread (m) id.
-func mid() uint32
-
 // SetFinalizer sets the finalizer associated with x to f.
 // When the garbage collector finds an unreachable block
 // with an associated finalizer, it clears the association and runs
diff --git a/libgo/go/runtime/parfor_test.go b/libgo/go/runtime/parfor_test.go
index b382b76..4c69a68 100644
--- a/libgo/go/runtime/parfor_test.go
+++ b/libgo/go/runtime/parfor_test.go
@@ -13,6 +13,8 @@ import (
 	"unsafe"
 )
 
+var gdata []uint64
+
 // Simple serial sanity test for parallelfor.
 func TestParFor(t *testing.T) {
 	const P = 1
@@ -22,7 +24,12 @@ func TestParFor(t *testing.T) {
 		data[i] = i
 	}
 	desc := NewParFor(P)
+	// Avoid making func a closure: parfor cannot invoke them.
+	// Since it doesn't happen in the C code, it's not worth doing
+	// just for the test.
+	gdata = data
 	ParForSetup(desc, P, N, nil, true, func(desc *ParFor, i uint32) {
+		data := gdata
 		data[i] = data[i]*data[i] + 1
 	})
 	ParForDo(desc)
@@ -111,7 +118,9 @@ func TestParForParallel(t *testing.T) {
 	P := GOMAXPROCS(-1)
 	c := make(chan bool, P)
 	desc := NewParFor(uint32(P))
+	gdata = data
 	ParForSetup(desc, uint32(P), uint32(N), nil, false, func(desc *ParFor, i uint32) {
+		data := gdata
 		data[i] = data[i]*data[i] + 1
 	})
 	for p := 1; p < P; p++ {