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// 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.
// Portable half of code generator; mainly statements and control flow.
package gc
import "fmt"
func Sysfunc(name string) *Node {
n := newname(Pkglookup(name, Runtimepkg))
n.Class = PFUNC
return n
}
// addrescapes tags node n as having had its address taken
// by "increasing" the "value" of n.Esc to EscHeap.
// Storage is allocated as necessary to allow the address
// to be taken.
func addrescapes(n *Node) {
switch n.Op {
// probably a type error already.
// dump("addrescapes", n);
default:
break
case ONAME:
if n == nodfp {
break
}
// if this is a tmpname (PAUTO), it was tagged by tmpname as not escaping.
// on PPARAM it means something different.
if n.Class == PAUTO && n.Esc == EscNever {
break
}
// If a closure reference escapes, mark the outer variable as escaping.
if n.isClosureVar() {
addrescapes(n.Name.Defn)
break
}
if n.Class != PPARAM && n.Class != PPARAMOUT && n.Class != PAUTO {
break
}
// This is a plain parameter or local variable that needs to move to the heap,
// but possibly for the function outside the one we're compiling.
// That is, if we have:
//
// func f(x int) {
// func() {
// global = &x
// }
// }
//
// then we're analyzing the inner closure but we need to move x to the
// heap in f, not in the inner closure. Flip over to f before calling moveToHeap.
oldfn := Curfn
Curfn = n.Name.Curfn
if Curfn.Func.Closure != nil && Curfn.Op == OCLOSURE {
Curfn = Curfn.Func.Closure
}
ln := lineno
lineno = Curfn.Pos
moveToHeap(n)
Curfn = oldfn
lineno = ln
case OIND, ODOTPTR:
break
// ODOTPTR has already been introduced,
// so these are the non-pointer ODOT and OINDEX.
// In &x[0], if x is a slice, then x does not
// escape--the pointer inside x does, but that
// is always a heap pointer anyway.
case ODOT, OINDEX, OPAREN, OCONVNOP:
if !n.Left.Type.IsSlice() {
addrescapes(n.Left)
}
}
}
// isParamStackCopy reports whether this is the on-stack copy of a
// function parameter that moved to the heap.
func (n *Node) isParamStackCopy() bool {
return n.Op == ONAME && (n.Class == PPARAM || n.Class == PPARAMOUT) && n.Name.Heapaddr != nil
}
// isParamHeapCopy reports whether this is the on-heap copy of
// a function parameter that moved to the heap.
func (n *Node) isParamHeapCopy() bool {
return n.Op == ONAME && n.Class == PAUTOHEAP && n.Name.Param.Stackcopy != nil
}
// moveToHeap records the parameter or local variable n as moved to the heap.
func moveToHeap(n *Node) {
if Debug['r'] != 0 {
Dump("MOVE", n)
}
if compiling_runtime {
yyerror("%v escapes to heap, not allowed in runtime.", n)
}
if n.Class == PAUTOHEAP {
Dump("n", n)
Fatalf("double move to heap")
}
// Allocate a local stack variable to hold the pointer to the heap copy.
// temp will add it to the function declaration list automatically.
heapaddr := temp(ptrto(n.Type))
heapaddr.Sym = lookup("&" + n.Sym.Name)
heapaddr.Orig.Sym = heapaddr.Sym
// Unset AutoTemp to persist the &foo variable name through SSA to
// liveness analysis.
// TODO(mdempsky/drchase): Cleaner solution?
heapaddr.Name.AutoTemp = false
// Parameters have a local stack copy used at function start/end
// in addition to the copy in the heap that may live longer than
// the function.
if n.Class == PPARAM || n.Class == PPARAMOUT {
if n.Xoffset == BADWIDTH {
Fatalf("addrescapes before param assignment")
}
// We rewrite n below to be a heap variable (indirection of heapaddr).
// Preserve a copy so we can still write code referring to the original,
// and substitute that copy into the function declaration list
// so that analyses of the local (on-stack) variables use it.
stackcopy := nod(ONAME, nil, nil)
stackcopy.Sym = n.Sym
stackcopy.Type = n.Type
stackcopy.Xoffset = n.Xoffset
stackcopy.Class = n.Class
stackcopy.Name.Heapaddr = heapaddr
if n.Class == PPARAMOUT {
// Make sure the pointer to the heap copy is kept live throughout the function.
// The function could panic at any point, and then a defer could recover.
// Thus, we need the pointer to the heap copy always available so the
// post-deferreturn code can copy the return value back to the stack.
// See issue 16095.
heapaddr.setIsOutputParamHeapAddr(true)
}
n.Name.Param.Stackcopy = stackcopy
// Substitute the stackcopy into the function variable list so that
// liveness and other analyses use the underlying stack slot
// and not the now-pseudo-variable n.
found := false
for i, d := range Curfn.Func.Dcl {
if d == n {
Curfn.Func.Dcl[i] = stackcopy
found = true
break
}
// Parameters are before locals, so can stop early.
// This limits the search even in functions with many local variables.
if d.Class == PAUTO {
break
}
}
if !found {
Fatalf("cannot find %v in local variable list", n)
}
Curfn.Func.Dcl = append(Curfn.Func.Dcl, n)
}
// Modify n in place so that uses of n now mean indirection of the heapaddr.
n.Class = PAUTOHEAP
n.Ullman = 2
n.Xoffset = 0
n.Name.Heapaddr = heapaddr
n.Esc = EscHeap
if Debug['m'] != 0 {
fmt.Printf("%v: moved to heap: %v\n", n.Line(), n)
}
}
// make a new Node off the books
func tempname(nn *Node, t *Type) {
if Curfn == nil {
Fatalf("no curfn for tempname")
}
if Curfn.Func.Closure != nil && Curfn.Op == OCLOSURE {
Dump("tempname", Curfn)
Fatalf("adding tempname to wrong closure function")
}
if t == nil {
yyerror("tempname called with nil type")
t = Types[TINT32]
}
// give each tmp a different name so that there
// a chance to registerizer them.
// Add a preceding . to avoid clash with legal names.
s := lookupN(".autotmp_", statuniqgen)
statuniqgen++
n := nod(ONAME, nil, nil)
n.Sym = s
s.Def = n
n.Type = t
n.Class = PAUTO
n.Addable = true
n.Ullman = 1
n.Esc = EscNever
n.Name.Curfn = Curfn
n.Name.AutoTemp = true
Curfn.Func.Dcl = append(Curfn.Func.Dcl, n)
dowidth(t)
n.Xoffset = 0
*nn = *n
}
func temp(t *Type) *Node {
var n Node
tempname(&n, t)
n.Sym.Def.Used = true
return n.Orig
}
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