[dev.ssa] cmd/compile: remember names of values
For debugging, spill values to named variables instead of autotmp_
variables if possible. We do this by keeping a name -> value map
for each function, keep it up-to-date during deadcode elim, and use
it to override spill decisions in stackalloc.
It might even make stack frames a bit smaller, as it makes it easy
to identify a set of spills which are likely not to interfere.
This just works for one-word variables for now. Strings/slices
will be a separate CL.
Change-Id: Ie89eba8cab16bcd41b311c479ec46dd7e64cdb67
Reviewed-on: https://go-review.googlesource.com/16336
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index f7100fe..c988465 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -304,14 +304,14 @@
var (
// dummy node for the memory variable
- memVar = Node{Op: ONAME, Sym: &Sym{Name: "mem"}}
+ memVar = Node{Op: ONAME, Class: Pxxx, Sym: &Sym{Name: "mem"}}
// dummy nodes for temporary variables
- ptrVar = Node{Op: ONAME, Sym: &Sym{Name: "ptr"}}
- capVar = Node{Op: ONAME, Sym: &Sym{Name: "cap"}}
- typVar = Node{Op: ONAME, Sym: &Sym{Name: "typ"}}
- idataVar = Node{Op: ONAME, Sym: &Sym{Name: "idata"}}
- okVar = Node{Op: ONAME, Sym: &Sym{Name: "ok"}}
+ ptrVar = Node{Op: ONAME, Class: Pxxx, Sym: &Sym{Name: "ptr"}}
+ capVar = Node{Op: ONAME, Class: Pxxx, Sym: &Sym{Name: "cap"}}
+ typVar = Node{Op: ONAME, Class: Pxxx, Sym: &Sym{Name: "typ"}}
+ idataVar = Node{Op: ONAME, Class: Pxxx, Sym: &Sym{Name: "idata"}}
+ okVar = Node{Op: ONAME, Class: Pxxx, Sym: &Sym{Name: "ok"}}
)
// startBlock sets the current block we're generating code in to b.
@@ -2021,6 +2021,7 @@
if left.Op == ONAME && canSSA(left) {
// Update variable assignment.
s.vars[left] = right
+ s.addNamedValue(left, right)
return
}
// not ssa-able. Treat as a store.
@@ -2245,13 +2246,14 @@
// If bounded is true then this address does not require a nil check for its operand
// even if that would otherwise be implied.
func (s *state) addr(n *Node, bounded bool) *ssa.Value {
+ t := Ptrto(n.Type)
switch n.Op {
case ONAME:
switch n.Class {
case PEXTERN:
// global variable
aux := &ssa.ExternSymbol{n.Type, n.Sym}
- v := s.entryNewValue1A(ssa.OpAddr, Ptrto(n.Type), aux, s.sb)
+ v := s.entryNewValue1A(ssa.OpAddr, t, aux, s.sb)
// TODO: Make OpAddr use AuxInt as well as Aux.
if n.Xoffset != 0 {
v = s.entryNewValue1I(ssa.OpOffPtr, v.Type, n.Xoffset, v)
@@ -2277,12 +2279,12 @@
// getting lucky. We might need a real dependency edge
// between vardef and addr ops.
aux := &ssa.AutoSymbol{Typ: n.Type, Node: n}
- return s.newValue1A(ssa.OpAddr, Ptrto(n.Type), aux, s.sp)
+ return s.newValue1A(ssa.OpAddr, t, aux, s.sp)
case PPARAMOUT: // Same as PAUTO -- cannot generate LEA early.
// ensure that we reuse symbols for out parameters so
// that cse works on their addresses
aux := s.lookupSymbol(n, &ssa.ArgSymbol{Typ: n.Type, Node: n})
- return s.newValue1A(ssa.OpAddr, Ptrto(n.Type), aux, s.sp)
+ return s.newValue1A(ssa.OpAddr, t, aux, s.sp)
case PAUTO | PHEAP, PPARAM | PHEAP, PPARAMOUT | PHEAP, PPARAMREF:
return s.expr(n.Name.Heapaddr)
default:
@@ -2296,18 +2298,18 @@
s.Unimplementedf("OINDREG of non-SP register %s in addr: %v", obj.Rconv(int(n.Reg)), n)
return nil
}
- return s.entryNewValue1I(ssa.OpOffPtr, Ptrto(n.Type), n.Xoffset, s.sp)
+ return s.entryNewValue1I(ssa.OpOffPtr, t, n.Xoffset, s.sp)
case OINDEX:
if n.Left.Type.IsSlice() {
a := s.expr(n.Left)
i := s.expr(n.Right)
i = s.extendIndex(i)
- len := s.newValue1(ssa.OpSliceLen, Types[TUINTPTR], a)
+ len := s.newValue1(ssa.OpSliceLen, Types[TINT], a)
if !n.Bounded {
s.boundsCheck(i, len)
}
- p := s.newValue1(ssa.OpSlicePtr, Ptrto(n.Left.Type.Type), a)
- return s.newValue2(ssa.OpPtrIndex, Ptrto(n.Left.Type.Type), p, i)
+ p := s.newValue1(ssa.OpSlicePtr, t, a)
+ return s.newValue2(ssa.OpPtrIndex, t, p, i)
} else { // array
a := s.addr(n.Left, bounded)
i := s.expr(n.Right)
@@ -2326,15 +2328,15 @@
return p
case ODOT:
p := s.addr(n.Left, bounded)
- return s.newValue2(ssa.OpAddPtr, p.Type, p, s.constIntPtr(Types[TUINTPTR], n.Xoffset))
+ return s.newValue2(ssa.OpAddPtr, t, p, s.constIntPtr(Types[TUINTPTR], n.Xoffset))
case ODOTPTR:
p := s.expr(n.Left)
if !bounded {
s.nilCheck(p)
}
- return s.newValue2(ssa.OpAddPtr, p.Type, p, s.constIntPtr(Types[TUINTPTR], n.Xoffset))
+ return s.newValue2(ssa.OpAddPtr, t, p, s.constIntPtr(Types[TUINTPTR], n.Xoffset))
case OCLOSUREVAR:
- return s.newValue2(ssa.OpAddPtr, Ptrto(n.Type),
+ return s.newValue2(ssa.OpAddPtr, t,
s.entryNewValue0(ssa.OpGetClosurePtr, Ptrto(Types[TUINT8])),
s.constIntPtr(Types[TUINTPTR], n.Xoffset))
case OPARAM:
@@ -2347,11 +2349,10 @@
original_p := *p
original_p.Xoffset = n.Xoffset
aux := &ssa.ArgSymbol{Typ: n.Type, Node: &original_p}
- return s.entryNewValue1A(ssa.OpAddr, Ptrto(n.Type), aux, s.sp)
+ return s.entryNewValue1A(ssa.OpAddr, t, aux, s.sp)
case OCONVNOP:
addr := s.addr(n.Left, bounded)
- to := Ptrto(n.Type)
- return s.newValue1(ssa.OpCopy, to, addr) // ensure that addr has the right type
+ return s.newValue1(ssa.OpCopy, t, addr) // ensure that addr has the right type
default:
s.Unimplementedf("unhandled addr %v", Oconv(int(n.Op), 0))
@@ -3155,6 +3156,7 @@
// need a phi value
v := b.NewValue0(s.peekLine(), ssa.OpPhi, t)
v.AddArgs(vals...)
+ s.addNamedValue(name, v)
return v
}
}
@@ -3182,6 +3184,33 @@
// TODO: the above mutually recursive functions can lead to very deep stacks. Fix that.
+func (s *state) addNamedValue(n *Node, v *ssa.Value) {
+ if n.Class == Pxxx {
+ // Don't track our dummy nodes (&memVar etc.).
+ return
+ }
+ if n.Sym == nil {
+ // TODO: What the heck is this?
+ return
+ }
+ if strings.HasPrefix(n.Sym.Name, "autotmp_") {
+ // Don't track autotmp_ variables.
+ return
+ }
+ if n.Class == PPARAM || n.Class == PPARAMOUT {
+ // TODO: Remove this
+ return
+ }
+ if n.Class == PAUTO && n.Xoffset != 0 {
+ s.Fatalf("AUTO var with offset %s %d", n, n.Xoffset)
+ }
+ values, ok := s.f.NamedValues[n]
+ if !ok {
+ s.f.Names = append(s.f.Names, n)
+ }
+ s.f.NamedValues[n] = append(values, v)
+}
+
// an unresolved branch
type branch struct {
p *obj.Prog // branch instruction
@@ -4441,7 +4470,7 @@
return &ssa.ExternSymbol{Typ: idealstring, Sym: data}
}
-func (e *ssaExport) Auto(t ssa.Type) fmt.Stringer {
+func (e *ssaExport) Auto(t ssa.Type) ssa.GCNode {
n := temp(t.(*Type)) // Note: adds new auto to Curfn.Func.Dcl list
e.mustImplement = true // This modifies the input to SSA, so we want to make sure we succeed from here!
return n
@@ -4480,3 +4509,7 @@
}
e.unimplemented = true
}
+
+func (n *Node) Typ() ssa.Type {
+ return n.Type
+}
