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cmd/compile: in prove, give a different name to each poset

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Instead of using a two-slot array and having to remember which
index is the signed poset, and which is the unsigned one, just
use two different variables.

Change-Id: Ic7f7676436c51bf43a182e999a926f8b7f69434b
Reviewed-on: https://go-review.googlesource.com/c/go/+/196678
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Giovanni Bajo 2019-09-20 00:12:15 +02:00
parent e4c3925925
commit b16463c912
1 changed files with 21 additions and 19 deletions
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40
src/cmd/compile/internal/ssa/prove.go
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@ -164,7 +164,8 @@ type factsTable struct {
// order is a couple of partial order sets that record information
// about relations between SSA values in the signed and unsigned
// domain.
order [2]*poset
orderS *poset
orderU *poset
// known lower and upper bounds on individual values.
limits map[ID]limit
@ -187,10 +188,10 @@ var checkpointBound = limitFact{}
func newFactsTable(f *Func) *factsTable {
ft := &factsTable{}
ft.order[0] = f.newPoset() // signed
ft.order[1] = f.newPoset() // unsigned
ft.order[0].SetUnsigned(false)
ft.order[1].SetUnsigned(true)
ft.orderS = f.newPoset()
ft.orderU = f.newPoset()
ft.orderS.SetUnsigned(false)
ft.orderU.SetUnsigned(true)
ft.facts = make(map[pair]relation)
ft.stack = make([]fact, 4)
ft.limits = make(map[ID]limit)
@ -221,23 +222,23 @@ func (ft *factsTable) update(parent *Block, v, w *Value, d domain, r relation) {
if d == signed || d == unsigned {
var ok bool
idx := 0
order := ft.orderS
if d == unsigned {
idx = 1
order = ft.orderU
}
switch r {
case lt:
ok = ft.order[idx].SetOrder(v, w)
ok = order.SetOrder(v, w)
case gt:
ok = ft.order[idx].SetOrder(w, v)
ok = order.SetOrder(w, v)
case lt | eq:
ok = ft.order[idx].SetOrderOrEqual(v, w)
ok = order.SetOrderOrEqual(v, w)
case gt | eq:
ok = ft.order[idx].SetOrderOrEqual(w, v)
ok = order.SetOrderOrEqual(w, v)
case eq:
ok = ft.order[idx].SetEqual(v, w)
ok = order.SetEqual(v, w)
case lt | gt:
ok = ft.order[idx].SetNonEqual(v, w)
ok = order.SetNonEqual(v, w)
default:
panic("unknown relation")
}
@ -588,6 +589,7 @@ func (ft *factsTable) isNonNegative(v *Value) bool {
}
// Check if the recorded limits can prove that the value is positive
if l, has := ft.limits[v.ID]; has && (l.min >= 0 || l.umax <= uint64(max)) {
return true
}
@ -610,7 +612,7 @@ func (ft *factsTable) isNonNegative(v *Value) bool {
}
// Check if the signed poset can prove that the value is >= 0
return ft.order[0].OrderedOrEqual(ft.zero, v)
return ft.orderS.OrderedOrEqual(ft.zero, v)
}
// checkpoint saves the current state of known relations.
@ -621,8 +623,8 @@ func (ft *factsTable) checkpoint() {
}
ft.stack = append(ft.stack, checkpointFact)
ft.limitStack = append(ft.limitStack, checkpointBound)
ft.order[0].Checkpoint()
ft.order[1].Checkpoint()
ft.orderS.Checkpoint()
ft.orderU.Checkpoint()
}
// restore restores known relation to the state just
@ -658,8 +660,8 @@ func (ft *factsTable) restore() {
ft.limits[old.vid] = old.limit
}
}
ft.order[0].Undo()
ft.order[1].Undo()
ft.orderS.Undo()
ft.orderU.Undo()
}
func lessByID(v, w *Value) bool {
@ -922,7 +924,7 @@ func prove(f *Func) {
ft.restore()
// Return the posets to the free list
for _, po := range ft.order {
for _, po := range []*poset{ft.orderS, ft.orderU} {
// Make sure it's empty as it should be. A non-empty poset
// might cause errors and miscompilations if reused.
if checkEnabled {