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cmd/compile: improve undo of poset

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prove uses the poset datastructure in a DFS walk, and always undoes
it back to its pristine status. Before this CL, poset's undo of
a new node creation didn't fully deallocate the node, which means
that at the end of prove there was still some allocated memory pending.

This was not a problem until now because the posets used by prove
were discarded after each function, but it would prevent recycling
them between functions (as a followup CL does).

Change-Id: I1c1c99c03fe19ad765395a43958cb256f686765a
Reviewed-on: https://go-review.googlesource.com/112976
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Giovanni Bajo 2018-05-12 22:13:44 +02:00 • committed by David Chase
parent 7bac2a95f6
commit 67656ba71b
3 changed files with 20 additions and 10 deletions
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26
src/cmd/compile/internal/ssa/poset.go
View file

@ -679,13 +679,24 @@ func (po *poset) CheckIntegrity() (err error) {
// It can be used for debugging purposes, as a poset is supposed to
// be empty after it's fully rolled back through Undo.
func (po *poset) CheckEmpty() error {
// Check that the poset is completely empty
if len(po.nodes) != 1 {
return fmt.Errorf("non-empty nodes list: %v", po.nodes)
}
if len(po.values) != 0 {
return fmt.Errorf("non-empty value map: %v", po.values)
}
if len(po.roots) != 0 {
return fmt.Errorf("non-empty root list: %v", po.roots)
}
if len(po.constants) != 0 {
return fmt.Errorf("non-empty constants: %v", po.constants)
}
if len(po.undo) != 0 {
return fmt.Errorf("non-empty undo list: %v", po.undo)
}
if po.lastidx != 0 {
return fmt.Errorf("lastidx index is not zero: %v", po.lastidx)
}
for _, bs := range po.noneq {
for _, x := range bs {
if x != 0 {
@ -693,14 +704,6 @@ func (po *poset) CheckEmpty() error {
}
}
}
for idx, n := range po.nodes {
if n.l|n.r != 0 {
return fmt.Errorf("non-empty node %v->[%d,%d]", idx, n.l.Target(), n.r.Target())
}
}
if len(po.constants) != 0 {
return fmt.Errorf("non-empty constant")
}
return nil
}
@ -1123,6 +1126,9 @@ func (po *poset) Undo() {
po.noneq[pass.ID].Clear(pass.idx)
case undoNewNode:
if pass.idx != po.lastidx {
panic("invalid newnode index")
}
if pass.ID != 0 {
if po.values[pass.ID] != pass.idx {
panic("invalid newnode undo pass")
@ -1131,6 +1137,8 @@ func (po *poset) Undo() {
}
po.setchl(pass.idx, 0)
po.setchr(pass.idx, 0)
po.nodes = po.nodes[:pass.idx]
po.lastidx--
// If it was the last inserted constant, remove it
nc := len(po.constants)