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[dev.ssa] cmd/compile: small optimization to prove using sdom tweak

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Exposed data already in sdom to avoid recreating it in prove.

Change-Id: I834c9c03ed8faeaee013e5a1b3f955908f0e0915
Reviewed-on: https://go-review.googlesource.com/19999
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alexandru Moșoi <alexandru@mosoi.ro>
This commit is contained in:
David Chase 2016-02-28 15:58:17 -05:00
parent bdea1d58cf
commit 34f048c9d9
2 changed files with 19 additions and 11 deletions
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10
src/cmd/compile/internal/ssa/prove.go
View File

@ -127,14 +127,6 @@ var (
func prove(f *Func) {
idom := dominators(f)
sdom := newSparseTree(f, idom)
domTree := make([][]*Block, f.NumBlocks())
// Create a block ID -> [dominees] mapping
for _, b := range f.Blocks {
if dom := idom[b.ID]; dom != nil {
domTree[dom.ID] = append(domTree[dom.ID], b)
}
}
// current node state
type walkState int
@ -179,7 +171,7 @@ func prove(f *Func) {
saved: saved,
})
for _, s := range domTree[node.block.ID] {
for s := sdom.Child(node.block); s != nil; s = sdom.Sibling(s) {
work = append(work, bp{
block: s,
state: descend,

20
src/cmd/compile/internal/ssa/sparsetree.go
View File

@ -5,7 +5,6 @@
package ssa
type sparseTreeNode struct {
block *Block
child *Block
sibling *Block
parent *Block
@ -43,7 +42,6 @@ func newSparseTree(f *Func, parentOf []*Block) sparseTree {
t := make(sparseTree, f.NumBlocks())
for _, b := range f.Blocks {
n := &t[b.ID]
n.block = b
if p := parentOf[b.ID]; p != nil {
n.parent = p
n.sibling = t[p.ID].child
@ -98,6 +96,24 @@ func (t sparseTree) numberBlock(b *Block, n int32) int32 {
return n + 2
}
// Sibling returns a sibling of x in the dominator tree (i.e.,
// a node with the same immediate dominator) or nil if there
// are no remaining siblings in the arbitrary but repeatable
// order chosen. Because the Child-Sibling order is used
// to assign entry and exit numbers in the treewalk, those
// numbers are also consistent with this order (i.e.,
// Sibling(x) has entry number larger than x's exit number).
func (t sparseTree) Sibling(x *Block) *Block {
return t[x.ID].sibling
}
// Child returns a child of x in the dominator tree, or
// nil if there are none. The choice of first child is
// arbitrary but repeatable.
func (t sparseTree) Child(x *Block) *Block {
return t[x.ID].child
}
// isAncestorEq reports whether x is an ancestor of or equal to y.
func (t sparseTree) isAncestorEq(x, y *Block) bool {
xx := &t[x.ID]