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cmd/compile: in poset, refactor aliasnode

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In preparation for allowing to make multiple nodes as aliases
in a single pass, refactor aliasnode splitting out the case
in which one of the nodes is not in the post into a new
funciton (aliasnewnode).

No functional changes, passes toolstash -cmp

Change-Id: I19ca6ef8426f8aec9f2622b6151c5c617dbb25b5
Reviewed-on: https://go-review.googlesource.com/c/go/+/200859
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Giovanni Bajo 2019-09-28 00:08:45 +02:00
parent c3e8a20a65
commit 7e68f81dd8
1 changed files with 48 additions and 40 deletions
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88
src/cmd/compile/internal/ssa/poset.go
View file

@ -407,7 +407,19 @@ func (po *poset) newconst(n *Value) {
po.upushconst(i, 0)
}
// aliasnode records that n2 is an alias of n1
// aliasnewnode records that a single node n2 (not in the poset yet) is an alias
// of the master node n1.
func (po *poset) aliasnewnode(n1, n2 *Value) {
i1, i2 := po.values[n1.ID], po.values[n2.ID]
if i1 == 0 || i2 != 0 {
panic("aliasnewnode invalid arguments")
}
po.values[n2.ID] = i1
po.upushalias(n2.ID, 0)
}
// aliasnode records that n2 (already in the poset) is an alias of n1
func (po *poset) aliasnode(n1, n2 *Value) {
i1 := po.values[n1.ID]
if i1 == 0 {
@ -415,48 +427,44 @@ func (po *poset) aliasnode(n1, n2 *Value) {
}
i2 := po.values[n2.ID]
if i2 != 0 {
// Rename all references to i2 into i1
// (do not touch i1 itself, otherwise we can create useless self-loops)
for idx, n := range po.nodes {
if uint32(idx) != i1 {
l, r := n.l, n.r
if l.Target() == i2 {
po.setchl(uint32(idx), newedge(i1, l.Strict()))
po.upush(undoSetChl, uint32(idx), l)
}
if r.Target() == i2 {
po.setchr(uint32(idx), newedge(i1, r.Strict()))
po.upush(undoSetChr, uint32(idx), r)
}
if i2 == 0 {
panic("aliasnode for non-existing node")
}
// Rename all references to i2 into i1
// (do not touch i1 itself, otherwise we can create useless self-loops)
for idx, n := range po.nodes {
if uint32(idx) != i1 {
l, r := n.l, n.r
if l.Target() == i2 {
po.setchl(uint32(idx), newedge(i1, l.Strict()))
po.upush(undoSetChl, uint32(idx), l)
}
if r.Target() == i2 {
po.setchr(uint32(idx), newedge(i1, r.Strict()))
po.upush(undoSetChr, uint32(idx), r)
}
}
}
// Reassign all existing IDs that point to i2 to i1.
// This includes n2.ID.
for k, v := range po.values {
if v == i2 {
po.values[k] = i1
po.upushalias(k, i2)
}
// Reassign all existing IDs that point to i2 to i1.
// This includes n2.ID.
for k, v := range po.values {
if v == i2 {
po.values[k] = i1
po.upushalias(k, i2)
}
}
if n2.isGenericIntConst() {
val := n2.AuxInt
if po.flags&posetFlagUnsigned != 0 {
val = int64(n2.AuxUnsigned())
}
if po.constants[val] != i2 {
panic("aliasing constant which is not registered")
}
po.constants[val] = i1
po.upushconst(i1, i2)
if n2.isGenericIntConst() {
val := n2.AuxInt
if po.flags&posetFlagUnsigned != 0 {
val = int64(n2.AuxUnsigned())
}
} else {
// n2.ID wasn't seen before, so record it as alias to i1
po.values[n2.ID] = i1
po.upushalias(n2.ID, 0)
if po.constants[val] != i2 {
panic("aliasing constant which is not registered")
}
po.constants[val] = i1
po.upushconst(i1, i2)
}
}
@ -1093,11 +1101,11 @@ func (po *poset) SetEqual(n1, n2 *Value) bool {
i1 = po.newnode(n1)
po.roots = append(po.roots, i1)
po.upush(undoNewRoot, i1, 0)
po.aliasnode(n1, n2)
po.aliasnewnode(n1, n2)
case f1 && !f2:
po.aliasnode(n1, n2)
po.aliasnewnode(n1, n2)
case !f1 && f2:
po.aliasnode(n2, n1)
po.aliasnewnode(n2, n1)
case f1 && f2:
if i1 == i2 {
// Already aliased, ignore