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[dev.ssa] Protect control value from being moved away from end of block

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If there isn't a value dependency between the control value of a
block and some other value, the schedule pass might move the control
value to a spot that is not EOB. Fix by handling the control value
specially like phis.

Change-Id: Iddaf0924d98c5b3d9515c3ced927b0c85722818c
Reviewed-on: https://go-review.googlesource.com/11071
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Daniel Morsing 2015-06-13 19:27:26 +01:00
parent 8f22b5292f
commit 2efdaefdb0
1 changed files with 8 additions and 2 deletions
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10
src/cmd/compile/internal/ssa/schedule.go
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@ -57,6 +57,9 @@ func schedule(f *Func) {
// Topologically sort the values in b.
order = order[:0]
for _, v := range b.Values {
if v == b.Control {
continue
}
if v.Op == OpPhi {
// Phis all go first. We handle phis specially
// because they may have self edges "a = phi(a, b, c)"
@ -79,13 +82,13 @@ func schedule(f *Func) {
// Note that v is not popped. We leave it in place
// until all its children have been explored.
for _, w := range v.Args {
if w.Block == b && w.Op != OpPhi && state[w.ID] == unmarked {
if w.Block == b && w.Op != OpPhi && w != b.Control && state[w.ID] == unmarked {
state[w.ID] = found
queue = append(queue, w)
}
}
for _, w := range additionalEdges[v.ID] {
if w.Block == b && w.Op != OpPhi && state[w.ID] == unmarked {
if w.Block == b && w.Op != OpPhi && w != b.Control && state[w.ID] == unmarked {
state[w.ID] = found
queue = append(queue, w)
}
@ -99,6 +102,9 @@ func schedule(f *Func) {
}
}
}
if b.Control != nil {
order = append(order, b.Control)
}
copy(b.Values, order)
}
// TODO: only allow one live flags type (x86)