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cmd/compile: CSE copied tuple selectors

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In CSE if a tuple generator is CSE'd to a different block, its
selectors are copied to the same block. In this case, also CES
the copied selectors.

Test copied from Keith's CL 27202.

Fixes #16741.

Change-Id: I2fc8b9513d430f10d6104275cfff5fb75d3ef3d9
Reviewed-on: https://go-review.googlesource.com/27236
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Cherry Zhang 2016-08-17 13:29:19 -04:00
parent 2b8e143dc3
commit 3d5cf72ca9
2 changed files with 28 additions and 0 deletions
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11
src/cmd/compile/internal/ssa/cse.go
View file

@ -166,7 +166,10 @@ func cse(f *Func) {
// if we rewrite a tuple generator to a new one in a different block,
// copy its selectors to the new generator's block, so tuple generator
// and selectors stay together.
// be careful not to copy same selectors more than once (issue 16741).
copiedSelects := make(map[ID][]*Value)
for _, b := range f.Blocks {
out:
for _, v := range b.Values {
if rewrite[v.ID] != nil {
continue
@ -180,8 +183,16 @@ func cse(f *Func) {
t := rewrite[v.Args[0].ID]
if t != nil && t.Block != b {
// v.Args[0] is tuple generator, CSE'd into a different block as t, v is left behind
for _, c := range copiedSelects[t.ID] {
if v.Op == c.Op {
// an equivalent selector is already copied
rewrite[v.ID] = c
continue out
}
}
c := v.copyInto(t.Block)
rewrite[v.ID] = c
copiedSelects[t.ID] = append(copiedSelects[t.ID], c)
}
}
}