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cmd/compile: don't spill rematerializeable value when resolving merge edges

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Fixes #19515.

Change-Id: I4bcce152cef52d00fbb5ab4daf72a6e742bae27c
Reviewed-on: https://go-review.googlesource.com/38158
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Cherry Zhang 2017-03-14 18:21:23 -04:00
parent 2d78538c12
commit 8a44c8efae
2 changed files with 58 additions and 4 deletions
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11
src/cmd/compile/internal/ssa/regalloc.go
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@ -2227,6 +2227,7 @@ func (e *edgeState) findRegFor(typ Type) Location {
// 1) an unused register
// 2) a non-unique register not holding a final value
// 3) a non-unique register
// 4) TODO: a register holding a rematerializeable value
x := m &^ e.usedRegs
if x != 0 {
return &e.s.registers[pickReg(x)]
@ -2252,10 +2253,12 @@ func (e *edgeState) findRegFor(typ Type) Location {
a := e.cache[vid]
for _, c := range a {
if r, ok := e.s.f.getHome(c.ID).(*Register); ok && m>>uint(r.num)&1 != 0 {
x := e.p.NewValue1(c.Pos, OpStoreReg, c.Type, c)
e.set(t, vid, x, false, c.Pos)
if e.s.f.pass.debug > regDebug {
fmt.Printf(" SPILL %s->%s %s\n", r.Name(), t.Name(), x.LongString())
if !c.rematerializeable() {
x := e.p.NewValue1(c.Pos, OpStoreReg, c.Type, c)
e.set(t, vid, x, false, c.Pos)
if e.s.f.pass.debug > regDebug {
fmt.Printf(" SPILL %s->%s %s\n", r.Name(), t.Name(), x.LongString())
}
}
// r will now be overwritten by the caller. At some point
// later, the newly saved value will be moved back to its