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cmd/compile: fix defer/deferreturn

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Make sure we do any just-before-return cleanup on all paths out of a
function, including when recovering.  Each exit path should include
deferreturn (if there are any defers) and then the exit
code (e.g. copying heap-escaping return values back to the stack).

Introduce a Defer SSA block type which has two outgoing edges - one the
fallthrough edge (the defer was queued successfully) and one which
immediately returns (the defer had a successful recover() call and
normal execution should resume at the return point).

Fixes #14725

Change-Id: Iad035c9fd25ef8b7a74dafbd7461cf04833d981f
Reviewed-on: https://go-review.googlesource.com/20486
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Keith Randall 2016-03-09 19:27:57 -08:00
parent 9c8f549abb
commit ddc6b64444
9 changed files with 124 additions and 58 deletions
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6
src/cmd/compile/internal/ssa/regalloc.go
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@ -585,7 +585,7 @@ func (s *regAllocState) regalloc(f *Func) {
// Walk backwards through the block doing liveness analysis.
liveSet.clear()
d := int32(len(b.Values))
if b.Kind == BlockCall {
if b.Kind == BlockCall || b.Kind == BlockDefer {
d += unlikelyDistance
}
for _, e := range s.live[b.ID] {
@ -988,7 +988,7 @@ func (s *regAllocState) regalloc(f *Func) {
continue
}
for {
if p.Kind == BlockCall {
if p.Kind == BlockCall || p.Kind == BlockDefer {
goto badloop
}
if p == top {
@ -1607,7 +1607,7 @@ func (s *regAllocState) computeLive() {
// to beginning-of-block distance.
live.clear()
d := int32(len(b.Values))
if b.Kind == BlockCall {
if b.Kind == BlockCall || b.Kind == BlockDefer {
// Because we keep no values in registers across a call,
// make every use past a call very far away.
d += unlikelyDistance