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cmd/compile: keep heap pointer for escaping output parameters live

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Make sure the pointer to the heap copy of an output parameter is kept
live throughout the function.  The function could panic at any point,
and then a defer could recover.  Thus, we need the pointer to the heap
copy always available so the post-deferreturn code can copy the return
value back to the stack.

Before this CL, the pointer to the heap copy could be considered dead in
certain situations, like code which is reverse dominated by a panic call.

Fixes #16095.

Change-Id: Ic3800423e563670e5b567b473bf4c84cddb49a4c
Reviewed-on: https://go-review.googlesource.com/24213
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Keith Randall 2016-06-18 19:40:57 -07:00
parent e96b1ef99b
commit 6effdd28de
4 changed files with 136 additions and 0 deletions
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12
src/cmd/compile/internal/gc/syntax.go
View file

@ -79,6 +79,7 @@ const (
hasBreak = 1 << iota
notLiveAtEnd
isClosureVar
isOutputParamHeapAddr
)
func (n *Node) HasBreak() bool {
@ -112,6 +113,17 @@ func (n *Node) setIsClosureVar(b bool) {
}
}
func (n *Node) IsOutputParamHeapAddr() bool {
return n.flags&isOutputParamHeapAddr != 0
}
func (n *Node) setIsOutputParamHeapAddr(b bool) {
if b {
n.flags |= isOutputParamHeapAddr
} else {
n.flags &^= isOutputParamHeapAddr
}
}
// Val returns the Val for the node.
func (n *Node) Val() Val {
if n.hasVal != +1 {