runtime: avoid write barriers when calling deferred function
Calling a deferred function currently requires changing from a uintptr to the function code to a Go function value. That is done by setting the value of a func local variable using unsafe.Pointer. The local variable will always be on the stack. Adjust the code that sets the local variable to avoid generating a write barrier. A write barrier is never needed here. Also, for deferreturn, we must avoid write barriers entirely when called from a cgo function; that requires more than just this, but this is a start. The test for this is runtime tests that use the go tool; these are not currently run, but they will be in the future. Reviewed-on: https://go-review.googlesource.com/46455 From-SVN: r249559
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@ -1,4 +1,4 @@
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a459f1fdfe0bd365bf2def730e1529052c6487fd
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73b14da15ec731837ce2a45db658142bfbf5fe22
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The first line of this file holds the git revision number of the last
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merge done from the gofrontend repository.
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@ -194,7 +194,7 @@ func deferreturn(frame *bool) {
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// The gc compiler does this using assembler
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// code in jmpdefer.
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var fn func(unsafe.Pointer)
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*(**uintptr)(unsafe.Pointer(&fn)) = &pfn
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*(*uintptr)(unsafe.Pointer(&fn)) = uintptr(unsafe.Pointer(&pfn))
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fn(d.arg)
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}
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@ -259,7 +259,7 @@ func checkdefer(frame *bool) {
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gp._defer = d.link
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var fn func(unsafe.Pointer)
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*(**uintptr)(unsafe.Pointer(&fn)) = &pfn
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*(*uintptr)(unsafe.Pointer(&fn)) = uintptr(unsafe.Pointer(&pfn))
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fn(d.arg)
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freedefer(d)
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@ -345,7 +345,7 @@ func Goexit() {
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if pfn != 0 {
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var fn func(unsafe.Pointer)
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*(**uintptr)(unsafe.Pointer(&fn)) = &pfn
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*(*uintptr)(unsafe.Pointer(&fn)) = uintptr(unsafe.Pointer(&pfn))
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fn(d.arg)
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}
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@ -446,7 +446,7 @@ func gopanic(e interface{}) {
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if pfn != 0 {
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var fn func(unsafe.Pointer)
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*(**uintptr)(unsafe.Pointer(&fn)) = &pfn
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*(*uintptr)(unsafe.Pointer(&fn)) = uintptr(unsafe.Pointer(&pfn))
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fn(d.arg)
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if p.recovered {
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