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runtime, cmd/internal/obj: get rid of rewindmorestack

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In the function prologue, we emit a jump to the beginning of
the function immediately after calling morestack. And in the
runtime stack growing code, it decodes and emulates that jump.
This emulation was necessary before we had per-PC SP deltas,
since the traceback code assumed that the frame size was fixed
for the whole function, except on the first instruction where
it was 0. Since we now have per-PC SP deltas and PCDATA, we
can correctly record that the frame size is 0. This makes the
emulation unnecessary.

This may be helpful for registerized calling convention, where
there may be unspills of arguments after calling morestack. It
also simplifies the runtime.

Change-Id: I7ebee31eaee81795445b33f521ab6a79624c4ceb
Reviewed-on: https://go-review.googlesource.com/30138
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Cherry Zhang 2016-10-02 17:10:13 -04:00
parent 56b746974c
commit 4c9a372946
13 changed files with 103 additions and 147 deletions
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3
src/runtime/stack.go
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@ -602,7 +602,7 @@ func adjustpointers(scanp unsafe.Pointer, cbv *bitvector, adjinfo *adjustinfo, f
}
if minp <= p && p < maxp {
if stackDebug >= 3 {
print("adjust ptr ", p, " ", funcname(f), "\n")
print("adjust ptr ", hex(p), " ", funcname(f), "\n")
}
if useCAS {
ppu := (*unsafe.Pointer)(unsafe.Pointer(pp))
@ -957,7 +957,6 @@ func newstack() {
thisg.m.morebuf.lr = 0
thisg.m.morebuf.sp = 0
thisg.m.morebuf.g = 0
rewindmorestack(&gp.sched)
// NOTE: stackguard0 may change underfoot, if another thread
// is about to try to preempt gp. Read it just once and use that same