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runtime: skip stack barrier copy when there are no pointers

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After CL 31455, "go fun(n)" may put "n" to write barrier buffer
when there are no pointers in fun's arguments.

Fixes #29362

Change-Id: Icfa42b8759ce8ad9267dcb3859c626feb6fda381
Reviewed-on: https://go-review.googlesource.com/c/155779
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Inada Naoki 2018-12-27 00:47:20 +09:00 committed by Keith Randall
parent 30c0a0d33f
commit 5372257e60
1 changed files with 5 additions and 3 deletions
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2
src/runtime/proc.go
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@ -3303,11 +3303,13 @@ func newproc1(fn *funcval, argp *uint8, narg int32, callergp *g, callerpc uintpt
if writeBarrier.needed && !_g_.m.curg.gcscandone {
f := findfunc(fn.fn)
stkmap := (*stackmap)(funcdata(f, _FUNCDATA_ArgsPointerMaps))
if stkmap.nbit > 0 {
// We're in the prologue, so it's always stack map index 0.
bv := stackmapdata(stkmap, 0)
bulkBarrierBitmap(spArg, spArg, uintptr(narg), 0, bv.bytedata)
}
}
}
memclrNoHeapPointers(unsafe.Pointer(&newg.sched), unsafe.Sizeof(newg.sched))
newg.sched.sp = sp