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[dev.ssa] cmd/compile/internal/gc, runtime: use 32-bit load for writeBarrier check

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Use 32-bit load for writeBarrier check on all architectures.
Padding added to runtime structure.

Updates #15365, #15492.

Change-Id: I5d3dadf8609923fe0fe4fcb384a418b7b9624998
Reviewed-on: https://go-review.googlesource.com/22855
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Cherry Zhang 2016-05-06 10:12:57 -07:00
parent e1a2ea88d0
commit fdc4a964d2
2 changed files with 9 additions and 10 deletions
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10
src/cmd/compile/internal/gc/ssa.go
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@ -3029,10 +3029,9 @@ func (s *state) insertWBmove(t *Type, left, right *ssa.Value, line int32) {
aux := &ssa.ExternSymbol{Typ: Types[TBOOL], Sym: syslook("writeBarrier").Sym}
flagaddr := s.newValue1A(ssa.OpAddr, Ptrto(Types[TUINT32]), aux, s.sb)
// TODO: select the .enabled field. It is currently first, so not needed for now.
// Load word, test byte, avoiding partial register write from load byte.
// Load word, test word, avoiding partial register write from load byte.
flag := s.newValue2(ssa.OpLoad, Types[TUINT32], flagaddr, s.mem())
flag = s.newValue1(ssa.OpTrunc64to8, Types[TBOOL], flag)
flag = s.newValue2(ssa.OpNeq32, Types[TBOOL], flag, s.constInt32(Types[TUINT32], 0))
b := s.endBlock()
b.Kind = ssa.BlockIf
b.Likely = ssa.BranchUnlikely
@ -3080,10 +3079,9 @@ func (s *state) insertWBstore(t *Type, left, right *ssa.Value, line int32, skip
aux := &ssa.ExternSymbol{Typ: Types[TBOOL], Sym: syslook("writeBarrier").Sym}
flagaddr := s.newValue1A(ssa.OpAddr, Ptrto(Types[TUINT32]), aux, s.sb)
// TODO: select the .enabled field. It is currently first, so not needed for now.
// Load word, test byte, avoiding partial register write from load byte.
// Load word, test word, avoiding partial register write from load byte.
flag := s.newValue2(ssa.OpLoad, Types[TUINT32], flagaddr, s.mem())
flag = s.newValue1(ssa.OpTrunc64to8, Types[TBOOL], flag)
flag = s.newValue2(ssa.OpNeq32, Types[TBOOL], flag, s.constInt32(Types[TUINT32], 0))
b := s.endBlock()
b.Kind = ssa.BlockIf
b.Likely = ssa.BranchUnlikely

9
src/runtime/mgc.go
View File

@ -220,10 +220,11 @@ var gcphase uint32
// The compiler knows about this variable.
// If you change it, you must change the compiler too.
var writeBarrier struct {
enabled bool // compiler emits a check of this before calling write barrier
needed bool // whether we need a write barrier for current GC phase
cgo bool // whether we need a write barrier for a cgo check
alignme uint64 // guarantee alignment so that compiler can use a 32 or 64-bit load
enabled bool // compiler emits a check of this before calling write barrier
pad [3]byte // compiler uses 32-bit load for "enabled" field
needed bool // whether we need a write barrier for current GC phase
cgo bool // whether we need a write barrier for a cgo check
alignme uint64 // guarantee alignment so that compiler can use a 32 or 64-bit load
}
// gcBlackenEnabled is 1 if mutator assists and background mark