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| author | Keith Randall <khr@golang.org> | 2017-04-19 11:19:53 -0700 |
|---|---|---|
| committer | Keith Randall <khr@golang.org> | 2017-04-20 23:47:43 +0000 |
| commit | 38dee12dea062337a9591b49a9525d85afedc09c (patch) | |
| tree | f841123575aa8604a67b8a5baa0b1902600ef3f6 /src/cmd/compile/internal/mips | |
| parent | 7bd1c210858f308ee9a73b6a3b953c477ebb294e (diff) | |
| download | go-38dee12dea062337a9591b49a9525d85afedc09c.tar.gz go-38dee12dea062337a9591b49a9525d85afedc09c.zip | |
cmd/compile: zero ambiguously live variables at VARKILLs
At VARKILLs, zero a variable if it is ambiguously live.
After the VARKILL anything this variable references
might be collected. If it were to become live again later,
the GC will see references to already-collected objects.
We don't know a variable is ambiguously live until very
late in compilation (after lowering, register allocation, ...),
so it is hard to generate the code in an arch-independent way.
We also have to be careful not to clobber any registers.
Fortunately, this almost never happens so performance is ~irrelevant.
There are only 2 instances where this triggers in the stdlib.
Fixes #20029
Change-Id: Ia9585a91d7b823fad4a9d141d954464cc7af31f4
Reviewed-on: https://go-review.googlesource.com/41076
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Diffstat (limited to 'src/cmd/compile/internal/mips')
| -rw-r--r-- | src/cmd/compile/internal/mips/galign.go | 1 | ||||
| -rw-r--r-- | src/cmd/compile/internal/mips/ggen.go | 16 |
2 files changed, 17 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/mips/galign.go b/src/cmd/compile/internal/mips/galign.go index f0ef6cd100..77ec78aabf 100644 --- a/src/cmd/compile/internal/mips/galign.go +++ b/src/cmd/compile/internal/mips/galign.go @@ -19,6 +19,7 @@ func Init(arch *gc.Arch) { arch.REGSP = mips.REGSP arch.MAXWIDTH = (1 << 31) - 1 arch.ZeroRange = zerorange + arch.ZeroAuto = zeroAuto arch.Ginsnop = ginsnop arch.SSAMarkMoves = func(s *gc.SSAGenState, b *ssa.Block) {} arch.SSAGenValue = ssaGenValue diff --git a/src/cmd/compile/internal/mips/ggen.go b/src/cmd/compile/internal/mips/ggen.go index dafa341a13..5a9f590763 100644 --- a/src/cmd/compile/internal/mips/ggen.go +++ b/src/cmd/compile/internal/mips/ggen.go @@ -43,6 +43,22 @@ func zerorange(pp *gc.Progs, p *obj.Prog, off, cnt int64, _ *uint32) *obj.Prog { return p } +func zeroAuto(pp *gc.Progs, n *gc.Node) { + // Note: this code must not clobber any registers. + sym := gc.Linksym(n.Sym) + size := n.Type.Size() + for i := int64(0); i < size; i += 4 { + p := pp.Prog(mips.AMOVW) + p.From.Type = obj.TYPE_REG + p.From.Reg = mips.REGZERO + p.To.Type = obj.TYPE_MEM + p.To.Name = obj.NAME_AUTO + p.To.Reg = mips.REGSP + p.To.Offset = n.Xoffset + i + p.To.Sym = sym + } +} + func ginsnop(pp *gc.Progs) { p := pp.Prog(mips.ANOR) p.From.Type = obj.TYPE_REG |