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author | Matthew Dempsky <mdempsky@google.com> | 2020-04-20 11:14:36 -0700 |
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committer | Matthew Dempsky <mdempsky@google.com> | 2020-04-21 20:49:34 +0000 |
commit | 2a2423bd05da85dc7d0f8e7d12531623b69036a0 (patch) | |
tree | 0d92bc832877e14b3653f924cdc4f39c9ce11270 /test/escape2.go | |
parent | 181153369534c6987306c47630f9e4fbf07b467f (diff) | |
download | go-2a2423bd05da85dc7d0f8e7d12531623b69036a0.tar.gz go-2a2423bd05da85dc7d0f8e7d12531623b69036a0.zip |
cmd/compile: more precise analysis of method values
Previously for a method value "x.M", we always flowed x directly to
the heap, which led to the receiver argument generally needing to be
heap allocated.
This CL changes it to flow x to the closure and M's receiver
parameter. This allows receiver arguments to be stack allocated as
long as (1) the closure never escapes, *and* (2) method doesn't leak
its receiver parameter.
Within the standard library, this allows a handful of objects to be
stack allocated instead. Listed here are diagnostics that were
previously emitted by "go build -gcflags=-m std cmd" that are no
longer emitted:
archive/tar/writer.go:118:6: moved to heap: f
archive/tar/writer.go:208:6: moved to heap: f
archive/tar/writer.go:248:6: moved to heap: f
cmd/compile/internal/gc/initorder.go:252:2: moved to heap: d
cmd/compile/internal/gc/initorder.go:75:2: moved to heap: s
cmd/go/internal/generate/generate.go:206:7: &Generator literal escapes to heap
cmd/internal/obj/arm64/asm7.go:910:2: moved to heap: c
cmd/internal/obj/mips/asm0.go:415:2: moved to heap: c
cmd/internal/obj/pcln.go:294:22: new(pcinlineState) escapes to heap
cmd/internal/obj/s390x/asmz.go:459:2: moved to heap: c
crypto/tls/handshake_server.go:56:2: moved to heap: hs
Thanks to Cuong Manh Le for help coming up with this solution.
Fixes #27557.
Change-Id: I8c85d671d07fb9b53e11d2dd05949a34dbbd7e17
Reviewed-on: https://go-review.googlesource.com/c/go/+/228263
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Diffstat (limited to 'test/escape2.go')
-rw-r--r-- | test/escape2.go | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/test/escape2.go b/test/escape2.go index 4e30331380..cf24f4bebc 100644 --- a/test/escape2.go +++ b/test/escape2.go @@ -1386,8 +1386,7 @@ func (t *Tm) M() { // ERROR "t does not escape$" func foo141() { var f func() - // BAD: new(Tm) should not escape - t := new(Tm) // ERROR "new\(Tm\) escapes to heap$" + t := new(Tm) // ERROR "new\(Tm\) does not escape$" f = t.M // ERROR "t.M does not escape$" _ = f } |