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Matthew Dempsky d6294e00f0 cmd/compile: fix devirtualization bug with unified IR
As a consistency check in devirtualization, when we determine `i` (of
interface type `I`) always has dynamic type `T`, we insert a type
assertion `i.(T)`. This emits an itab check for `go:itab.T,I`, but
it's always true (and so SSA optimizes it away).

However, if `I` is instead the generic interface type `I[T]`, then
`go:itab.T,I[int]` and `go:itab.T,I[go.shape.int]` are equivalent but
distinct itabs. And notably, we'll have originally created the
interface value using the former; but the (non-dynamic) TypeAssertExpr
created by devirtualization would ultimately emit a comparison against
the latter. This comparison would then evaluate false, leading to a
spurious type assertion panic at runtime.

The comparison is just meant as an extra safety check, so it should be
safe to just disable. But for now, it's simpler/safer to just punt on
devirtualization in this case. (The non-unified frontend doesn't
devirtualize this either.)

Change-Id: I6a8809bcfebc9571f32e289fa4bc6a8b0d21ca46
Reviewed-on: https://go-review.googlesource.com/c/go/+/424774
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
2022-08-18 17:26:32 +00:00
.github .github: remove duplicate security link 2022-01-07 17:55:09 +00:00
api crypto/subtle: add XORBytes 2022-08-17 18:47:33 +00:00
doc doc: move Go 1.19 release notes to x/website 2022-08-01 18:07:12 +00:00
lib/time lib/time, time/tzdata: update to 2022b 2022-08-11 20:03:19 +00:00
misc misc/cgo/testsanitizers: fix code to detect gcc version correctly 2022-08-11 17:23:33 +00:00
src cmd/compile: fix devirtualization bug with unified IR 2022-08-18 17:26:32 +00:00
test cmd/compile: fix devirtualization bug with unified IR 2022-08-18 17:26:32 +00:00
.gitattributes all: treat all files as binary, but check in .bat with CRLF 2020-06-08 15:31:43 +00:00
.gitignore internal/buildcfg: move build configuration out of cmd/internal/objabi 2021-04-16 19:20:53 +00:00
codereview.cfg codereview.cfg: add codereview.cfg for master branch 2021-02-19 18:44:53 +00:00
CONTRIBUTING.md all: restore changes from faulty merge/revert 2018-02-12 20:13:59 +00:00
LICENSE
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README.md README.md: update wiki link 2022-04-26 16:21:18 +00:00
SECURITY.md SECURITY.md: replace golang.org with go.dev 2022-04-26 19:59:47 +00:00

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