| commit | 78952c06c53c8455d03430b17b5a7fe2693b5d35 | [log] [tgz] |
|---|---|---|
| author | Keith Randall <khr@golang.org> | Thu Sep 21 12:52:38 2017 -0700 |
| committer | Russ Cox <rsc@golang.org> | Wed Oct 25 20:24:00 2017 +0000 |
| tree | d90f34c4cd3acd94a03a18513422d703787c8d92 | |
| parent | 79996e4a1d33b7404ee076d7455ff8dcc7270250 [diff] |
[release-branch.go1.9] cmd/compile: fix sign-extension merging rules If we have y = <int16> (MOVBQSX x) z = <int32> (MOVWQSX y) We used to use this rewrite rule: (MOVWQSX x:(MOVBQSX _)) -> x But that resulted in replacing z with a value whose type is only int16. Then if z is spilled and restored, it gets zero extended instead of sign extended. Instead use the rule (MOVWQSX (MOVBQSX x)) -> (MOVBQSX x) The result is has the correct type, so it can be spilled and restored correctly. It might mean that a few more extension ops might not be eliminated, but that's the price for correctness. Fixes #21963 Change-Id: I6ec82c3d2dbe43cc1fee6fb2bd6b3a72fca3af00 Reviewed-on: https://go-review.googlesource.com/65290 Reviewed-by: Cherry Zhang <cherryyz@google.com> Run-TryBot: Cherry Zhang <cherryyz@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-on: https://go-review.googlesource.com/70986 Run-TryBot: Russ Cox <rsc@golang.org> Reviewed-by: Keith Randall <khr@golang.org>
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