[go] cmd/compile: don't drop same register twice

[Keith Randall (Gerrit)]

Keith Randall submitted the change

Change information

Commit message:

cmd/compile: don't drop same register twice

For instructions that clobber both of their input registers, make
sure we don't clobber the same register twice when both input
registers are the same.

This is rare, but it can happen.

Fixes #77604

Change-Id: I794249cf43a8cc4ab3262055daef9193e2442f73

Reviewed-on: https://go-review.googlesource.com/c/go/+/745621

Reviewed-by: Keith Randall <k...@google.com>

LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Reviewed-by: Jorropo <jorro...@gmail.com>

Reviewed-by: Dmitri Shuralyov <dmit...@google.com>

Files:

• M src/cmd/compile/internal/ssa/regalloc.go
• A test/fixedbugs/issue77604.go

Change size: S

Delta: 2 files changed, 21 insertions(+), 1 deletion(-)

Branch: refs/heads/master

Submit Requirements:

• Code-Review: +1 by Keith Randall, +2 by Jorropo, +1 by Dmitri Shuralyov
• TryBots-Pass: LUCI-TryBot-Result+1 by Go LUCI

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Gerrit

Gerrit-MessageType: merged

Gerrit-Project: go

Gerrit-Branch: master

Gerrit-Change-Id: I794249cf43a8cc4ab3262055daef9193e2442f73

Gerrit-Change-Number: 745621

Gerrit-PatchSet: 2

Gerrit-Owner: Keith Randall <k...@golang.org>

Gerrit-Reviewer: Dmitri Shuralyov <dmit...@google.com>

Gerrit-Reviewer: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Gerrit-Reviewer: Jorropo <jorro...@gmail.com>

Gerrit-Reviewer: Keith Randall <k...@golang.org>

Gerrit-Reviewer: Keith Randall <k...@google.com>

Gerrit-CC: Dmitri Shuralyov <dmit...@golang.org>