tree cf72fa9d67043c73136a39a3815045397a5aedc4
parent 5890e25b7ccb2d2249b2f8a02ef5dbc36047868b
author Michael Munday <mike.munday@ibm.com> 1531813170 +0100
committer Michael Munday <mike.munday@ibm.com> 1531839534 +0000

cmd/compile: keep autos if their address reaches a control value

Autos must be kept if their address reaches the control value of a
block. We didn't see this before because it is rare for an auto's
address to reach a control value without also reaching a phi or
being written to memory. We can probably optimize away the
comparisons that lead to this scenario since autos cannot alias
with pointers from elsewhere, however for now we take the
conservative approach and just ensure the auto is properly
initialised if its address reaches a control value.

Fixes #26407.

Change-Id: I02265793f010a9e001c3e1a5397c290c6769d4de
Reviewed-on: https://go-review.googlesource.com/124335
Reviewed-by: David Chase <drchase@google.com>