tree 55ab705ca77332a378a820df25e08824a625dd1b
parent d5bc3b96c6fb758561e6274c8f69232623157ca4
author David Chase <drchase@google.com> 1527278893 -0400
committer David Chase <drchase@google.com> 1527698361 +0000

cmd/compile: do not allow regalloc to LoadReg G register

On architectures where G is stored in a register, it is
possible for a variable to allocated to it, and subsequently
that variable may be spilled and reloaded, for example
because of an intervening call.  If such an allocation
reaches a join point and it is the primary predecessor,
it becomes the target of a reload, which is only usually
right.

Fix: guard all the LoadReg ops, and spill value in the G
register (if any) before merges (in the same way that 387
FP registers are freed between blocks).

Includes test.

Fixes #25504.

Change-Id: I0482a53e20970c7315bf09c0e407ae5bba2fe05d
Reviewed-on: https://go-review.googlesource.com/114695
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>