…morestack

On LR machine, consider F calling G calling H, which grows stack.
The stack looks like
...
G's frame:
	... locals ...
	saved LR = return PC in F  <- SP points here at morestack
H's frame (to be created)

At morestack, we save
	gp.sched.pc = H's morestack call
	gp.sched.sp = H's entry SP (the arrow above)
	gp.sched.lr = return PC in G

Currently, when unwinding through morestack (if _TraceJumpStack
is set), we switch PC and SP but not LR. We then have
	frame.pc = H's morestack call
	frame.sp = H's entry SP (the arrow above)
As LR is not set, we load it from stack at *sp, so
	frame.lr = return PC in F
As the SP hasn't decremented at the morestack call,
	frame.fp = frame.sp = H's entry SP

Unwinding a frame, we have
	frame.pc = old frame.lr = return PC in F
	frame.sp = old frame.fp = H's entry SP a.k.a. G's SP
The PC and SP don't match. The unwinding will go off if F and G
have different frame sizes.

Fix this by preserving the LR when switching stack.

Also add code to detect infinite loop in unwinding.

TODO: add some test. I can reproduce the infinite loop (or throw
with added check) but the frequency is low.

Fixes #53111.
Updates #52116.

Change-Id: I6e1294f1c6e55f664c962767a1cf6c466a0c0eff
Reviewed-on: https://go-review.googlesource.com/c/go/+/400575
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Cherry Mui <[email protected]>
Reviewed-by: Eric Fang <[email protected]>
Reviewed-by: Benny Siegert <[email protected]>
(cherry picked from commit 74f0009)
Reviewed-on: https://go-review.googlesource.com/c/go/+/408822
Reviewed-by: Austin Clements <[email protected]>

…t timer is deleted

timerModifiedEarliest contains the lowest possible expiration for a
modified earlier timer, which may be earlier than timer0When because we
haven't yet updated the heap. Note "may", as the modified earlier timer
that set timerModifiedEarliest may have since been modified later or
deleted.

We can clear timerModifiedEarliest when the last timer is deleted
because by definition there must not be any modified earlier timers.

Why does this matter? checkTimersNoP claims that there is work to do if
timerModifiedEarliest has passed, causing findRunnable to loop back
around to checkTimers. But the code to clean up timerModifiedEarliest in
checkTimers (i.e., the call to adjusttimers) is conditional behind a
check that len(pp.timers) > 0.

Without clearing timerModifiedEarliest, a spinning M that would
otherwise go to sleep will busy loop in findRunnable until some other
work is available.

Note that changing the condition on the call to adjusttimers would also
be a valid fix. I took this approach because it feels a bit cleaner to
clean up timerModifiedEarliest as soon as it is known to be irrelevant.

For #51654.
Fixes #53846.

Change-Id: I3f3787c67781cac7ce87939c5706cef8db927dd5
Reviewed-on: https://go-review.googlesource.com/c/go/+/417434
Auto-Submit: Michael Pratt <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Michael Pratt <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
(cherry picked from commit c006b7a)
Reviewed-on: https://go-review.googlesource.com/c/go/+/417476

…ion is <= maxint

When the terminating condition is <= X, we need to make sure that
X+step doesn't overflow.

Fixes #53617

Change-Id: I36e5384d05b4d7168e48db6094200fcae409bfe5
Reviewed-on: https://go-review.googlesource.com/c/go/+/415219
Reviewed-by: Than McIntosh <[email protected]>
Run-TryBot: David Chase <[email protected]>
Reviewed-by: David Chase <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Keith Randall <[email protected]>
(cherry picked from commit 31b8c23)
Reviewed-on: https://go-review.googlesource.com/c/go/+/415415
Reviewed-by: Keith Randall <[email protected]>

…nment if LHS is address-taken

A composite literal assignment

x = T{field: v}

may be compiled to

x = T{}
x.field = v

We already do not use this form is RHS uses LHS. If LHS is
address-taken, RHS may uses LHS implicitly, e.g.

v = &x.field
x = T{field: *v}

The lowering above would change the value of RHS (*v).

Updates #52953.
Fixes #52960.

Change-Id: I3f798e00598aaa550b8c17182c7472fef440d483
Reviewed-on: https://go-review.googlesource.com/c/go/+/407014
Reviewed-by: Cuong Manh Le <[email protected]>
Run-TryBot: Cherry Mui <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
(cherry picked from commit 1c77137)
Reviewed-on: https://go-review.googlesource.com/c/go/+/419451
Reviewed-by: Matthew Dempsky <[email protected]>

In Float.GobDecode and Rat.GobDecode, check buffer sizes before
indexing slices.

Updates #53871
Fixes #54094

Change-Id: I1b652c32c2bc7a0e8aa7620f7be9b2740c568b0a
Reviewed-on: https://go-review.googlesource.com/c/go/+/417774
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Tatiana Bradley <[email protected]>
Run-TryBot: Roland Shoemaker <[email protected]>
(cherry picked from commit 055113e)
Reviewed-on: https://go-review.googlesource.com/c/go/+/419814
Reviewed-by: Julie Qiu <[email protected]>

Change-Id: Id21203787dc0bbca2548044d7bcc442204dfdd7d
Reviewed-on: https://go-review.googlesource.com/c/go/+/420554
Auto-Submit: Gopher Robot <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>
Run-TryBot: Gopher Robot <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>