go, branch go1.8.3

[release-branch.go1.8] go1.8.3

2017-05-24T18:14:11Z

Change-Id: I048f21f8ca68758fdd7ac875f7db5e4ed1930f3b Reviewed-on: https://go-review.googlesource.com/44037 Reviewed-by: Brad Fitzpatrick

[release-branch.go1.8] doc: document go1.8.3

2017-05-24T18:12:51Z

Change-Id: I5d55c3b1011dd10552d8e740fb65886306d91b5c Reviewed-on: https://go-review.googlesource.com/44035 Reviewed-by: Brad Fitzpatrick Reviewed-on: https://go-review.googlesource.com/44036

[release-branch.go1.8] cmd/compile: don't move spills to loop exits where the spill is dead

2017-05-24T15:44:39Z

We shouldn't move a spill to a loop exit where the spill itself is dead. The stack location assigned to the spill might already be reused by another spill at this point. The case we previously handled incorrectly is the one where the value being spilled is still live, but the spill itself is dead. Fixes #20472 Patching directly on the release branch because the spill moving code has already been rewritten for 1.9. (And it doesn't have this bug.) Change-Id: I26c5273dafd98d66ec448750073c2b354ef89ad6 Reviewed-on: https://go-review.googlesource.com/44033 Run-TryBot: Keith Randall TryBot-Result: Gobot Gobot Reviewed-by: Cherry Zhang

[release-branch.go1.8] cmd/compile: zero ambiguously live variables at VARKILLs

2017-05-24T15:23:47Z

This is a redo of CL 41076 backported to the 1.8 release branch. There were major conflicts, so I had to basically rewrite it again from scratch. The way Progs are allocated changed. Liveness analysis and Prog generation got reordered. Liveness analysis changed from running on gc.BasicBlock to ssa.Block. All that makes the logic quite a bit different. Please review carefully. From CL 41076: At VARKILLs, zero a variable if it is ambiguously live. After the VARKILL anything this variable references might be collected. If it were to become live again later, the GC will see references to already-collected objects. We don't know a variable is ambiguously live until very late in compilation (after lowering, register allocation, ...), so it is hard to generate the code in an arch-independent way. We also have to be careful not to clobber any registers. Fortunately, this almost never happens so performance is ~irrelevant. There are only 2 instances where this triggers in the stdlib. Fixes #20029 Change-Id: Ibb757eec58ee07f40df5e561b19d315684dc4bda Reviewed-on: https://go-review.googlesource.com/43998 Run-TryBot: Keith Randall TryBot-Result: Gobot Gobot Reviewed-by: Matthew Dempsky

[release-branch.go1.8] runtime: use pselect6 for usleep on linux/386

2017-05-23T23:21:19Z

Commit 4dcba023c6 replaced select with pselect6 on linux/amd64 and linux/arm, but it turns out the Android emulator uses linux/386. This makes the equivalent change there, too. Fixes #20409 more. Change-Id: If542d6ade06309aab8758d5f5f6edec201ca7670 Reviewed-on: https://go-review.googlesource.com/44011 Run-TryBot: Austin Clements TryBot-Result: Gobot Gobot Reviewed-by: Brad Fitzpatrick Reviewed-by: Ian Lance Taylor (cherry picked from commit ecad34a40ea390ddf5ba2da8f3c3f2c5f15297c8) Reviewed-on: https://go-review.googlesource.com/44002 Run-TryBot: Brad Fitzpatrick Reviewed-by: Chris Broadfoot

[release-branch.go1.8] runtime: use pselect6 for usleep on linux/amd64 and linux/arm

2017-05-23T23:21:13Z

Android O black-lists the select system call because its libc, Bionic, does not use this system call. Replace our use of select with pselect6 (which is allowed) on the platforms that support targeting Android. linux/arm64 already uses pselect6 because there is no select on arm64, so only linux/amd64 and linux/arm need changing. pselect6 has been available since Linux 2.6.16, which is before Go's minimum requirement. Fixes #20409. Change-Id: Ic526b5b259a9e01d2f145a1f4d2e76e8c49ce809 Reviewed-on: https://go-review.googlesource.com/43641 Run-TryBot: Austin Clements TryBot-Result: Gobot Gobot Reviewed-by: Brad Fitzpatrick Reviewed-by: Ian Lance Taylor (cherry picked from commit 4dcba023c62d7f7968abc54fa5d38d2bf11412ba) Reviewed-on: https://go-review.googlesource.com/44001 Run-TryBot: Brad Fitzpatrick Reviewed-by: Chris Broadfoot

[release-branch.go1.8] cmd/compile: ignore types when considering tuple select for CSE

2017-05-23T21:25:37Z

Fixes #20097 Change-Id: I3c9626ccc8cd0c46a7081ea8650b2ff07a5d4fcd Reviewed-on: https://go-review.googlesource.com/41505 Run-TryBot: Todd Neal TryBot-Result: Gobot Gobot Reviewed-by: Keith Randall Reviewed-on: https://go-review.googlesource.com/43997 Run-TryBot: Chris Broadfoot Reviewed-by: Brad Fitzpatrick

[release-branch.go1.8] net/http: update bundled http2 for gracefulShutdownCh lock contention slowdown

2017-05-23T20:37:03Z

This updates the bundled x/net/http2 repo to git rev 186fd3fc (from the net repo's release-branch.go1.8) for: [release-branch.go1.8] http2: fix lock contention slowdown due to gracefulShutdownCh https://golang.org/cl/43459 Fixes #20302 Change-Id: Ia01a44c6749292de9c16ca330bdebe1e52458b18 Reviewed-on: https://go-review.googlesource.com/43996 Run-TryBot: Brad Fitzpatrick Reviewed-by: Chris Broadfoot TryBot-Result: Gobot Gobot

[release-branch.go1.8] cmd/compile: fix s390x unsigned comparison constant merging rules

2017-05-23T20:03:07Z

On s390x unsigned integer comparisons with immediates require the immediate to be an unsigned 32-bit integer. The rule was checking that the immediate was a signed 32-bit integer. This CL also adds a test for comparisons that could be turned into compare with immediate or equivalent instructions (depending on architecture and optimizations applied). Cherry-pick of CL 40433 and CL 40873. Fixes #19940. Reviewed-on: https://go-review.googlesource.com/40931 Reviewed-by: Brad Fitzpatrick Run-TryBot: Brad Fitzpatrick TryBot-Result: Gobot Gobot Change-Id: I3daaeaa40d7637bd4421e6b8d37ea4ffd74448ce Reviewed-on: https://go-review.googlesource.com/43994 Reviewed-by: Brad Fitzpatrick

[release-branch.go1.8] cmd/go: if we get a C compiler dwarf2 warning, try without -g

2017-05-23T20:03:04Z

Backport of CL 38072 Fixes #14705 Reviewed-on: https://go-review.googlesource.com/42500 Run-TryBot: Brad Fitzpatrick Reviewed-by: Ian Lance Taylor Change-Id: Ia6ce2a41434aef2f8745a6a862ea66608b1e25f7 Reviewed-on: https://go-review.googlesource.com/43995 Reviewed-by: Brad Fitzpatrick