Upgrade LLVM

[alexcrichton]

This is a bit of an interesting upgrade to LLVM. Upstream LLVM has started using C++11 features, so they require a C++11 compiler to build. I've updated all the bots to have a C++11 compiler, and they appear to be building LLVM successfully:

• Linux bots - I added gcc/g++ 4.7 (good enough)
• Android bots - same as the linux ones
• Mac bots - I installed the most recent command line tools for Lion which gives us clang 3.2, but LLVM wouldn't build unless it was explicitly asked to link to libc++ instead of libstdc++. This involved tweaking mklldeps.py and the configure script to get things to work out
• Windows bots - mingw-w64 has gcc 4.8.1 which is sufficient for building LLVM (hurray!)
• BSD bots - I updated FreeBSD to 10.0 which brought with it a relevant version of clang.

The largest fallout I've seen so far is that the test suite doesn't work at all on FreeBSD 10. We've already stopped gating on FreeBSD due to #13427 (we used to be on freebsd 9), so I don't think this puts us in too bad of a situation. I will continue to attempt to fix FreeBSD and the breakage on there.

The LLVM update brings with it all of the recently upstreamed LLVM patches. We only have one local patch now which is just an optimization, and isn't required to use upstream LLVM. I want to maintain compatibility with LLVM 3.3 and 3.4 while we can, and this upgrade is keeping us up to date with the 3.5 release. Once 3.5 is release we will in theory no longer require a bundled LLVM.

[alexcrichton]

I realized that I can test locally against LLVM snapshots to ensure that we still work with 3.3/3.4, so I'm going to hold off r=thestinger'ing the last commit until I can verify that it does indeed fix 3.3/3.4

[alexcrichton]

removing r+, @brson has worries about the linux-snap builder which I forgot to update. It's going to be a little tricky.

[alexcrichton]

ping @michaelwoerister

These seem to be failing because rbreak zzz isn't working in GDB. I have 7.6.1 installed locally (which works), but the bots have gdb 7.4 installed locally (which apparently doesn't work). For example:

My gdb:

$ ./x86_64-unknown-linux-gnu/stage2/bin/rustc -g ./src/test/debug-info/simple-struct.rs 
$ gdb ./simple-struct              
GNU gdb (GDB) 7.6.1-ubuntu
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/alex/code/rust4/simple-struct...done.
(gdb) rbreak zzz
Breakpoint 1 at 0x404460: file src/test/debug-info/simple-struct.rs, line 182.
static void simple-struct::zzz();
(gdb) 

gdb on the bots

$ ./x86_64-unknown-linux-gnu/stage2/bin/rustc ../src/test/debug-info/simple-struct.rs -g
$ gdb ./simple-struct 
GNU gdb (Ubuntu/Linaro 7.4-2012.04-0ubuntu2) 7.4-2012.04
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.launchpad.net/gdb-linaro/>...
Reading symbols from /home/ubuntu/src/rust-buildbot/slave/try-linux/build/obj/simple-struct...done.
(gdb) rbreak zzz
(gdb) 

There was a change to debug info during this upgrade, the LLVMDIBuilderCreateLexicalBlock function now takes a Discriminator argument at the end. I saw in LLVM they set this to 0 in a few places, so I set this to 0 always. There may have been other debuginfo changes throughout this upgrade which messed with this.

Basically, does this look like a familiar issue or something similar?

[alexcrichton]

Hm, it appears that a discriminator doesn't have much to do with what appears to be the problem.

It just appears that debug info isn't working at all with gdb 7.4 after this upgrade...

[michaelwoerister]

I haven't seen anything like this before. I will take a look at it next
Wednesday.

On 18.04.2014 09:40, Alex Crichton wrote:

Hm, it appears that a discriminator doesn't have much to do with what
appears to be the problem.

It just appears that debug info isn't working at all with gdb 7.4
after this upgrade...

Reply to this email directly or view it on GitHub [1].

Links:

[1] #13513 (comment)

[alexcrichton]

Hm, interesting development:

fn main() {
    zzz();
}
fn zzz() {()}

fn main() {
    zzz();
}
fn zzz() {}

In gdb 7.4, rbreak zzz woks on the second example, but not the first. Sadly changing all the debug-info tests only fixes 3 tests... (79 still failing)

[alexcrichton]

False alarms all around! Looks like LLVM is just emitting newer dwarf. Compiling with -C llvm-args=-dwarf-version=3 fixes all tests.