update LLVM with fix for PR32379 #40779

arielb1 · 2017-03-23T23:27:40Z

The "root" codegen bug fixed here is that, when generating ARM code, unpatched LLVM 3.9/3.9.1 miscompiles bit operations in rare circumstances - this can cause user code compiled via LLVM (through both rustc and clang) to subtly return incorrect results - for more details, see the test in this PR or in the LLVM rare report.

One effect of that LLVM bug is that rustc 1.17 (and possibly other versions) is miscompiled on ARM. The code generated by a miscompiled rustc lacks destructor calls in many circumstances.

Users who run an affected/miscompiled rustc - 1.17 or above - on an ARM build machine will be affected by the (fairly blatant) missing destructor bug, regardless of the target architecture (this includes the official 1.17.0-beta.1, 1.17.0-beta.2, and some official 1.17/1.18 nightlies).

Users who use an affected LLVM (that's any unpatched LLVM 3.9/3.9.1), whether through rustc (in any version that supports 3.9 - that's 1.12 or above) or through clang, who compile code to an ARM target architecture might be affected by the (fairly hard to hit) bit operation bug, regardless of the build machine.

Distributors and user who want to compile rustc using their own LLVM should apply the patch to avoid miscompilations.

r? @alexcrichton
Beta-nominating because regression (rustc 1.16 is not blatantly miscompiled). This also picks a fix for the (MSVC-affecting) PR29151.

Fixes rust-lang#40593.

alexcrichton · 2017-03-23T23:30:13Z

@bors: r+

Awesome work finding this bug! Seems like a great backport.

FWIW we have tons of bug fixes on our LLVM fork that correspond to no actual release of LLVM. Unless you're using literally our LLVM then there's basically guaranteed to be at least one regression waiting for you if you use the compiler long enough.

bors · 2017-03-23T23:30:14Z

📌 Commit bd52ff1 has been approved by alexcrichton

arielb1 · 2017-03-23T23:37:50Z

@alexcrichton

That's mostly MSVC fixes + optimizations, but I recommend all the distributors who want a working rustc to at least include a fix for https://bugs.llvm.org/show_bug.cgi?id=29163 (but that is included in 3.9.1).

sanxiyn · 2017-03-24T03:31:53Z

FYI, the importance of fix for LLVM 29163 is that without it rustup will segfault: see #36023.

arielb1 · 2017-03-24T11:31:03Z

travis failure is a network error on Mac - the standard builder is green.

pmarcelll · 2017-03-24T16:21:45Z

I just realized that the latest nightly is still 1.17, not 1.18.
cc @brson (Sorry for the noise.)

arielb1 · 2017-03-24T20:30:05Z

@bors p=1

Try to get all 1.18 nightlies clean.

bors · 2017-03-24T21:09:38Z

⌛ Testing commit bd52ff1 with merge 3da4023...

@alexcrichton

update LLVM with fix for PR32379 Fixes #40593. The "root" codegen bug fixed here is that, when generating ARM code, unpatched LLVM 3.9/3.9.1 miscompiles bit operations in rare circumstances - this can cause user code compiled via LLVM (through both `rustc` and `clang`) to subtly return incorrect results - for more details, see the test in this PR or in the LLVM rare report. One effect of that LLVM bug is that `rustc` 1.17 (and possibly other versions) is miscompiled on ARM. The code generated by a miscompiled `rustc` lacks destructor calls in many circumstances. Users who run an affected/miscompiled `rustc` - 1.17 or above - on an ARM build machine will be affected by the (fairly blatant) missing destructor bug, regardless of the target architecture (this includes the official `1.17.0-beta.1`, `1.17.0-beta.2`, and some official 1.17/1.18 nightlies). Users who use an affected LLVM (that's any unpatched LLVM 3.9/3.9.1), whether through `rustc` (in any version that supports 3.9 - that's 1.12 or above) or through `clang`, who compile code to an ARM target architecture might be affected by the (fairly hard to hit) bit operation bug, regardless of the build machine. Distributors and user who want to compile rustc using their own LLVM should apply the [patch](llvm-mirror/llvm@cdc303e) to avoid miscompilations. r? @alexcrichton Beta-nominating because regression (rustc 1.16 is not blatantly miscompiled). This also picks a fix for the (MSVC-affecting) PR29151.

bors · 2017-03-24T23:46:39Z

☀️ Test successful - status-appveyor, status-travis
Approved by: alexcrichton
Pushing 3da4023 to master...

Backport PRs to beta Backport of * #40967 * #40836 * #40779 * #40888 Also includes a cargo submodule update

@arielb1

There was a serious ARM codegen bug in LLVM that was fixed by rust-lang#40779, also backported to beta. This updates stage0 to 1.17.0-beta.3 to pick up that change, so ARM can bootstrap natively again. Fixes rust-lang#41291 cc @arielb1

@arielb1