Fails to build against llvm 3.6 rc1

[sylvestre]

With the following error:

g++  -O2  -Wall -Werror -g -fPIC -m64 -fno-rtti -MMD -MP -MT  x86_64-unknown-linux-gnu/rustllvm/ExecutionEngineWrapper.o -MF x86_64-unknown-linux-gnu/rustllvm/ExecutionEngineWrapper.d -c -o  x86_64-unknown-linux-gnu/rustllvm/ExecutionEngineWrapper.o    -iquote /usr/lib/llvm-3.6/include  -DNDEBUG -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -g -O2 -fomit-frame-pointer -std=c++11 -fvisibility-inlines-hidden -fno-exceptions -fPIC -ffunction-sections -fdata-sections -Wcast-qual  -iquote /usr/lib/llvm-3.6/include -iquote /home/sylvestre/dev/debian/rust/src/rustllvm/include /home/sylvestre/dev/debian/rust/src/rustllvm/ExecutionEngineWrapper.cpp
/home/sylvestre/dev/debian/rust/src/rustllvm/ExecutionEngineWrapper.cpp: In function ‘LLVMOpaqueExecutionEngine* LLVMBuildExecutionEngine(LLVMModuleRef, LLVMRustJITMemoryManagerRef)’:
/home/sylvestre/dev/debian/rust/src/rustllvm/ExecutionEngineWrapper.cpp:97:34: error: no matching function for call to ‘llvm::EngineBuilder::setMCJITMemoryManager(RustJITMemoryManager*&)’
         .setMCJITMemoryManager(mm)
                                  ^
/home/sylvestre/dev/debian/rust/src/rustllvm/ExecutionEngineWrapper.cpp:97:34: note: candidate is:
In file included from /home/sylvestre/dev/debian/rust/src/rustllvm/rustllvm.h:34:0,
                 from /home/sylvestre/dev/debian/rust/src/rustllvm/ExecutionEngineWrapper.cpp:11:
/usr/lib/llvm-3.6/include/llvm/ExecutionEngine/ExecutionEngine.h:528:18: note: llvm::EngineBuilder& llvm::EngineBuilder::setMCJITMemoryManager(std::unique_ptr<llvm::RTDyldMemoryManager>)
   EngineBuilder &setMCJITMemoryManager(std::unique_ptr<RTDyldMemoryManager> mcjmm);
                  ^
/usr/lib/llvm-3.6/include/llvm/ExecutionEngine/ExecutionEngine.h:528:18: note:   no known conversion for argument 1 from ‘RustJITMemoryManager*’ to ‘std::unique_ptr<llvm::RTDyldMemoryManager>’
/home/sylvestre/dev/debian/rust/mk/rustllvm.mk:47: recipe for target 'x86_64-unknown-linux-gnu/rustllvm/ExecutionEngineWrapper.o' failed
make[2]: *** [x86_64-unknown-linux-gnu/rustllvm/ExecutionEngineWrapper.o] Error 1

[lucab]

The embedded fork is stuck somewhere between 3.5 and 3.6. I managed to rebase it without too many issues at https://github.com/lucab/llvm/tree/lucab/rust-llvm-3.6.0rc1.

On the other hand, rustllvm needs some facelifting, as there have been at least the following breaking changes in the middle:

• split between Metadata and Value, rev223802
• new intrinsic syntax for llvm.dbg.declare/llvm.dbg.value as described here, rev218787

[lucab]

On the bright side, our current delta to 3.6.0rc1 is:

• a NullCheckElimination pass. I spoke with @zwarich who told me this is too specific to rust (and the upstream status of a range analysis pass not too clear), so will stay there for now
• a small optimization to getPassInfo(). The story of this is a bit unfortunate, and got no reaction when sent to upstream ML.

[michaelwoerister]

FYI: I've been looking into the metadata/value split issue since that mostly affects debuginfo. Also, the llvm.dbg.declare/llvm.dbg.value changes require a bit more work if we also still want to be able to compile against LLVM < 3.6. I'm currently working on getting that fixed.

[richo]

I started poking at this, and then successfully nerdsniped Alex into having another look. Our (mostly his) work so far is here if you want a starting point: https://github.com/alexcrichton/rust/tree/update-llvm

[michaelwoerister]

Let's pull @alexcrichton into the discussion.

[michaelwoerister]

This looks very similar to what I've done, naturally. But just following the metadata split will make it impossible to support both 3.5 and 3.6. I plan to solve this problem by providing a more abstract API for declaring local variables in debuginfo and implement a bit more logic RustWrapper.cpp, where we can better special-case on LLVM version.

[michaelwoerister]

For reference, here is the branch I'm working on:
https://github.com/michaelwoerister/rust/tree/llvm-36-preparations

It only concerns itself with the metadata/debuginfo changes.

[michaelwoerister]

I plan to solve this problem by providing a more abstract API for declaring local variables in debuginfo

A different approach would be to add a version suffix to the wrapped API functions, as in

LLVMDIBuilderInsertDeclare_3_5(...)
LLVMDIBuilderInsertDeclare_3_6(...)

That way we would not have to put logic into the wrapper.

[michaelwoerister]

Hm, I'm getting strange runtime errors from code compiled with rustc built against LLVM 3.5.0 and 3.5.1:

error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'assertion failed: self.raw.hash != self.hashes_end', /home/mw/rust/src/libstd/collections/hash/table.rs:772

[sylvestre]

PR #21588 fixes this issue.

[michaelwoerister]

@sylvestre Thanks!
It seems though that this particular issue is still open: #21620

I will now focus on making everything compile with LLVM 3.5 and 3.6. Then everything should just work if the above issue gets fixed in a 3.5.2 release.

[lucab]

@michaelwoerister Feel free to cherry-pick the commits from that PR in your queue. It was not merged at that point as 3.5.1 won't work anyway. However, if we manage to get the fixes into a 3.5.2 and you are touching rustllvm anyway, I think it makes sense to include them and hope for the best.