Using both --enable-debug, --enable-optimization causes an assertion failure on build

[robertg]

If you do ./configure --enable-debug --enable-optimization, make will fail with:

rustc: x86_64-apple-darwin/stage1/lib/rustlib/x86_64-apple-darwin/lib/librustc
Assertion failed: (T == dwarf::DW_TAG_typedef || T == dwarf::DW_TAG_const_type || T == dwarf::DW_TAG_volatile_type || T == dwarf::DW_TAG_restrict_type || T == dwarf::DW_TAG_enumeration_type), function isUnsignedDIType, file /Users/rgawdzik/dev/rust/src/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp, line 525.
make: *** [x86_64-apple-darwin/stage1/lib/rustlib/x86_64-apple-darwin/lib/stamp.rustc] Abort trap: 6

Fails on both mac, linux on master. This error does not occur if you only use --enable-debug or --enable-optimization exclusively.

[emberian]

Repros for me as well, on:

CFG_LLVM_LINKAGE_FILE=/home/cmr/rust/build/x86_64-unknown-linux-gnu/rt/llvmdeps.rs LD_LIBRARY_PATH=/home/cmr/rust/build/x86_64-unknown-linux-gnu/stage1/lib:$LD_LIBRARY_PATH   x86_64-unknown-linux-gnu/stage1/bin/rustc --cfg stage1  -O --cfg rtopt -C debug-assertions=on -g -C prefer-dynamic --target=x86_64-unknown-linux-gnu  -D warnings -L "x86_64-unknown-linux-gnu/rt" -L "/home/cmr/rust/build/x86_64-unknown-linux-gnu/llvm/Release+Asserts/lib"    --out-dir x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/lib -C extra-filename=-d8ace771 ../src/librustc/lib.rs

[pnkfelix]

yes I can reproduce this locally as well (thought it was somehow related to my own branch, glad I checked against master as well...)

[pnkfelix]

This was injected by f9d4149 (PR #26025), an LLVM upgrade. (I identified this via bisection, though it is a pretty obvious candidate for the cause in hindsight.)

cc @alexcrichton @michaelwoerister

[pnkfelix]

backtrace from the assert under lldb on OS X : https://gist.github.com/pnkfelix/13851983520628197add

[pnkfelix]

(lldb) 
frame #5: 0x00000001030bdeed librustc_llvm-7e44814b.dylib`isUnsignedDIType(DD=0x00000001c0d18400, Ty=0x0000000189547d00) + 349 at DwarfUnit.cpp:522
   519          T == dwarf::DW_TAG_structure_type ||
   520          T == dwarf::DW_TAG_union_type)
   521        return true;
-> 522      assert(T == dwarf::DW_TAG_typedef || T == dwarf::DW_TAG_const_type ||
   523             T == dwarf::DW_TAG_volatile_type ||
   524             T == dwarf::DW_TAG_restrict_type ||
   525             T == dwarf::DW_TAG_enumeration_type);
(lldb) p T
(llvm::dwarf::Tag) $0 = DW_TAG_subroutine_type