LLVM ERROR: Undefined temporary symbol from llvm-bolt, no binary generated

[jshufro]

Invocation as
> sudo PATH=$PATH:build/bin build/bin/llvm-bolt cookiemonster -o cookiemonster.bolt reorder-blocks=cache+ -reorder-functions=hfsort+ -split-functions=3 -split-all-cold -split-eh -dyno-stats -update-debug-sections -data=perf.fdata

results in output

BOLT-INFO: first alloc address is 0x400000
BOLT-INFO: creating new program header table at address 0x4e00000, offset 0x4a00000
BOLT-INFO: enabling relocation mode
BOLT-INFO: forcing -jump-tables=move as PIC jump table was detected
BOLT-INFO: 704 functions out of 7668 simple functions (9.2%) have non-empty execution profile.
BOLT-INFO: 194 non-simple function(s) have profile.
BOLT-INFO: profile for 1 objects was ignored
BOLT-INFO: the input contains 348 (dynamic count : 498927) missed opportunities for macro-fusion optimization. Will fix instances on a hot path.
BOLT-INFO: removed 32 'repz' prefixes with estimated execution count of 0 times.
BOLT-INFO: UCE removed 1413 blocks and 26003 bytes of code.
BOLT-INFO: running hfsort+ for 709 functions
BOLT-INFO: program-wide dynostats after all optimizations before SCTC and FOP:

            34106516 : executed forward branches
             7414759 : taken forward branches
            15375720 : executed backward branches
             8358219 : taken backward branches
             4648654 : executed unconditional branches
            19960039 : all function calls
             7434182 : indirect calls
             6583156 : PLT calls
           377604140 : executed instructions
            92739869 : executed load instructions
            59455877 : executed store instructions
               28577 : taken jump table branches
            54130890 : total branches
            20421632 : taken branches
            33709258 : non-taken conditional branches
            15772978 : taken conditional branches
            49482236 : all conditional branches

            33780793 : executed forward branches (-1.0%)
             7267644 : taken forward branches (-2.0%)
            15375694 : executed backward branches (-0.0%)
             8358193 : taken backward branches (-0.0%)
             4346996 : executed unconditional branches (-6.5%)
            19781435 : all function calls (-0.9%)
             7434182 : indirect calls (=)
             6583156 : PLT calls (=)
           373937996 : executed instructions (-1.0%)
            91209281 : executed load instructions (-1.7%)
            59455774 : executed store instructions (-0.0%)
               28577 : taken jump table branches (=)
            53503483 : total branches (-1.2%)
            19972833 : taken branches (-2.2%)
            33530650 : non-taken conditional branches (-0.5%)
            15625837 : taken conditional branches (-0.9%)
            49156487 : all conditional branches (-0.7%)

BOLT-INFO: SCTC: patched 105 tail calls (104 forward) tail calls (1 backward) from a total of 105 while removing 0 double jumps and removing 74 basic blocks totalling 370 bytes of code. CTCs total execution count is 2 and the number of times CTCs are taken is 0.
LLVM ERROR: Undefined temporary symbol

I'm at a loss for what could cause this.

[jshufro]

Here's -v output around the failing section:

BOLT-INFO: Finished pass: print dyno-stats after optimizations
BOLT-INFO: Starting pass: simplify-conditional-tail-calls
BOLT-INFO: SCTC: patched 105 tail calls (104 forward) tail calls (1 backward) from a total of 105 while removing 0 double jumps and removing 74 basic blocks totalling 370 bytes of code. CTCs total execution count is 2 and the number of times CTCs are taken is 0.
BOLT-INFO: Finished pass: simplify-conditional-tail-calls
BOLT-INFO: Starting pass: aligner
BOLT-INFO: Finished pass: aligner
BOLT-INFO: Starting pass: reorder-data
BOLT-INFO: Finished pass: reorder-data
BOLT-INFO: Starting pass: finalize-functions
BOLT-INFO: Finished pass: finalize-functions
BOLT-INFO: Starting pass: frame-optimizer
BOLT-INFO: Finished pass: frame-optimizer
BOLT-INFO: Starting pass: alloc-combiner
BOLT-INFO: Finished pass: alloc-combiner
BOLT-INFO: Starting pass: inst-lowering
BOLT-INFO: Finished pass: inst-lowering
BOLT-INFO: Starting pass: lower-annotations
BOLT-INFO: Finished pass: lower-annotations
LLVM ERROR: Undefined temporary symbol

[jshufro]

Failing message looks to be emitted from ELFObjectWriter::computeSymbolTable

[maksfb]

It looks like you've hit a bug with our unreachable code elimination optimization. Thanks for reporting it! As a workaround, could you try to run BOLT with additional flags -eliminate-unreachable=0 -simplify-conditional-tail-calls=0?

[jshufro]

That looks to be a viable workaround- thanks!