[llvm-bugs] [Bug 44215] New: D70157 "align branches within 32-Byte boundary" patch hangs on small assembly example

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=44215

            Bug ID: 44215
           Summary: D70157 "align branches within 32-Byte boundary" patch
                    hangs on small assembly example
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: fedor.v.sergeev at gmail.com
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, spatel+llvm at rotateright.com

Created attachment 22888
  --> https://bugs.llvm.org/attachment.cgi?id=22888&action=edit
hang-mc.s

I have been playing with https://reviews.llvm.org/D70157 patch and found a
problem with it.

It hangs in MCAssembler somewhere in vicinity of the new code.

] cd llvm-upstream/builds/release-assert
] bin/llvm-mc -x86-branches-within-32B-boundaries=true hang-mc.s -filetype=obj
-o /dev/null
....

when interrupting in debugger I get this backtrace:
#0  0x00007ffff4d43a5a in getFixedValue(llvm::MCMachineDependentFragment
const*) () from llvm-upstream/builds/release-assert/bin/../lib/libLLVM-10git.so
#1  0x00007ffff4d43cef in
llvm::MCAssembler::relaxMachineDependent(llvm::MCAsmLayout&,
llvm::MCMachineDependentFragment&) () from
llvm-upstream/builds/release-assert/bin/../lib/libLLVM-10git.so
#2  0x00007ffff4d445aa in
llvm::MCAssembler::layoutSectionOnce(llvm::MCAsmLayout&, llvm::MCSection&) ()
from llvm-upstream/builds/release-assert/bin/../lib/libLLVM-10git.so
#3  0x00007ffff4d446fa in llvm::MCAssembler::layoutOnce(llvm::MCAsmLayout&) ()
from llvm-upstream/builds/release-assert/bin/../lib/libLLVM-10git.so
#4  0x00007ffff4d42a1b in llvm::MCAssembler::layout(llvm::MCAsmLayout&) () from
llvm-upstream/builds/release-assert/bin/../lib/libLLVM-10git.so
#5  0x00007ffff4d4336e in llvm::MCAssembler::Finish() () from
.llvm-upstream/builds/release-assert/bin/../lib/libLLVM-10git.so
...

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