[llvm-bugs] [Bug 33686] New: Infinite recursion in GlobalStatus called from -globalopt due to weird code in dead basic block

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=33686

            Bug ID: 33686
           Summary: Infinite recursion in GlobalStatus called from
                    -globalopt due to weird code in dead basic block
           Product: new-bugs
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: mikael.holmen at ericsson.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 18748
  --> https://bugs.llvm.org/attachment.cgi?id=18748&action=edit
reproducer

opt -globalopt -S -o - reduced.ll

causes

#0 0x0000000001f13e94 PrintStackTraceSignalHandler(void*)
(build-all-builtins/bin/opt+0x1f13e94)
#1 0x0000000001f14606 SignalHandler(int) (build-all-builtins/bin/opt+0x1f14606)
#2 0x00007faeb9926330 __restore_rt
(/lib/x86_64-linux-gnu/libpthread.so.0+0x10330)
#3 0x0000000001f639ff analyzeGlobalAux(llvm::Value const*, llvm::GlobalStatus&,
llvm::SmallPtrSetImpl<llvm::PHINode const*>&)
(build-all-builtins/bin/opt+0x1f639ff)
#4 0x0000000001f63c9e analyzeGlobalAux(llvm::Value const*, llvm::GlobalStatus&,
llvm::SmallPtrSetImpl<llvm::PHINode const*>&)
(build-all-builtins/bin/opt+0x1f63c9e)
#5 0x0000000001f63c9e analyzeGlobalAux(llvm::Value const*, llvm::GlobalStatus&,
llvm::SmallPtrSetImpl<llvm::PHINode const*>&)
(build-all-builtins/bin/opt+0x1f63c9e)
#6 0x0000000001f63c9e analyzeGlobalAux(llvm::Value const*, llvm::GlobalStatus&,
llvm::SmallPtrSetImpl<llvm::PHINode const*>&)
(build-all-builtins/bin/opt+0x1f63c9e)
#7 0x0000000001f63c9e analyzeGlobalAux(llvm::Value const*, llvm::GlobalStatus&,
llvm::SmallPtrSetImpl<llvm::PHINode const*>&)
(build-all-builtins/bin/opt+0x1f63c9e)
#8 0x0000000001f63c9e analyzeGlobalAux(llvm::Value const*, llvm::GlobalStatus&,
llvm::SmallPtrSetImpl<llvm::PHINode const*>&)
(build-all-builtins/bin/opt+0x1f63c9
[...]

Input program:

@g_127 = external global i16, align 1

define void @fn1() {
for.end5:
  ret void

for.cond1:                                        ; preds = %for.cond1
  %g_127.l_213.1 = select i1 undef, i16* @g_127, i16* %g_127.l_213.1
  br label %for.cond1
}

So for.cond1 isn't reachable from the and it contains a self-referencing
instruction that GlobalStatus::analyzeGlobal/analyzeGlobalAux recurses forever
on.

Should GlobalStatus handle this? Or should GlobalOpt remove dead basic blocks
before doing its stuff?

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