[llvm-bugs] [Bug 49687] New: Infinite loop in a recursive call graph

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49687

            Bug ID: 49687
           Summary: Infinite loop in a recursive call graph
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: pctammela at gmail.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

Created attachment 24681
  --> https://bugs.llvm.org/attachment.cgi?id=24681&action=edit
Simplified IR found by bugpoint

I have a recursive call graph that is apparently entering an infinite
loop, at first I observed this when forcing inline in the optimization pipeline
but later bugpoint found a more concise pipeline that reproduces the bug.

Bugpoint found the following 'opt' invocation to enter the infinite loop:

   opt -inline -simplifycfg -tailcallelim -loop-unroll

As a comparison, the original C code when compiled with GCC and the
'alwaysinline' attribute errors out, for all optimizations, with the following:

   out.c: In function ‘__foo’:
   out.c:252:50: error: inlining failed in call to always_inline
   ‘__bar’: function not inlinable

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