[llvm-bugs] [Bug 31953] New: GVN miscompile

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=31953

            Bug ID: 31953
           Summary: GVN miscompile
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: mehdi.amini at apple.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 17975
  --> https://bugs.llvm.org/attachment.cgi?id=17975&action=edit
GVN bug test-case

I haven't been able to figure out why, but this is annoyingly miscompiling a
quite simple C++ file:


  $ opt -gvn  opt.before.gvn.bc  -o opt.bc && llc  opt.bc   -filetype=obj -o
opt.llc.o && clang opt.llc.o &&  ./a.out  | grep TEST2 
  …       oldCodeResult is INCORRECT


Without GVN:

  $ opt  opt.before.gvn.bc -o  opt.bc && llc  opt.bc   -filetype=obj -o
opt.llc.o && clang opt.llc.o &&  ./a.out  | grep TEST2 
  …       oldCodeResult is OK

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