[LLVMbugs] [Bug 17405] New: DSE miscompile

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17405

            Bug ID: 17405
           Summary: DSE miscompile
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: hfinkel at anl.gov
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 11296
  --> http://llvm.org/bugs/attachment.cgi?id=11296&action=edit
bugpoint reduced test case (part to optimize)

I've used bugpoint to isolate a miscompile from DSE.

opt bugpoint-tooptimize.ll -basicaa -dse -S > bugpoint-tooptimize-opt.ll
clang bugpoint-tooptimize.ll bugpoint-tonotoptimize.ll -o /tmp/t1
clang bugpoint-tooptimize-opt.ll bugpoint-tonotoptimize.ll -o /tmp/t2

$ /tmp/t1
false
true
false
true
false
...

$ /tmp/t2
false
false
false
false
false
...

The only change that DSE is making is to remove 4 (apparently not all dead)
stores.

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