[llvm-bugs] [Bug 27610] New: failure to optimize side-effect free assembly

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=27610

            Bug ID: 27610
           Summary: failure to optimize side-effect free assembly
           Product: new-bugs
           Version: 3.8
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: superjoe30 at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

; ModuleID = 'test.ll'
; Question: why doesn't the following remove the body of derp?
; opt -O3 test.ll -print-module

@argv = internal unnamed_addr global i8** undef

; Function Attrs: nounwind
define void @derp() #0 {
entry:
  %0 = tail call i8** asm "lea 0x8(%rsp), $0", "=r"() #0
  store i8** %0, i8*** @argv, align 8
  ret void
}

attributes #0 = { nounwind }


Here, @argv is internal and never read. Therefore, the inline assembly and
entire body of the function should be optimized away.

Note that the inline assembly is *not* marked `sideeffect`.

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