[LLVMbugs] [Bug 2856] New: x86_fp80 NaN constants emitted inconsistently

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=2856

           Summary: x86_fp80 NaN constants emitted inconsistently
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Keywords: miscompilation
          Severity: normal
          Priority: P2
         Component: Backend: X86
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: kamm-removethis at incasoftware.de
                CC: llvmbugs at cs.uiuc.edu


Created an attachment (id=2054)
 --> (http://llvm.org/bugs/attachment.cgi?id=2054)
test case

The compiling and executing the attached LLVM IR prints 

7FFF400000000
7FFFC00000000

even though the x86_fp80 constants used are identical
(0xK7FFF4000000000000000).

The relevant sections in the asm output are

the in-line constant (0x7FC00000):
.LCPI2_0:
        .long   2143289344      # float nan

the global (0x7FFF400000000000)
_D3nan4rvale:
        .size   _D3nan4rvale, 12
        .short  0       # long double least significant halfword of ~nan
        .short  0       # long double next halfword
        .short  0       # long double next halfword
        .short  16384   # long double next halfword
        .short  32767   # long double most significant halfword
        .zero   2

and they should describe the same value, but don't.


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