[LLVMbugs] [Bug 3225] New: Wrong code legalizing 64-bit shift on x86

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Tue Dec 16 18:24:48 PST 2008


           Summary: Wrong code legalizing 64-bit shift on x86
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: sharparrow1 at yahoo.com
                CC: llvmbugs at cs.uiuc.edu

Created an attachment (id=2310)
 --> (http://llvm.org/bugs/attachment.cgi?id=2310)

Testcase attached; should print out "4294967295" when run, but currently prints
out "-1" on x86.

Roughly, the issue is that DAGTypeLegalizer::
ExpandShiftWithKnownAmountBit is generating an undefined shift.  This issue is
often not visible on x86 because it requires a shift by zero, and shldl hides
the issue; however, a carefully crafted testcase like the attached shows the

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