[LLVMbugs] [Bug 13042] New: incorrect optimization where i64 is converted to i192

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13042

             Bug #: 13042
           Summary: incorrect optimization where i64 is converted to i192
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: nmatsakis at mozilla.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 8690
  --> http://llvm.org/bugs/attachment.cgi?id=8690
bitcode demonstrating the problem

I am attaching a .bc file for a single function.  The unoptimized version
includes this code:

```
  %15 = bitcast %"enum parse::token::token[#0]"* %3 to { i64, i8 }*
  %16 = getelementptr inbounds { i64, i8 }* %15, i32 0, i32 0
  %17 = load i64* %16
  switch i64 %17, label %match_else28672 [
    i64 35, label %match_case28673
  ]
```

which is compiled into this code:

```
  %10 = bitcast i8* addrspace(1)* %9 to i192 addrspace(1)*
  %srcval = load i192 addrspace(1)* %10, align 1
  %11 = and i192 %srcval, 340282366920938463481821351505477763071
  %12 = icmp eq i192 %11, 35
  br i1 %12, label %call28676, label %case_body28671
```

It seems to me that the computation of %11 is incorrect.  It is masking with 
0x10000000000000000ffffffffffffffff but it ought to be masking with
0xffffffffffffffff.

(This is a little endian system)

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