[LLVMbugs] [Bug 3489] New: misoptimization in presence of bitcast/memcpy

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=3489

           Summary: misoptimization in presence of bitcast/memcpy
           Product: new-bugs
           Version: unspecified
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: daniel at zuster.org
                CC: llvmbugs at cs.uiuc.edu


Created an attachment (id=2500)
 --> (http://llvm.org/bugs/attachment.cgi?id=2500)
input C file

The attached code is being misoptimized by LLVM; I suspect the problem is in
the constant folding of values accessed through the bitcast/memcpy done for ABI
purposes:
--
ddunbar at milton:CodeGen$ xcc -arch x86_64 -O0 bad.c -emit-llvm -o bad.bc
ddunbar at milton:CodeGen$ llc < bad.bc | gcc -x assembler -
ddunbar at milton:CodeGen$ ./a.out; echo $?
0
ddunbar at milton:CodeGen$ opt -std-compile-opts < bad.bc | llc | gcc -x assembler
-
ddunbar at milton:CodeGen$ ./a.out; echo $?
48
--


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