[LLVMbugs] [Bug 3501] New: clang x86-64 ABI bug with bit-fields

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Fri Feb 6 19:41:53 PST 2009


           Summary: clang x86-64 ABI bug with bit-fields
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: LLVM Codegen
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: sharparrow1 at yahoo.com
                CC: llvmbugs at cs.uiuc.edu, daniel at zuster.org

unsigned a(struct {int a : 5, b : 5;} x) { return x.a; }

gcc asm:
        sall    $3, %edi
        sarb    $3, %dil
        movsbl  %dil,%eax

clang asm:
        movl    8(%rsp), %eax
        shll    $27, %eax
        sarl    $27, %eax

I know this stuff is very much in flux, but it's a relatively tricky case, so I
figured it was worth filing so it doesn't get lost.

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