[LLVMbugs] [Bug 5130] New: missed check for NULL and wrong value in structure

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=5130

           Summary: missed check for NULL and wrong value in structure
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: FreeBSD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: LLVM Codegen
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: rdivacky at freebsd.org
                CC: llvmbugs at cs.uiuc.edu


we see miscompilation of FreeBSD kernel with TOT llvm/clang

the attached test case is basically this code:

static struct taskqueue *
_taskqueue_create(const char *name, int mflags,
                 taskqueue_enqueue_fn enqueue, void *context,
                 int mtxflags, const char *mtxname)
{
        struct taskqueue *queue;

        queue = malloc(sizeof(struct taskqueue), M_TASKQUEUE, mflags | M_ZERO);
(1)     if (!queue)
                return NULL;

        STAILQ_INIT(&queue->tq_queue);
        queue->tq_name = name;
        queue->tq_enqueue = enqueue;
        queue->tq_context = context;
        queue->tq_spin = (mtxflags & MTX_SPIN) != 0;
(2)     queue->tq_flags |= TQ_FLAGS_ACTIVE;
        mtx_init(&queue->tq_mutex, mtxname, NULL, mtxflags);

        return queue;
}

there are two miscompilations on amd64 (and I think on i386 too). (the
generated asm attached)

1) there is a check for queue being NULL at (1) which is ommited in the
generated asm

2) the code at (2) is 


        return queue;
}

there are two miscompilations on amd64 (and I think on i386 too). (the
generated asm attached)

1) there is a check for queue being NULL at (1) which is ommited in the
generated asm

2) the code at (2) is 

         queue->tq_spin = (mtxflags & 0x00000001) != 0;

gcc generates this code:

        orl     $1, 96(%rbx)

while clang/llvm generates

        movl    $-1, 96(%r13)


these bugs are quite recent as I recall compiling a running FreeBSD kernel as
of roughly 2 weeks ago.


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