[llvm-commits] [LLVMbugs] [Bug 7322] ms vcpp build warnings

[Chris Lattner]

Nate, can you change these to use "nElts << (int)quad" or something?

-Chris

On Jun 15, 2010, at 7:43 AM, Dimitry Andric wrote:

> On 2010-06-14 22:39, bugzilla-daemon at llvm.org wrote:
>> --- Comment #1 from Chris Lattner <clattner at apple.com> 2010-06-14 15:39:27 CDT ---
>> there are a bunch of build warnings with MSVC.  If you're interested in helping
>> with this, please send patches to llvm-commits, thanks!
> 
> What I see quite often with VC++ is this warning:
> 
> .\NeonEmitter.cpp(529) : warning C4804: '<<' : unsafe use of type 'bool' in operation
> 
> which comes from bool variables used as shift count, e.g:
> 
>  bool dummy, quad = false;
> ...
>    b = Duplicate(nElts << quad, typestr, "b");
> 
> I'm not sure if this is unnecessarily paranoid of VC++, as the standard
> seems to imply it should be no problem, if I read it correctly:
> 
> [conv.prom]
> 4. An rvalue of type bool can be converted to an rvalue of type int,
>   with false becoming zero and true becoming one.
> 
> and [conv.integral]:
> 
> 4. If the destination type is bool, see 4.12. If the source type is
>   bool, the value false is converted to zero and the value true is
>   converted to one.
> 
> In short, is it worthwhile to appease VC++ here, by using an int or
> unsigned instead, or should we just stash in a pragma to disable this
> particular warning?
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