[llvm] r233004 - Refactor: Simplify boolean expressions in llvm Support

[Kaylor, Andrew]

I wasn’t sure what to think of this one.  I guess it comes down to what the C++ standard says should be happening here.

At first glance, a bitwise XOR of a bool with something else seems sketchy.  On the other hand, if the standard promises to convert the rhs to bool before the ^= operation then the warning shouldn’t be there.

The C4805 warning seems to always apply to mixing bool with integer types.  It didn’t show up anywhere else in the llvm code base, so it doesn’t seem like disabling it across the board should be necessary.

-Andy


From: David Blaikie [mailto:dblaikie at gmail.com]
Sent: Monday, March 23, 2015 3:47 PM
To: Kaylor, Andrew
Cc: llvm-commits at cs.uiuc.edu
Subject: Re: [llvm] r233004 - Refactor: Simplify boolean expressions in llvm Support



On Mon, Mar 23, 2015 at 3:44 PM, Kaylor, Andrew <andrew.kaylor at intel.com<mailto:andrew.kaylor at intel.com>> wrote:
When I compile this with Visual Studio at /W4 I get this warning:

llvm\lib\Support\APFloat.cpp(1433): warning C4805: '^=' : unsafe mix of type 'bool' and type 'unsigned int' in operation

Is this worth warning on (Clang doesn't, for example) - should we just disable the MSVC warning, then?


According to the documentation this is a level 1 warning, so it probably appears with all builds.  I just happen to have been working on a change to enable W4 warnings on Windows.

-Andy


-----Original Message-----
From: llvm-commits-bounces at cs.uiuc.edu<mailto:llvm-commits-bounces at cs.uiuc.edu> [mailto:llvm-commits-bounces at cs.uiuc.edu<mailto:llvm-commits-bounces at cs.uiuc.edu>] On Behalf Of David Blaikie
Sent: Monday, March 23, 2015 12:46 PM
To: llvm-commits at cs.uiuc.edu<mailto:llvm-commits at cs.uiuc.edu>
Subject: [llvm] r233004 - Refactor: Simplify boolean expressions in llvm Support

Author: dblaikie
Date: Mon Mar 23 14:45:40 2015
New Revision: 233004

URL: http://llvm.org/viewvc/llvm-project?rev=233004&view=rev
Log:
Refactor: Simplify boolean expressions in llvm Support

Simplify boolean expressions using `true` and `false` with `clang-tidy`

Patch by Richard Thomson - I dropped the parens and != 0 test, for consistency with other patches/tests like this, but I'm open to the notion that we should add the explicit non-zero test in all these sort of cases (non-bool assigned to a bool).

Differential Revision: http://reviews.llvm.org/D8526

Modified:
    llvm/trunk/lib/Support/APFloat.cpp

Modified: llvm/trunk/lib/Support/APFloat.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/APFloat.cpp?rev=233004&r1=233003&r2=233004&view=diff
==============================================================================
--- llvm/trunk/lib/Support/APFloat.cpp (original)
+++ llvm/trunk/lib/Support/APFloat.cpp Mon Mar 23 14:45:40 2015
@@ -1430,7 +1430,7 @@ APFloat::addOrSubtractSignificand(const

   /* Determine if the operation on the absolute values is effectively
      an addition or subtraction.  */
-  subtract ^= (sign ^ rhs.sign) ? true : false;
+  subtract ^= sign ^ rhs.sign;

   /* Are we bigger exponent-wise than the RHS?  */
   bits = exponent - rhs.exponent;


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