[llvm] r247972 - Simplify SmallBitVector::applyMask by consolidating common code for 32-bit and 64-bit builds.

[Yaron Keren via llvm-commits]

Thanks, this code will not be reached in 32 bits as the assert will fail
but that won't hold in release config, the shift code should probably be in
a conditional of both NumBaseBits and MaskWords, as was the original code.
It should be still possible to merge them but more carefully.


2015-09-18 15:20 GMT+03:00 Aaron Ballman <aaron at aaronballman.com>:

> On Fri, Sep 18, 2015 at 2:35 AM, Yaron Keren via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
> > Author: yrnkrn
> > Date: Fri Sep 18 01:35:12 2015
> > New Revision: 247972
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=247972&view=rev
> > Log:
> > Simplify SmallBitVector::applyMask by consolidating common code for
> 32-bit and 64-bit builds.
> > Extend mask value to 64 bits before taking its complement and assert
> when mask is
> > too large to apply in the small case (previously the extra words were
> silently ignored).
> >
> > http://reviews.llvm.org/D11890
> >
> > Patch by James Touton!
> >
> >
> > Modified:
> >     llvm/trunk/include/llvm/ADT/SmallBitVector.h
> >     llvm/trunk/unittests/ADT/BitVectorTest.cpp
> >
> > Modified: llvm/trunk/include/llvm/ADT/SmallBitVector.h
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/SmallBitVector.h?rev=247972&r1=247971&r2=247972&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/include/llvm/ADT/SmallBitVector.h (original)
> > +++ llvm/trunk/include/llvm/ADT/SmallBitVector.h Fri Sep 18 01:35:12 2015
> > @@ -553,17 +553,15 @@ public:
> >  private:
> >    template<bool AddBits, bool InvertMask>
> >    void applyMask(const uint32_t *Mask, unsigned MaskWords) {
> > -    if (NumBaseBits == 64 && MaskWords >= 2) {
> > -      uint64_t M = Mask[0] | (uint64_t(Mask[1]) << 32);
> > -      if (InvertMask) M = ~M;
> > -      if (AddBits) setSmallBits(getSmallBits() | M);
> > -      else         setSmallBits(getSmallBits() & ~M);
> > -    } else {
> > -      uint32_t M = Mask[0];
> > -      if (InvertMask) M = ~M;
> > -      if (AddBits) setSmallBits(getSmallBits() | M);
> > -      else         setSmallBits(getSmallBits() & ~M);
> > +    uintptr_t M = Mask[0];
> > +    if (MaskWords != 1) {
> > +      assert(NumBaseBits == 64 && MaskWords == 2 &&
> > +             "Mask is larger than base!");
> > +      M |= uintptr_t(Mask[1]) << 32;
>
> This patch introduces undefined behavior on platforms where uintptr_t
> is 32-bits, such as on Windows when compiling with MSVC in 23-bit
> mode.
>
> 67>E:\llvm\llvm\include\llvm/ADT/SmallBitVector.h(560): warning C4293:
> '<<': shift count negative or too big, undefined behavior (compiling
> source file
> E:\llvm\llvm\tools\clang\lib\StaticAnalyzer\Core\FunctionSummary.cpp)
> 67>  E:\llvm\llvm\include\llvm/ADT/SmallBitVector.h(521): note: see
> reference to function template instantiation 'void
> llvm::SmallBitVector::applyMask<true,false>(const uint32_t *,unsigned
> int)' being compiled (compiling source file
> E:\llvm\llvm\tools\clang\lib\StaticAnalyzer\Core\FunctionSummary.cpp)
>
> I am reverting the patch (and r247972) temporarily since this also
> generates a lot of warnings (everywhere SmallBitVector.h ends up being
> included from) in r247983.
>
> ~Aaron
>
> >      }
> > +    if (InvertMask) M = ~M;
> > +    if (AddBits) setSmallBits(getSmallBits() | M);
> > +    else         setSmallBits(getSmallBits() & ~M);
> >    }
> >  };
> >
> >
> > Modified: llvm/trunk/unittests/ADT/BitVectorTest.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/BitVectorTest.cpp?rev=247972&r1=247971&r2=247972&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/unittests/ADT/BitVectorTest.cpp (original)
> > +++ llvm/trunk/unittests/ADT/BitVectorTest.cpp Fri Sep 18 01:35:12 2015
> > @@ -235,12 +235,12 @@ TYPED_TEST(BitVectorTest, PortableBitMas
> >    const uint32_t Mask1[] = { 0x80000000, 6, 5 };
> >
> >    A.resize(10);
> > -  A.setBitsInMask(Mask1, 3);
> > +  A.setBitsInMask(Mask1, 2);
> >    EXPECT_EQ(10u, A.size());
> >    EXPECT_FALSE(A.test(0));
> >
> >    A.resize(32);
> > -  A.setBitsInMask(Mask1, 3);
> > +  A.setBitsInMask(Mask1, 2);
> >    EXPECT_FALSE(A.test(0));
> >    EXPECT_TRUE(A.test(31));
> >    EXPECT_EQ(1u, A.count());
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>
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