[llvm] r247972 - Simplify SmallBitVector::applyMask by consolidating common code for 32-bit and 64-bit builds.
Yaron Keren via llvm-commits
llvm-commits at lists.llvm.org
Fri Sep 18 06:10:22 PDT 2015
I think this will work OK, will test:
void applyMask(const uint32_t *Mask, unsigned MaskWords) {
assert(MaskWords <= sizeof(uintptr_t) && "Mask is larger than base!");
uintptr_t M = Mask[0];
if (NumBaseBits == 64)
M |= uint64_t(Mask[1]) << 32;
if (InvertMask) M = ~M;
if (AddBits) setSmallBits(getSmallBits() | M);
else setSmallBits(getSmallBits() & ~M);
}
2015-09-18 16:02 GMT+03:00 Yaron Keren <yaron.keren at gmail.com>:
> The condition is on sizeof(uintptr_t) * CHAR_BIT which is a compile time
> constant. If it's not possible to make the same code work for both 32 and
> 64 bits without warnings it could be done with #ifdef (ugly) or template
> specialization for 32 and 64 bits where the unrequired version will not be
> instantiated.
>
>
> 2015-09-18 15:40 GMT+03:00 Aaron Ballman <aaron at aaronballman.com>:
>
>> On Fri, Sep 18, 2015 at 8:37 AM, Yaron Keren <yaron.keren at gmail.com>
>> wrote:
>> > 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.
>>
>> In theory, the code doesn't have to be reached for UB to cause
>> problems anyway. I wasn't certain that upcasting to 64-bits was the
>> right approach either, that's why I punted on just fixing it myself.
>> It still seems like it is solvable though.
>>
>> ~Aaron
>>
>> >
>> >
>> > 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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