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Commit 02c9460a authored by Andreas Gampe's avatar Andreas Gampe
Browse files

BitSet32 64b compatibility fix 

Using __builtin_c{l,t}zl fails on 64b systems as unsigned long is
8B there. However, unsigned int is only guaranteed to be 2B. Introduce
a check that should be optimized away by the compiler.

Change-Id: I854d0817c6bb5ae13c257241240664bf8f1a7c8a
parent e2acb82a

include/utils/BitSet.h

+22 −3
Original line number Diff line number Diff line
@@ -75,19 +75,19 @@ struct BitSet32 { 
    // Result is undefined if all bits are unmarked.

    inline uint32_t firstMarkedBit() const { return firstMarkedBit(value); }



    static uint32_t firstMarkedBit(uint32_t value) { return __builtin_clzl(value); }

    static uint32_t firstMarkedBit(uint32_t value) { return clz_checked(value); }



    // Finds the first unmarked bit in the set.

    // Result is undefined if all bits are marked.

    inline uint32_t firstUnmarkedBit() const { return firstUnmarkedBit(value); }



    static inline uint32_t firstUnmarkedBit(uint32_t value) { return __builtin_clzl(~ value); }

    static inline uint32_t firstUnmarkedBit(uint32_t value) { return clz_checked(~ value); }



    // Finds the last marked bit in the set.

    // Result is undefined if all bits are unmarked.

    inline uint32_t lastMarkedBit() const { return lastMarkedBit(value); }



    static inline uint32_t lastMarkedBit(uint32_t value) { return 31 - __builtin_ctzl(value); }

    static inline uint32_t lastMarkedBit(uint32_t value) { return 31 - ctz_checked(value); }



    // Finds the first marked bit in the set and clears it.  Returns the bit index.

    // Result is undefined if all bits are unmarked.
@@ -145,6 +145,25 @@ struct BitSet32 { 
        value |= other.value;

        return *this;

    }



private:

    // We use these helpers as the signature of __builtin_c{l,t}z has "unsigned int" for the

    // input, which is only guaranteed to be 16b, not 32. The compiler should optimize this away.

    static inline uint32_t clz_checked(uint32_t value) {

        if (sizeof(unsigned int) == sizeof(uint32_t)) {

            return __builtin_clz(value);

        } else {

            return __builtin_clzl(value);

        }

    }



    static inline uint32_t ctz_checked(uint32_t value) {

        if (sizeof(unsigned int) == sizeof(uint32_t)) {

            return __builtin_ctz(value);

        } else {

            return __builtin_ctzl(value);

        }

    }

};



ANDROID_BASIC_TYPES_TRAITS(BitSet32)