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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
This commit is contained in:
Andreas Gampe 2014-04-11 18:23:11 -07:00
parent e2acb82a94
commit 02c9460a0a
1 changed files with 22 additions and 3 deletions
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25
include/utils/BitSet.h
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@ -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)