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Implement sk_atomic_conditional_inc with sk_atomic_cas.

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Now that we have sk_atomic_cas, we can replace all the platform-specific CAS loops with one.

BUG=skia:
R=bungeman@google.com, mtklein@google.com, reed@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/300553003

git-svn-id: http://skia.googlecode.com/svn/trunk@14892 2bbb7eff-a529-9590-31e7-b0007b416f81
This commit is contained in:
commit-bot@chromium.org 2014-05-27 15:00:32 +00:00
parent 29239a0f4b
commit 81da061f72
5 changed files with 15 additions and 59 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
include/core/SkThread.h
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@ -27,12 +27,6 @@ static int32_t sk_atomic_add(int32_t* addr, int32_t inc);
*/
static int32_t sk_atomic_dec(int32_t* addr);
/** Atomically adds one to the int referenced by addr iff the referenced int was not 0
* and returns the previous value.
* No additional memory barrier is required; this must act as a compiler barrier.
*/
static int32_t sk_atomic_conditional_inc(int32_t* addr);
/** Atomic compare and set.
* If *addr == before, set *addr to after and return true, otherwise return false.
* This must act as a release (SL/S) memory barrier and as a compiler barrier.
@ -51,6 +45,21 @@ static void sk_membar_acquire__after_atomic_conditional_inc();
#include SK_ATOMICS_PLATFORM_H
/** Atomically adds one to the int referenced by addr iff the referenced int was not 0
* and returns the previous value.
* No additional memory barrier is required; this must act as a compiler barrier.
*/
static inline int32_t sk_atomic_conditional_inc(int32_t* addr) {
int32_t prev;
do {
prev = *addr;
if (0 == prev) {
break;
}
} while (!sk_atomic_cas(addr, prev, prev+1));
return prev;
}
/** SK_MUTEX_PLATFORM_H must provide the following (or equivalent) declarations.
class SkBaseMutex {

12
src/ports/SkAtomics_android.h
View File

@ -32,18 +32,6 @@ static inline __attribute__((always_inline)) void sk_membar_acquire__after_atomi
//android_atomic_acquire_store(0, &dummy);
}
static inline __attribute__((always_inline)) int32_t sk_atomic_conditional_inc(int32_t* addr) {
while (true) {
int32_t value = *addr;
if (value == 0) {
return 0;
}
if (0 == android_atomic_release_cas(value, value + 1, addr)) {
return value;
}
}
}
static inline __attribute__((always_inline)) bool sk_atomic_cas(int32_t* addr,
int32_t before,
int32_t after) {

6
src/ports/SkAtomics_none.h
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@ -32,12 +32,6 @@ static inline int32_t sk_atomic_dec(int32_t* addr) {
static inline void sk_membar_acquire__after_atomic_dec() { }
static inline int32_t sk_atomic_conditional_inc(int32_t* addr) {
int32_t value = *addr;
if (value != 0) ++*addr;
return value;
}
static inline bool sk_atomic_cas(int32_t* addr, int32_t before, int32_t after) {
if (*addr != before) return false;
*addr = after;

18
src/ports/SkAtomics_sync.h
View File

@ -26,24 +26,6 @@ static inline __attribute__((always_inline)) int32_t sk_atomic_dec(int32_t* addr
static inline __attribute__((always_inline)) void sk_membar_acquire__after_atomic_dec() { }
static inline __attribute__((always_inline)) int32_t sk_atomic_conditional_inc(int32_t* addr) {
int32_t value = *addr;
while (true) {
if (value == 0) {
return 0;
}
int32_t before = __sync_val_compare_and_swap(addr, value, value + 1);
if (before == value) {
return value;
} else {
value = before;
}
}
}
static inline __attribute__((always_inline)) bool sk_atomic_cas(int32_t* addr,
int32_t before,
int32_t after) {

17
src/ports/SkAtomics_win.h
View File

@ -36,23 +36,6 @@ static inline int32_t sk_atomic_dec(int32_t* addr) {
static inline void sk_membar_acquire__after_atomic_dec() { }
static inline int32_t sk_atomic_conditional_inc(int32_t* addr) {
long value = *addr;
while (true) {
if (value == 0) {
return 0;
}
long before = _InterlockedCompareExchange(reinterpret_cast<long*>(addr), value + 1, value);
if (before == value) {
return value;
} else {
value = before;
}
}
}
static inline bool sk_atomic_cas(int32_t* addr, int32_t before, int32_t after) {
return _InterlockedCompareExchange(reinterpret_cast<long*>(addr), after, before) == before;
}