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Improve performance of global atomics, taking advantage of associativity.

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For associative atomic ops (add, and, or, xor), we can take advantage of
their associativity to do just a single hardware atomic instruction, 
rather than one for each of the running program instances (as the previous
implementation did.)

The basic approach is to locally compute a reduction across the active
program instances with the given op and to then issue a single HW atomic
with that reduced value as the operand.  We then take the old value that
was stored in the location that is returned from the HW atomic op and
use that to compute the values to return to each of the program instances
(conceptually representing the cumulative effect of each of the preceding
program instances having performed their atomic operation.)

Issue #56.
This commit is contained in:
Matt Pharr
2011-08-31 05:35:01 -07:00
parent 96a297c747
commit e144724979
8 changed files with 224 additions and 38 deletions
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56
stdlib.ispc
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@@ -575,10 +575,10 @@ static inline void memory_barrier() {
__memory_barrier();
}
#define DEFINE_ATOMIC_OP(TA,TB,OPA,OPB) \
#define DEFINE_ATOMIC_OP(TA,TB,OPA,OPB,MASKTYPE) \
static inline TA atomic_##OPA##_global(uniform reference TA ref, TA value) { \
memory_barrier(); \
TA ret = __atomic_##OPB##_##TB##_global(ref, value, __mask); \
TA ret = __atomic_##OPB##_##TB##_global(ref, value, (MASKTYPE)__mask); \
memory_barrier(); \
return ret; \
}
@@ -595,49 +595,49 @@ static inline TA atomic_##OPA##_global(uniform reference TA ref, TA value) { \
return ret; \
}
DEFINE_ATOMIC_OP(int32,int32,add,add)
DEFINE_ATOMIC_OP(int32,int32,subtract,sub)
DEFINE_ATOMIC_OP(int32,int32,add,add,int32)
DEFINE_ATOMIC_OP(int32,int32,subtract,sub,int32)
DEFINE_ATOMIC_MINMAX_OP(int32,int32,min,min)
DEFINE_ATOMIC_MINMAX_OP(int32,int32,max,max)
DEFINE_ATOMIC_OP(int32,int32,and,and)
DEFINE_ATOMIC_OP(int32,int32,or,or)
DEFINE_ATOMIC_OP(int32,int32,xor,xor)
DEFINE_ATOMIC_OP(int32,int32,swap,swap)
DEFINE_ATOMIC_OP(int32,int32,and,and,int32)
DEFINE_ATOMIC_OP(int32,int32,or,or,int32)
DEFINE_ATOMIC_OP(int32,int32,xor,xor,int32)
DEFINE_ATOMIC_OP(int32,int32,swap,swap,int32)
// For everything but atomic min and max, we can use the same
// implementations for unsigned as for signed.
DEFINE_ATOMIC_OP(unsigned int32,int32,add,add)
DEFINE_ATOMIC_OP(unsigned int32,int32,subtract,sub)
DEFINE_ATOMIC_OP(unsigned int32,int32,add,add,int32)
DEFINE_ATOMIC_OP(unsigned int32,int32,subtract,sub,int32)
DEFINE_ATOMIC_MINMAX_OP(unsigned int32,uint32,min,umin)
DEFINE_ATOMIC_MINMAX_OP(unsigned int32,uint32,max,umax)
DEFINE_ATOMIC_OP(unsigned int32,int32,and,and)
DEFINE_ATOMIC_OP(unsigned int32,int32,or,or)
DEFINE_ATOMIC_OP(unsigned int32,int32,xor,xor)
DEFINE_ATOMIC_OP(unsigned int32,int32,swap,swap)
DEFINE_ATOMIC_OP(unsigned int32,int32,and,and,int32)
DEFINE_ATOMIC_OP(unsigned int32,int32,or,or,int32)
DEFINE_ATOMIC_OP(unsigned int32,int32,xor,xor,int32)
DEFINE_ATOMIC_OP(unsigned int32,int32,swap,swap,int32)
DEFINE_ATOMIC_OP(float,float,swap,swap)
DEFINE_ATOMIC_OP(float,float,swap,swap,int32)
DEFINE_ATOMIC_OP(int64,int64,add,add)
DEFINE_ATOMIC_OP(int64,int64,subtract,sub)
DEFINE_ATOMIC_OP(int64,int64,add,add,int64)
DEFINE_ATOMIC_OP(int64,int64,subtract,sub,int64)
DEFINE_ATOMIC_MINMAX_OP(int64,int64,min,min)
DEFINE_ATOMIC_MINMAX_OP(int64,int64,max,max)
DEFINE_ATOMIC_OP(int64,int64,and,and)
DEFINE_ATOMIC_OP(int64,int64,or,or)
DEFINE_ATOMIC_OP(int64,int64,xor,xor)
DEFINE_ATOMIC_OP(int64,int64,swap,swap)
DEFINE_ATOMIC_OP(int64,int64,and,and,int64)
DEFINE_ATOMIC_OP(int64,int64,or,or,int64)
DEFINE_ATOMIC_OP(int64,int64,xor,xor,int64)
DEFINE_ATOMIC_OP(int64,int64,swap,swap,int32)
// For everything but atomic min and max, we can use the same
// implementations for unsigned as for signed.
DEFINE_ATOMIC_OP(unsigned int64,int64,add,add)
DEFINE_ATOMIC_OP(unsigned int64,int64,subtract,sub)
DEFINE_ATOMIC_OP(unsigned int64,int64,add,add,int64)
DEFINE_ATOMIC_OP(unsigned int64,int64,subtract,sub,int64)
DEFINE_ATOMIC_MINMAX_OP(unsigned int64,uint64,min,umin)
DEFINE_ATOMIC_MINMAX_OP(unsigned int64,uint64,max,umax)
DEFINE_ATOMIC_OP(unsigned int64,int64,and,and)
DEFINE_ATOMIC_OP(unsigned int64,int64,or,or)
DEFINE_ATOMIC_OP(unsigned int64,int64,xor,xor)
DEFINE_ATOMIC_OP(unsigned int64,int64,swap,swap)
DEFINE_ATOMIC_OP(unsigned int64,int64,and,and,int64)
DEFINE_ATOMIC_OP(unsigned int64,int64,or,or,int64)
DEFINE_ATOMIC_OP(unsigned int64,int64,xor,xor,int64)
DEFINE_ATOMIC_OP(unsigned int64,int64,swap,swap,int32)
DEFINE_ATOMIC_OP(double,double,swap,swap)
DEFINE_ATOMIC_OP(double,double,swap,swap,int32)
#undef DEFINE_ATOMIC_OP