http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50698
--- Comment #6 from vincenzo Innocente <vincenzo.innocente at cern dot ch>
2011-10-15 13:40:31 UTC ---
I now moved to a more realistic case that can be reduced to this:
void loop(float * x, int n) {
for (int i=0;i!=n; ++i)
x[i]=x[i+n]+x[i+2*n];
}
and it creates aliases even if the memory region are clearly disjoint:
(used gcc version 4.7.0 20111015 (experimental) (GCC) )
keep here or open an other "enhancement request"?
2: versioning for alias required: can't determine dependence between *D.2199_12
and *D.2195_8
2: mark for run-time aliasing test between *D.2199_12 and *D.2195_8
2: versioning for alias required: can't determine dependence between *D.2205_18
and *D.2195_8
2: mark for run-time aliasing test between *D.2205_18 and *D.2195_8
2: Vectorizing an unaligned access.
2: Vectorizing an unaligned access.
2: Vectorizing an unaligned access.
2: vect_model_load_cost: unaligned supported by hardware.
2: vect_model_load_cost: inside_cost = 2, outside_cost = 0 .
2: vect_model_load_cost: unaligned supported by hardware.
2: vect_model_load_cost: inside_cost = 2, outside_cost = 0 .
2: vect_model_simple_cost: inside_cost = 1, outside_cost = 0 .
2: vect_model_store_cost: unaligned supported by hardware.
2: vect_model_store_cost: inside_cost = 2, outside_cost = 0 .
2: cost model: Adding cost of checks for loop versioning aliasing.
2: cost model: epilogue peel iters set to vf/2 because loop iterations are
unknown .
2: Cost model analysis:
Vector inside of loop cost: 7
Vector outside of loop cost: 19
Scalar iteration cost: 4
Scalar outside cost: 1
prologue iterations: 0
epilogue iterations: 2
Calculated minimum iters for profitability: 7
2: Profitability threshold = 6
Vectorizing loop at Arena.cpp:2
2: Profitability threshold is 6 loop iterations.
2: create runtime check for data references *D.2199_12 and *D.2195_8
2: create runtime check for data references *D.2205_18 and *D.2195_8
2: created 2 versioning for alias checks.
2: LOOP VECTORIZED.
Arena.cpp:1: note: vectorized 1 loops in function.
