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Fix stride decrease check for negative strides #415

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Fix stride decrease check for negative strides #415

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23 changes: 18 additions & 5 deletions kernel/tensor4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -72,16 +72,29 @@ int X(tensor_inplace_strides2)(const tensor *a, const tensor *b)
return X(tensor_inplace_strides(a)) && X(tensor_inplace_strides(b));
}

/* return true (1) iff *any* strides of sz decrease when we
tensor_inplace_copy(sz, k). */
/* Compare strides by magnitude first, using the signed value to distinguish
opposite traversal directions with equal magnitude. */
static int stride_lt(INT a, INT b)
{
INT aa = X(iabs)(a);
INT ab = X(iabs)(b);

return aa < ab || (aa == ab && a < b);
}

/* Return true (1) iff any stride of sz decreases in the magnitude-first
order when we tensor_inplace_copy(sz, k). */
static int tensor_strides_decrease(const tensor *sz, inplace_kind k)
{
if (FINITE_RNK(sz->rnk)) {
int i;
for (i = 0; i < sz->rnk; ++i)
if ((sz->dims[i].os - sz->dims[i].is)
* (k == INPLACE_OS ? (INT)1 : (INT)-1) < 0)
for (i = 0; i < sz->rnk; ++i) {
const iodim *p = sz->dims + i;
if (k == INPLACE_OS
? stride_lt(p->os, p->is)
: stride_lt(p->is, p->os))
return 1;
}
}
return 0;
}
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