typedef int (*fde_compare_t) (struct object *, const fde *, const fde *);
+// The extractor functions compute the pointer values for a block of
+// fdes. The block processing hides the call overhead.
-/* This is a special mix of insertion sort and heap sort, optimized for
- the data sets that actually occur. They look like
- 101 102 103 127 128 105 108 110 190 111 115 119 125 160 126 129 130.
- I.e. a linearly increasing sequence (coming from functions in the text
- section), with additionally a few unordered elements (coming from functions
- in gnu_linkonce sections) whose values are higher than the values in the
- surrounding linear sequence (but not necessarily higher than the values
- at the end of the linear sequence!).
- The worst-case total run time is O(N) + O(n log (n)), where N is the
- total number of FDEs and n is the number of erratic ones. */
+static void
+fde_unencoded_extract (struct object *ob __attribute__ ((unused)),
+ _Unwind_Ptr *target, const fde **x, int count)
+{
+ for (int index = 0; index < count; ++index)
+ memcpy (target + index, x[index]->pc_begin, sizeof (_Unwind_Ptr));
+}
+
+static void
+fde_single_encoding_extract (struct object *ob, _Unwind_Ptr *target,
+ const fde **x, int count)
+{
+ _Unwind_Ptr base;
+
+ base = base_from_object (ob->s.b.encoding, ob);
+ for (int index = 0; index < count; ++index)
+ read_encoded_value_with_base (ob->s.b.encoding, base, x[index]->pc_begin,
+ target + index);
+}
+
+static void
+fde_mixed_encoding_extract (struct object *ob, _Unwind_Ptr *target,
+ const fde **x, int count)
+{
+ for (int index = 0; index < count; ++index)
+ {
+ int encoding = get_fde_encoding (x[index]);
+ read_encoded_value_with_base (encoding, base_from_object (encoding, ob),
+ x[index]->pc_begin, target + index);
+ }
+}
+
+typedef void (*fde_extractor_t) (struct object *, _Unwind_Ptr *, const fde **,
+ int);
+
+// Data is is sorted using radix sort if possible, using an temporary
+// auxiliary data structure of the same size as the input. When running
+// out of memory do in-place heap sort.
struct fde_accumulator
{
struct fde_vector *linear;
- struct fde_vector *erratic;
+ struct fde_vector *aux;
};
static inline int
if ((accu->linear = malloc (size)))
{
accu->linear->count = 0;
- if ((accu->erratic = malloc (size)))
- accu->erratic->count = 0;
+ if ((accu->aux = malloc (size)))
+ accu->aux->count = 0;
return 1;
}
else
accu->linear->array[accu->linear->count++] = this_fde;
}
-/* Split LINEAR into a linear sequence with low values and an erratic
- sequence with high values, put the linear one (of longest possible
- length) into LINEAR and the erratic one into ERRATIC. This is O(N).
-
- Because the longest linear sequence we are trying to locate within the
- incoming LINEAR array can be interspersed with (high valued) erratic
- entries. We construct a chain indicating the sequenced entries.
- To avoid having to allocate this chain, we overlay it onto the space of
- the ERRATIC array during construction. A final pass iterates over the
- chain to determine what should be placed in the ERRATIC array, and
- what is the linear sequence. This overlay is safe from aliasing. */
-
-static inline void
-fde_split (struct object *ob, fde_compare_t fde_compare,
- struct fde_vector *linear, struct fde_vector *erratic)
-{
- static const fde *marker;
- size_t count = linear->count;
- const fde *const *chain_end = ▮
- size_t i, j, k;
-
- /* This should optimize out, but it is wise to make sure this assumption
- is correct. Should these have different sizes, we cannot cast between
- them and the overlaying onto ERRATIC will not work. */
- gcc_assert (sizeof (const fde *) == sizeof (const fde **));
-
- for (i = 0; i < count; i++)
- {
- const fde *const *probe;
-
- for (probe = chain_end;
- probe != &marker && fde_compare (ob, linear->array[i], *probe) < 0;
- probe = chain_end)
- {
- chain_end = (const fde *const*) erratic->array[probe - linear->array];
- erratic->array[probe - linear->array] = NULL;
- }
- erratic->array[i] = (const fde *) chain_end;
- chain_end = &linear->array[i];
- }
-
- /* Each entry in LINEAR which is part of the linear sequence we have
- discovered will correspond to a non-NULL entry in the chain we built in
- the ERRATIC array. */
- for (i = j = k = 0; i < count; i++)
- if (erratic->array[i])
- linear->array[j++] = linear->array[i];
- else
- erratic->array[k++] = linear->array[i];
- linear->count = j;
- erratic->count = k;
-}
-
#define SWAP(x,y) do { const fde * tmp = x; x = y; y = tmp; } while (0)
/* Convert a semi-heap to a heap. A semi-heap is a heap except possibly
#undef SWAP
}
-/* Merge V1 and V2, both sorted, and put the result into V1. */
+// Radix sort data in V1 using V2 as aux memory. Runtime O(n).
static inline void
-fde_merge (struct object *ob, fde_compare_t fde_compare,
- struct fde_vector *v1, struct fde_vector *v2)
+fde_radixsort (struct object *ob, fde_extractor_t fde_extractor,
+ struct fde_vector *v1, struct fde_vector *v2)
{
- size_t i1, i2;
- const fde * fde2;
-
- i2 = v2->count;
- if (i2 > 0)
+#define FANOUTBITS 8
+#define FANOUT (1 << FANOUTBITS)
+#define BLOCKSIZE 128
+ const unsigned rounds
+ = (__CHAR_BIT__ * sizeof (_Unwind_Ptr) + FANOUTBITS - 1) / FANOUTBITS;
+ const fde **a1 = v1->array, **a2 = v2->array;
+ _Unwind_Ptr ptrs[BLOCKSIZE + 1];
+ unsigned n = v1->count;
+ for (unsigned round = 0; round != rounds; ++round)
{
- i1 = v1->count;
- do
+ unsigned counts[FANOUT] = {0};
+ unsigned violations = 0;
+
+ // Count the number of elements per bucket and check if we are already
+ // sorted.
+ _Unwind_Ptr last = 0;
+ for (unsigned i = 0; i < n;)
+ {
+ unsigned chunk = ((n - i) <= BLOCKSIZE) ? (n - i) : BLOCKSIZE;
+ fde_extractor (ob, ptrs + 1, a1 + i, chunk);
+ ptrs[0] = last;
+ for (unsigned j = 0; j < chunk; ++j)
+ {
+ unsigned b = (ptrs[j + 1] >> (round * FANOUTBITS)) & (FANOUT - 1);
+ counts[b]++;
+ // Use summation instead of an if to eliminate branches.
+ violations += ptrs[j + 1] < ptrs[j];
+ }
+ i += chunk;
+ last = ptrs[chunk];
+ }
+
+ // Stop if we are already sorted.
+ if (!violations)
+ {
+ // The sorted data is in a1 now.
+ a2 = a1;
+ break;
+ }
+
+ // Compute the prefix sum.
+ unsigned sum = 0;
+ for (unsigned i = 0; i != FANOUT; ++i)
+ {
+ unsigned s = sum;
+ sum += counts[i];
+ counts[i] = s;
+ }
+
+ // Place all elements.
+ for (unsigned i = 0; i < n;)
{
- i2--;
- fde2 = v2->array[i2];
- while (i1 > 0 && fde_compare (ob, v1->array[i1-1], fde2) > 0)
+ unsigned chunk = ((n - i) <= BLOCKSIZE) ? (n - i) : BLOCKSIZE;
+ fde_extractor (ob, ptrs, a1 + i, chunk);
+ for (unsigned j = 0; j < chunk; ++j)
{
- v1->array[i1+i2] = v1->array[i1-1];
- i1--;
+ unsigned b = (ptrs[j] >> (round * FANOUTBITS)) & (FANOUT - 1);
+ a2[counts[b]++] = a1[i + j];
}
- v1->array[i1+i2] = fde2;
+ i += chunk;
}
- while (i2 > 0);
- v1->count += v2->count;
+
+ // Swap a1 and a2.
+ const fde **tmp = a1;
+ a1 = a2;
+ a2 = tmp;
}
+#undef BLOCKSIZE
+#undef FANOUT
+#undef FANOUTBITS
+
+ // The data is in a2 now, move in place if needed.
+ if (a2 != v1->array)
+ memcpy (v1->array, a2, sizeof (const fde *) * n);
}
static inline void
end_fde_sort (struct object *ob, struct fde_accumulator *accu, size_t count)
{
- fde_compare_t fde_compare;
-
gcc_assert (!accu->linear || accu->linear->count == count);
- if (ob->s.b.mixed_encoding)
- fde_compare = fde_mixed_encoding_compare;
- else if (ob->s.b.encoding == DW_EH_PE_absptr)
- fde_compare = fde_unencoded_compare;
- else
- fde_compare = fde_single_encoding_compare;
-
- if (accu->erratic)
+ if (accu->aux)
{
- fde_split (ob, fde_compare, accu->linear, accu->erratic);
- gcc_assert (accu->linear->count + accu->erratic->count == count);
- frame_heapsort (ob, fde_compare, accu->erratic);
- fde_merge (ob, fde_compare, accu->linear, accu->erratic);
- free (accu->erratic);
+ fde_extractor_t fde_extractor;
+ if (ob->s.b.mixed_encoding)
+ fde_extractor = fde_mixed_encoding_extract;
+ else if (ob->s.b.encoding == DW_EH_PE_absptr)
+ fde_extractor = fde_unencoded_extract;
+ else
+ fde_extractor = fde_single_encoding_extract;
+
+ fde_radixsort (ob, fde_extractor, accu->linear, accu->aux);
+ free (accu->aux);
}
else
{
- /* We've not managed to malloc an erratic array,
+ fde_compare_t fde_compare;
+ if (ob->s.b.mixed_encoding)
+ fde_compare = fde_mixed_encoding_compare;
+ else if (ob->s.b.encoding == DW_EH_PE_absptr)
+ fde_compare = fde_unencoded_compare;
+ else
+ fde_compare = fde_single_encoding_compare;
+
+ /* We've not managed to malloc an aux array,
so heap sort in the linear one. */
frame_heapsort (ob, fde_compare, accu->linear);
}