diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c index 3c0cc654ec0..8d2eaaa6bc4 100644 --- a/libgcc/unwind-dw2-fde.c +++ b/libgcc/unwind-dw2-fde.c @@ -456,22 +456,52 @@ fde_mixed_encoding_compare (struct object *ob, const fde *x, const fde *y) 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 @@ -485,8 +515,8 @@ start_fde_sort (struct fde_accumulator *accu, size_t count) 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 @@ -500,59 +530,6 @@ fde_insert (struct fde_accumulator *accu, const fde *this_fde) 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 @@ -615,59 +592,116 @@ frame_heapsort (struct object *ob, fde_compare_t fde_compare, #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;) { - 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 + 1, a1 + i, chunk); + ptrs[0] = last; + for (unsigned j = 0; j < chunk; ++j) { - v1->array[i1+i2] = v1->array[i1-1]; - i1--; + 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]; } - v1->array[i1+i2] = fde2; + i += chunk; + last = ptrs[chunk]; } - while (i2 > 0); - v1->count += v2->count; + + // 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;) + { + unsigned chunk = ((n - i) <= BLOCKSIZE) ? (n - i) : BLOCKSIZE; + fde_extractor (ob, ptrs, a1 + i, chunk); + for (unsigned j = 0; j < chunk; ++j) + { + unsigned b = (ptrs[j] >> (round * FANOUTBITS)) & (FANOUT - 1); + a2[counts[b]++] = a1[i + j]; + } + i += chunk; + } + + // 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); }