From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 24660 invoked by alias); 10 May 2018 15:57:35 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 24534 invoked by uid 89); 10 May 2018 15:57:34 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-24.8 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,KAM_SHORT,SPF_PASS autolearn=ham version=3.3.2 spammy=mid, confine, assisting, (unknown) X-HELO: smtp.ispras.ru Received: from bran.ispras.ru (HELO smtp.ispras.ru) (83.149.199.196) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 10 May 2018 15:57:31 +0000 Received: from monopod.intra.ispras.ru (monopod.intra.ispras.ru [10.10.3.121]) by smtp.ispras.ru (Postfix) with ESMTP id 7ACAA22282; Thu, 10 May 2018 18:57:29 +0300 (MSK) From: Alexander Monakov To: gcc-patches@gcc.gnu.org Cc: Alexander Monakov Subject: [PATCH 1/2] gcc_qsort: source code changes Date: Thu, 10 May 2018 17:01:00 -0000 Message-Id: <20180510155641.2950-2-amonakov@ispras.ru> In-Reply-To: <20180510155641.2950-1-amonakov@ispras.ru> References: <20180510155641.2950-1-amonakov@ispras.ru> X-SW-Source: 2018-05/txt/msg00482.txt.bz2 * sort.cc: New file. * system.h [!CHECKING_P] (qsort): Redirect to gcc_qsort. * vec.c (qsort_chk): Use gcc_qsort. --- gcc/sort.cc | 232 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ gcc/system.h | 7 +- gcc/vec.c | 2 +- 3 files changed, 238 insertions(+), 3 deletions(-) create mode 100644 gcc/sort.cc diff --git a/gcc/sort.cc b/gcc/sort.cc new file mode 100644 index 00000000000..4faf6d45dc6 --- /dev/null +++ b/gcc/sort.cc @@ -0,0 +1,232 @@ +/* Platform-independent deterministic sort function. + Copyright (C) 2018 Free Software Foundation, Inc. + Contributed by Alexander Monakov. + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify it +under the terms of the GNU General Public License as published by the +Free Software Foundation; either version 3, or (at your option) any +later version. + +GCC is distributed in the hope that it will be useful, but WITHOUT +ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received a copy of the GNU General Public License +along with GCC; see the file COPYING3. If not see +. */ + +/* This implements a sort function suitable for GCC use cases: + - signature-compatible to C qsort, but relaxed contract: + - may apply the comparator to elements in a temporary buffer + - may abort on allocation failure + - deterministic (but not necessarily stable) + - fast, especially for common cases (0-5 elements of size 8 or 4) + + The implementation uses a network sort for up to 5 elements and + a merge sort on top of that. Neither stage has branches depending on + comparator result, trading extra arithmetic for branch mispredictions. */ + +#ifdef GENERATOR_FILE +#include "bconfig.h" +#else +#include "config.h" +#endif + +#include "system.h" + +#define likely(cond) __builtin_expect ((cond), 1) + +#ifdef __GNUC__ +#define noinline __attribute__ ((__noinline__)) +#else +#define noinline +#endif + +/* C-style qsort comparator function type. */ +typedef int cmp_fn (const void *, const void *); + +/* Structure holding read-mostly (read-only in netsort) context. */ +struct sort_ctx +{ + cmp_fn *cmp; // pointer to comparator + char *out; // output buffer + size_t n; // number of elements + size_t size; // element size +}; + +/* Helper for netsort. Permute, possibly in-place, 2 or 3 elements, + placing E0 to C->OUT, E1 to C->OUT + C->SIZE, and so on. */ +static void +reorder23 (sort_ctx *c, char *e0, char *e1, char *e2) +{ +#define REORDER_23(SIZE, STRIDE, OFFSET) \ +do { \ + size_t t0, t1; \ + memcpy (&t0, e0 + OFFSET, SIZE); \ + memcpy (&t1, e1 + OFFSET, SIZE); \ + char *out = c->out + OFFSET; \ + if (likely (c->n == 3)) \ + memcpy (out + 2*STRIDE, e2 + OFFSET, SIZE); \ + memcpy (out, &t0, SIZE); out += STRIDE; \ + memcpy (out, &t1, SIZE); \ +} while (0) + + if (sizeof (size_t) == 8 && likely (c->size == 8)) + REORDER_23 (8, 8, 0); + else if (likely (c->size == 4)) + REORDER_23 (4, 4, 0); + else + { + size_t offset = 0, step = sizeof (size_t); + for (; offset + step <= c->size; offset += step) + REORDER_23 (step, c->size, offset); + for (; offset < c->size; offset++) + REORDER_23 (1, c->size, offset); + } +} + +/* Like reorder23, but permute 4 or 5 elements. */ +static void +reorder45 (sort_ctx *c, char *e0, char *e1, char *e2, char *e3, char *e4) +{ +#define REORDER_45(SIZE, STRIDE, OFFSET) \ +do { \ + size_t t0, t1, t2, t3; \ + memcpy (&t0, e0 + OFFSET, SIZE); \ + memcpy (&t1, e1 + OFFSET, SIZE); \ + memcpy (&t2, e2 + OFFSET, SIZE); \ + memcpy (&t3, e3 + OFFSET, SIZE); \ + char *out = c->out + OFFSET; \ + if (likely (c->n == 5)) \ + memcpy (out + 4*STRIDE, e4 + OFFSET, SIZE); \ + memcpy (out, &t0, SIZE); out += STRIDE; \ + memcpy (out, &t1, SIZE); out += STRIDE; \ + memcpy (out, &t2, SIZE); out += STRIDE; \ + memcpy (out, &t3, SIZE); \ +} while (0) + + if (sizeof (size_t) == 8 && likely (c->size == 8)) + REORDER_45 (8, 8, 0); + else if (likely(c->size == 4)) + REORDER_45 (4, 4, 0); + else + { + size_t offset = 0, step = sizeof (size_t); + for (; offset + step <= c->size; offset += step) + REORDER_45 (step, c->size, offset); + for (; offset < c->size; offset++) + REORDER_45 (1, c->size, offset); + } +} + +/* Helper for netsort. Invoke comparator CMP on E0 and E1. + Return E0^E1 if E0 compares less than E1, zero otherwise. + This is noinline to avoid code growth and confine invocation + to a single call site, assisting indirect branch prediction. */ +noinline static intptr_t +cmp1 (char *e0, char *e1, cmp_fn *cmp) +{ + intptr_t x = (intptr_t)e0 ^ (intptr_t)e1; + return x & (cmp (e0, e1) >> 31); +} + +/* Execute network sort on 2 to 5 elements from IN, placing them into C->OUT. + IN may be equal to C->OUT, in which case elements are sorted in place. */ +static void +netsort (char *in, sort_ctx *c) +{ +#define CMP(e0, e1) \ +do { \ + intptr_t x = cmp1 (e1, e0, c->cmp); \ + e0 = (char *)((intptr_t)e0 ^ x); \ + e1 = (char *)((intptr_t)e1 ^ x); \ +} while (0) + + char *e0 = in, *e1 = e0 + c->size, *e2 = e1 + c->size; + CMP (e0, e1); + if (likely (c->n == 3)) + { + CMP (e1, e2); + CMP (e0, e1); + } + if (c->n <= 3) + return reorder23 (c, e0, e1, e2); + char *e3 = e2 + c->size, *e4 = e3 + c->size; + if (likely (c->n == 5)) + { + CMP (e3, e4); + CMP (e2, e4); + } + CMP (e2, e3); + if (likely (c->n == 5)) + { + CMP (e0, e3); + CMP (e1, e4); + } + CMP (e0, e2); + CMP (e1, e3); + CMP (e1, e2); + reorder45 (c, e0, e1, e2, e3, e4); +} + +/* Execute merge sort on N elements from IN, placing them into OUT, + using TMP as temporary storage if IN is equal to OUT. + This is a stable sort if netsort is used only for 2 or 3 elements. */ +static void +mergesort (char *in, sort_ctx *c, size_t n, char *out, char *tmp) +{ + if (likely (n <= 5)) + { + c->out = out; + c->n = n; + return netsort (in, c); + } + size_t nl = n / 2, nr = n - nl, sz = nl * c->size; + char *mid = in + sz, *r = out + sz, *l = in == out ? tmp : in; + /* Sort the right half, outputting to right half of OUT. */ + mergesort (mid, c, nr, r, tmp); + /* Sort the left half, leaving left half of OUT free. */ + mergesort (in, c, nl, l, mid); + /* Merge sorted halves given by L, R to [OUT, END). */ +#define MERGE_ELTSIZE(SIZE) \ +do { \ + intptr_t mr = c->cmp (r, l) >> 31; \ + intptr_t lr = (intptr_t)l ^ (intptr_t)r; \ + lr = (intptr_t)l ^ (lr & mr); \ + out = (char *)memcpy (out, (char *)lr, SIZE); \ + out += SIZE; \ + r += mr & SIZE; \ + if (r == out) return; \ + l += ~mr & SIZE; \ +} while (r != end) + + if (likely (c->cmp(r, l + (r - out) - c->size) < 0)) + { + char *end = out + n * c->size; + if (sizeof (size_t) == 8 && likely (c->size == 8)) + MERGE_ELTSIZE (8); + else if (likely (c->size == 4)) + MERGE_ELTSIZE (4); + else + MERGE_ELTSIZE (c->size); + } + memcpy (out, l, r - out); +} + +void +gcc_qsort (void *vbase, size_t n, size_t size, cmp_fn *cmp) +{ + if (n < 2) + return; + char *base = (char *)vbase; + sort_ctx c = {cmp, base, n, size}; + long long scratch[32]; + size_t bufsz = (n / 2) * size; + void *buf = bufsz <= sizeof scratch ? scratch : xmalloc (bufsz); + mergesort (base, &c, n, base, (char *)buf); + if (buf != scratch) + free (buf); +} diff --git a/gcc/system.h b/gcc/system.h index 4abc321c71d..88dffccb8ab 100644 --- a/gcc/system.h +++ b/gcc/system.h @@ -1202,11 +1202,14 @@ helper_const_non_const_cast (const char *p) /* qsort comparator consistency checking: except in release-checking compilers, redirect 4-argument qsort calls to qsort_chk; keep 1-argument invocations corresponding to vec::qsort (cmp): they use C qsort internally anyway. */ -#if CHECKING_P +void qsort_chk (void *, size_t, size_t, int (*)(const void *, const void *)); +void gcc_qsort (void *, size_t, size_t, int (*)(const void *, const void *)); #define PP_5th(a1, a2, a3, a4, a5, ...) a5 #undef qsort +#if CHECKING_P #define qsort(...) PP_5th (__VA_ARGS__, qsort_chk, 3, 2, qsort, 0) (__VA_ARGS__) -void qsort_chk (void *, size_t, size_t, int (*)(const void *, const void *)); +#else +#define qsort(...) PP_5th (__VA_ARGS__, gcc_qsort, 3, 2, qsort, 0) (__VA_ARGS__) #endif #endif /* ! GCC_SYSTEM_H */ diff --git a/gcc/vec.c b/gcc/vec.c index 11924a80a2d..2941715a34a 100644 --- a/gcc/vec.c +++ b/gcc/vec.c @@ -215,7 +215,7 @@ void qsort_chk (void *base, size_t n, size_t size, int (*cmp)(const void *, const void *)) { - (qsort) (base, n, size, cmp); + gcc_qsort (base, n, size, cmp); #if 0 #define LIM(n) (n) #else -- 2.13.3