[kbuild-all] Re: [PATCH] lib/bch:using swap() instead of tmp variable

Hi Yihao, Thank you for the patch! Yet something to improve: [auto build test ERROR on linus/master] [also build test ERROR on v5.15 next-20211110] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Yihao-Han/lib-bch-using-swap-ins... base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git d2f38a3c6507b2520101f9a3807ed98f1bdc545a config: arc-allyesconfig (attached as .config) compiler: arceb-elf-gcc (GCC) 11.2.0 reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # https://github.com/0day-ci/linux/commit/67120a42a5dc4e4a08d998ae4dc41d9bf... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Yihao-Han/lib-bch-using-swap-instead-of-tmp-variable/20211109-143502 git checkout 67120a42a5dc4e4a08d998ae4dc41d9bf31946b5 # save the attached .config to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=arc SHELL=/bin/bash If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): lib/bch.c: In function 'solve_linear_system': 525 | tmp = rows[p]; | ^~~ | tm lib/bch.c:525:25: note: each undeclared identifier is reported only once for each function it appears in vim +525 lib/bch.c 437aa565e265677 Ivan Djelic 2011-03-11 494 437aa565e265677 Ivan Djelic 2011-03-11 495 /* 437aa565e265677 Ivan Djelic 2011-03-11 496 * solve a m x m linear system in GF(2) with an expected number of solutions, 437aa565e265677 Ivan Djelic 2011-03-11 497 * and return the number of found solutions 437aa565e265677 Ivan Djelic 2011-03-11 498 */ 437aa565e265677 Ivan Djelic 2011-03-11 499 static int solve_linear_system(struct bch_control *bch, unsigned int *rows, 437aa565e265677 Ivan Djelic 2011-03-11 500 unsigned int *sol, int nsol) 437aa565e265677 Ivan Djelic 2011-03-11 501 { 437aa565e265677 Ivan Djelic 2011-03-11 502 const int m = GF_M(bch); 67120a42a5dc4e4 Yihao Han 2021-11-08 503 unsigned int mask; 02361bc7788852f Kees Cook 2018-05-31 504 int rem, c, r, p, k, param[BCH_MAX_M]; 437aa565e265677 Ivan Djelic 2011-03-11 505 437aa565e265677 Ivan Djelic 2011-03-11 506 k = 0; 437aa565e265677 Ivan Djelic 2011-03-11 507 mask = 1 << m; 437aa565e265677 Ivan Djelic 2011-03-11 508 437aa565e265677 Ivan Djelic 2011-03-11 509 /* Gaussian elimination */ 437aa565e265677 Ivan Djelic 2011-03-11 510 for (c = 0; c < m; c++) { 437aa565e265677 Ivan Djelic 2011-03-11 511 rem = 0; 437aa565e265677 Ivan Djelic 2011-03-11 512 p = c-k; 437aa565e265677 Ivan Djelic 2011-03-11 513 /* find suitable row for elimination */ 437aa565e265677 Ivan Djelic 2011-03-11 514 for (r = p; r < m; r++) { 437aa565e265677 Ivan Djelic 2011-03-11 515 if (rows[r] & mask) { 437aa565e265677 Ivan Djelic 2011-03-11 516 if (r != p) { 67120a42a5dc4e4 Yihao Han 2021-11-08 517 swap(rows[r], rows[p]); 437aa565e265677 Ivan Djelic 2011-03-11 518 } 437aa565e265677 Ivan Djelic 2011-03-11 519 rem = r+1; 437aa565e265677 Ivan Djelic 2011-03-11 520 break; 437aa565e265677 Ivan Djelic 2011-03-11 521 } 437aa565e265677 Ivan Djelic 2011-03-11 522 } 437aa565e265677 Ivan Djelic 2011-03-11 523 if (rem) { 437aa565e265677 Ivan Djelic 2011-03-11 524 /* perform elimination on remaining rows */ 437aa565e265677 Ivan Djelic 2011-03-11 @525 tmp = rows[p]; 437aa565e265677 Ivan Djelic 2011-03-11 526 for (r = rem; r < m; r++) { 437aa565e265677 Ivan Djelic 2011-03-11 527 if (rows[r] & mask) 437aa565e265677 Ivan Djelic 2011-03-11 528 rows[r] ^= tmp; 437aa565e265677 Ivan Djelic 2011-03-11 529 } 437aa565e265677 Ivan Djelic 2011-03-11 530 } else { 437aa565e265677 Ivan Djelic 2011-03-11 531 /* elimination not needed, store defective row index */ 437aa565e265677 Ivan Djelic 2011-03-11 532 param[k++] = c; 437aa565e265677 Ivan Djelic 2011-03-11 533 } 437aa565e265677 Ivan Djelic 2011-03-11 534 mask >>= 1; 437aa565e265677 Ivan Djelic 2011-03-11 535 } 437aa565e265677 Ivan Djelic 2011-03-11 536 /* rewrite system, inserting fake parameter rows */ 437aa565e265677 Ivan Djelic 2011-03-11 537 if (k > 0) { 437aa565e265677 Ivan Djelic 2011-03-11 538 p = k; 437aa565e265677 Ivan Djelic 2011-03-11 539 for (r = m-1; r >= 0; r--) { 437aa565e265677 Ivan Djelic 2011-03-11 540 if ((r > m-1-k) && rows[r]) 437aa565e265677 Ivan Djelic 2011-03-11 541 /* system has no solution */ 437aa565e265677 Ivan Djelic 2011-03-11 542 return 0; 437aa565e265677 Ivan Djelic 2011-03-11 543 437aa565e265677 Ivan Djelic 2011-03-11 544 rows[r] = (p && (r == param[p-1])) ? 437aa565e265677 Ivan Djelic 2011-03-11 545 p--, 1u << (m-r) : rows[r-p]; 437aa565e265677 Ivan Djelic 2011-03-11 546 } 437aa565e265677 Ivan Djelic 2011-03-11 547 } 437aa565e265677 Ivan Djelic 2011-03-11 548 437aa565e265677 Ivan Djelic 2011-03-11 549 if (nsol != (1 << k)) 437aa565e265677 Ivan Djelic 2011-03-11 550 /* unexpected number of solutions */ 437aa565e265677 Ivan Djelic 2011-03-11 551 return 0; 437aa565e265677 Ivan Djelic 2011-03-11 552 437aa565e265677 Ivan Djelic 2011-03-11 553 for (p = 0; p < nsol; p++) { 437aa565e265677 Ivan Djelic 2011-03-11 554 /* set parameters for p-th solution */ 437aa565e265677 Ivan Djelic 2011-03-11 555 for (c = 0; c < k; c++) 437aa565e265677 Ivan Djelic 2011-03-11 556 rows[param[c]] = (rows[param[c]] & ~1)|((p >> c) & 1); 437aa565e265677 Ivan Djelic 2011-03-11 557 437aa565e265677 Ivan Djelic 2011-03-11 558 /* compute unique solution */ 437aa565e265677 Ivan Djelic 2011-03-11 559 tmp = 0; 437aa565e265677 Ivan Djelic 2011-03-11 560 for (r = m-1; r >= 0; r--) { 437aa565e265677 Ivan Djelic 2011-03-11 561 mask = rows[r] & (tmp|1); 437aa565e265677 Ivan Djelic 2011-03-11 562 tmp |= parity(mask) << (m-r); 437aa565e265677 Ivan Djelic 2011-03-11 563 } 437aa565e265677 Ivan Djelic 2011-03-11 564 sol[p] = tmp >> 1; 437aa565e265677 Ivan Djelic 2011-03-11 565 } 437aa565e265677 Ivan Djelic 2011-03-11 566 return nsol; 437aa565e265677 Ivan Djelic 2011-03-11 567 } 437aa565e265677 Ivan Djelic 2011-03-11 568 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org