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From: "kristerw at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/106513] New: bswap is incorrectly generated Date: Wed, 03 Aug 2022 11:56:49 +0000 [thread overview] Message-ID: <bug-106513-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106513 Bug ID: 106513 Summary: bswap is incorrectly generated Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: kristerw at gcc dot gnu.org Target Milestone: --- GCC may incorrectly generate bswap instructions for code not doing a correct swap. This can be seen by running the function from testsuite/gcc.dg/pr40501.c as typedef long int int64_t; __attribute__((noinline)) int64_t swap64 (int64_t n) { return (((n & (((int64_t) 0xff) )) << 56) | ((n & (((int64_t) 0xff) << 8)) << 40) | ((n & (((int64_t) 0xff) << 16)) << 24) | ((n & (((int64_t) 0xff) << 24)) << 8) | ((n & (((int64_t) 0xff) << 32)) >> 8) | ((n & (((int64_t) 0xff) << 40)) >> 24) | ((n & (((int64_t) 0xff) << 48)) >> 40) | ((n & (((int64_t) 0xff) << 56)) >> 56)); } int main (void) { volatile int64_t n = 0x8000000000000000l; if (swap64(n) != 0xffffffffffffff80l) __builtin_abort (); return 0; } This fails at -Os and higher optimization levels.
next reply other threads:[~2022-08-03 11:56 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-08-03 11:56 kristerw at gcc dot gnu.org [this message] 2022-08-03 12:12 ` [Bug tree-optimization/106513] " schwab@linux-m68k.org 2022-08-03 12:41 ` kristerw at gcc dot gnu.org 2022-08-05 22:15 ` [Bug tree-optimization/106513] [10/11/12/13 Regression] bswap pass misses that >>56 for signed types can be replicate the sign bit pinskia at gcc dot gnu.org 2022-08-10 13:43 ` rguenth at gcc dot gnu.org 2022-08-10 13:51 ` rguenth at gcc dot gnu.org 2022-08-10 14:39 ` cvs-commit at gcc dot gnu.org 2022-08-10 14:40 ` cvs-commit at gcc dot gnu.org 2022-10-11 13:04 ` [Bug tree-optimization/106513] [10/11 " cvs-commit at gcc dot gnu.org 2022-10-14 10:47 ` [Bug tree-optimization/106513] [10 " cvs-commit at gcc dot gnu.org 2022-10-14 10:48 ` rguenth at gcc dot gnu.org
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