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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/107972] backward propagation of finite property not performed Date: Tue, 06 Dec 2022 09:57:45 +0000 [thread overview] Message-ID: <bug-107972-4-uhUHPhOAw0@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-107972-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107972 Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |amacleod at redhat dot com --- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- The backwards propagation fixed, but neither: double foo (double a, double b) { if (!__builtin_isfinite (a)) return 42.0; if (!__builtin_isfinite (b)) return 42.0; double res = a + b; if (!__builtin_isfinite (res)) __builtin_unreachable (); return res; } double bar (double a, double b) { if (!__builtin_isfinite (a)) return 42.0; if (!__builtin_isfinite (b)) return 42.0; double res = a - b; if (!__builtin_isfinite (res)) __builtin_unreachable (); return res; } double baz (double a, double b) { if (!__builtin_isfinite (a)) return 42.0; if (!__builtin_isfinite (b)) return 42.0; double res = a * b; if (!__builtin_isfinite (res)) __builtin_unreachable (); return res; } double qux (double a, double b) { if (!__builtin_isfinite (a)) return 42.0; double res = a / b; if (!__builtin_isfinite (res)) __builtin_unreachable (); return res; } double quux (double a, double b) { if (!__builtin_isfinite (b)) return 42.0; double res = a / b; if (__builtin_isnan (res) || res == 0.0) __builtin_unreachable (); return res; } nor double foo (double a, double b) { if (!__builtin_isfinite (a)) return 42.0; if (!__builtin_isfinite (b)) return 42.0; double res = a + b; __attribute__((assume (__builtin_isfinite (res)))); return res; } double bar (double a, double b) { if (!__builtin_isfinite (a)) return 42.0; if (!__builtin_isfinite (b)) return 42.0; double res = a - b; __attribute__((assume (__builtin_isfinite (res)))); return res; } double baz (double a, double b) { if (!__builtin_isfinite (a)) return 42.0; if (!__builtin_isfinite (b)) return 42.0; double res = a * b; __attribute__((assume (__builtin_isfinite (res)))); return res; } double qux (double a, double b) { if (!__builtin_isfinite (a)) return 42.0; double res = a / b; __attribute__((assume (__builtin_isfinite (res)))); return res; } double quux (double a, double b) { if (!__builtin_isfinite (b)) return 42.0; double res = a / b; __attribute__((assume (!__builtin_isnan (res) && res != 0.0))); return res; } avoids the 4.2e+1 cases in the output, because in neither case we properly determine the ranges of res (that it is in foo/bar/baz/qux [-DBL_MAX,DBL_MAX]). For quux I think we don't have a way to represent that right now, we'd need a union of 2 ranges and after all, we also flush denormals to zero, so I think we'd need if (!(res < 1.0)) __builtin_unreachable (); or __attribute__((assume (res < 1.0))); so that we get [1.0, +INF] non-NAN range. Aldy/Andrew, any ideas what's going on?
next prev parent reply other threads:[~2022-12-06 9:57 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-12-05 13:35 [Bug tree-optimization/107972] New: " drepper.fsp+rhbz at gmail dot com 2022-12-05 13:43 ` [Bug tree-optimization/107972] " jakub at gcc dot gnu.org 2022-12-06 9:27 ` cvs-commit at gcc dot gnu.org 2022-12-06 9:57 ` jakub at gcc dot gnu.org [this message] 2022-12-07 15:31 ` amacleod at redhat dot com 2023-02-14 21:28 ` amacleod at redhat dot com
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