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From: "crazylht at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/98442] New: [X86] suboptimal for memset with CLEAR_BY_PIECES Date: Fri, 25 Dec 2020 01:38:35 +0000 [thread overview] Message-ID: <bug-98442-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98442 Bug ID: 98442 Summary: [X86] suboptimal for memset with CLEAR_BY_PIECES Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: crazylht at gmail dot com CC: hjl.tools at gmail dot com, wei3.xiao at intel dot com, wwwhhhyyy333 at gmail dot com Target Milestone: --- Target: x86_64-*-* i?86-*-* cat test.c -------- char Tab[64]; void foo(int n) { for (int i= 0; i != 64; i++) Tab[i] = 0; } ---- gcc generate ------ foo(int): vpxor xmm0, xmm0, xmm0 vmovdqa XMMWORD PTR Tab[rip], xmm0 vmovdqa XMMWORD PTR Tab[rip+16], xmm0 vmovdqa XMMWORD PTR Tab[rip+32], xmm0 vmovdqa XMMWORD PTR Tab[rip+48], xmm0 ret Tab: .zero 64 --------- Could be better ---- foo(int): vpxor ymm0, ymm0, ymm0 #4.5 vmovdqu YMMWORD PTR Tab[rip], ymm0 #4.5 vmovdqu YMMWORD PTR 32+Tab[rip], ymm0 #4.5 vzeroupper #6.1 ret #6.1 Tab: ----- GCC use 128-bit as default ---- bool default_use_by_pieces_infrastructure_p (unsigned HOST_WIDE_INT size, unsigned int alignment, enum by_pieces_operation op, bool speed_p) { unsigned int max_size = 0; unsigned int ratio = 0; switch (op) { case CLEAR_BY_PIECES: max_size = STORE_MAX_PIECES; ratio = CLEAR_RATIO (speed_p); ---- Define TARGET_USE_BY_PIECES_INFRASTRUCTURE_P for i386?
next reply other threads:[~2020-12-25 1:38 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-25 1:38 crazylht at gmail dot com [this message] 2020-12-31 3:38 ` [Bug target/98442] " crazylht at gmail dot com 2020-12-31 3:48 ` hjl.tools at gmail dot com 2020-12-31 3:56 ` hjl.tools at gmail dot com 2021-01-05 10:05 ` rguenth at gcc dot gnu.org 2021-10-06 23:48 ` hjl.tools at gmail dot com
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