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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/98865] Missed transform of (a >> 63) * b Date: Thu, 19 May 2022 16:55:48 +0000 [thread overview] Message-ID: <bug-98865-4-mcUulvlqy5@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-98865-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98865 --- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>: https://gcc.gnu.org/g:d863ba23fb16122bb0547b0c678173be0d98f43c commit r13-673-gd863ba23fb16122bb0547b0c678173be0d98f43c Author: Roger Sayle <roger@nextmovesoftware.com> Date: Thu May 19 17:54:38 2022 +0100 PR middle-end/98865: Expand X*Y as X&-Y when Y is [0,1]. The patch is a revised solution for PR middle-end/98865 incorporating the feedback/suggestions from Richard Biener's review here: https://gcc.gnu.org/pipermail/gcc-patches/2022-May/593928.html Most significantly, this patch now performs the transformation/optimization during RTL expansion, where the target's rtx_costs can be used to determine whether the original multiplication (that may potentially be implemented by a shift or lea) is cheaper than a negation and a bit-wise and. Previously the expression (x>>63)*y would be compiled with -O2 as shrq $63, %rdi movq %rdi, %rax imulq %rsi, %rax but with this patch now produces: sarq $63, %rdi movq %rdi, %rax andq %rsi, %rax Likewise the expression (x>>63)*135 [that appears in a hot-spot of the Botan AES-128 benchmark] was previously: shrq $63, %rdi leaq (%rdi,%rdi,8), %rdx movq %rdx, %rax salq $4, %rax subq %rdx, %rax now becomes: movq %rdi, %rax sarq $63, %rax andl $135, %eax 2022-05-19 Roger Sayle <roger@nextmovesoftware.com> gcc/ChangeLog PR middle-end/98865 * expr.cc (expand_expr_real_2) [MULT_EXPR]: Expand X*Y as X&Y when both X and Y are [0, 1], X*Y as X&-Y when Y is [0,1] and likewise X*Y as -X&Y when X is [0,1] using tree_nonzero_bits. gcc/testsuite/ChangeLog PR middle-end/98865 * gcc.target/i386/pr98865.c: New test case.
next prev parent reply other threads:[~2022-05-19 16:55 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-01-28 13:38 [Bug middle-end/98865] New: " rguenth at gcc dot gnu.org 2021-01-28 13:40 ` [Bug middle-end/98865] " rguenth at gcc dot gnu.org 2021-01-28 14:26 ` jakub at gcc dot gnu.org 2021-03-07 2:46 ` pinskia at gcc dot gnu.org 2021-07-20 22:19 ` pinskia at gcc dot gnu.org 2021-09-22 18:19 ` cvs-commit at gcc dot gnu.org 2022-01-11 11:19 ` rguenth at gcc dot gnu.org 2022-05-18 15:24 ` cvs-commit at gcc dot gnu.org 2022-05-19 16:55 ` cvs-commit at gcc dot gnu.org [this message] 2022-05-27 8:02 ` cvs-commit at gcc dot gnu.org 2022-05-28 9:18 ` roger at nextmovesoftware dot com
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