From: Linus Torvalds <torvalds@linux-foundation.org>
To: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Sparse Mailing-list <linux-sparse@vger.kernel.org>,
Christopher Li <sparse@chrisli.org>
Subject: Re: [PATCH v5 04/14] rewrite compare_opcode() like swap_compare_opcode()
Date: Fri, 24 Mar 2017 16:24:39 -0700 [thread overview]
Message-ID: <CA+55aFzgt9iAKQqNzBPDFT=kTL9sP=OyjsQOJ+mxuJYQRwPQkg@mail.gmail.com> (raw)
In-Reply-To: <20170324231421.14869-5-luc.vanoostenryck@gmail.com>
On Fri, Mar 24, 2017 at 4:14 PM, Luc Van Oostenryck
<luc.vanoostenryck@gmail.com> wrote:
> More precisely, use a table to get the opcdoe corresponding
> to the negated compare and use a more explicit name for the
> function.
Side note: this code should verify that it doesn't operate on a
floating point compare.
You can't negate a FP compare, because the negation doesn't
necessarily have the opposite value.
For example, "a < b" is *not* the same as "!(a >= b)" for floating
point values when one of them is a NaN. Both < and >= will compare as
false, so "negating" the op won't actually negate the resulting
logical operation.
Linus
next prev parent reply other threads:[~2017-03-24 23:24 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-24 23:14 [PATCH 00/14] prepare LLVM fixes Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 01/14] don't output value of anonymous symbol's pointer Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 02/14] canonicalize binops before simplification Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 03/14] canonicalize compare instructions Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 04/14] rewrite compare_opcode() like swap_compare_opcode() Luc Van Oostenryck
2017-03-24 23:24 ` Linus Torvalds [this message]
2017-03-24 23:54 ` Luc Van Oostenryck
2017-03-25 23:35 ` Christopher Li
2017-03-26 0:22 ` Luc Van Oostenryck
2017-03-27 16:29 ` Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 05/14] add is_signed_type() Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 06/14] fix usage of inlined calls Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 07/14] inlined calls should not block BB packing Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 08/14] give function's arguments a type via OP_PUSH Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 09/14] insure that all OP_PUSHs are just before their OP_CALL Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 10/14] give a type to OP_PHISOURCEs Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 11/14] give a type to OP_SELs, always Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 12/14] give a type to OP_SWITCHs Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 13/14] add doc about sparse's instructions/IR Luc Van Oostenryck
2017-03-24 23:14 ` [PATCH v5 14/14] add support for wider type in switch-case Luc Van Oostenryck
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