From 904fb64d2b643d940d6326485a5a187747c2367e Mon Sep 17 00:00:00 2001 From: Staf Verhaegen Date: Sat, 16 May 2020 13:30:51 +0200 Subject: [PATCH] Re: [libre-riscv-dev] Introduction and Questions --- 6e/3fc364c1ea82d8e6c801b31f651788c17296a7 | 146 ++++++++++++++++++++++ 1 file changed, 146 insertions(+) create mode 100644 6e/3fc364c1ea82d8e6c801b31f651788c17296a7 diff --git a/6e/3fc364c1ea82d8e6c801b31f651788c17296a7 b/6e/3fc364c1ea82d8e6c801b31f651788c17296a7 new file mode 100644 index 0000000..765dae7 --- /dev/null +++ b/6e/3fc364c1ea82d8e6c801b31f651788c17296a7 @@ -0,0 +1,146 @@ +Return-path: +Envelope-to: publicinbox@libre-riscv.org +Delivery-date: Sat, 16 May 2020 12:31:04 +0100 +Received: from localhost ([::1] helo=libre-riscv.org) + by libre-soc.org with esmtp (Exim 4.89) + (envelope-from ) + id 1jZv1y-0006WY-PG; Sat, 16 May 2020 12:31:02 +0100 +Received: from vps2.stafverhaegen.be ([85.10.201.15]) + by libre-soc.org with esmtp (Exim 4.89) + (envelope-from ) id 1jZv1w-0006WO-Hn + for libre-riscv-dev@lists.libre-riscv.org; Sat, 16 May 2020 12:31:00 +0100 +Received: from localhost.localdomain (hpdc7800 [10.0.0.1]) + by vps2.stafverhaegen.be (Postfix) with ESMTP id BEF9311C0543 + for ; + Sat, 16 May 2020 13:30:59 +0200 (CEST) +To: libre-riscv-dev@lists.libre-riscv.org +References: + <747F8870-06C6-46A0-AFD9-D55289D4C41A@gatech.edu> + + <4BDA96A5-9063-42A6-9548-CAE3CBEBEBAC@gatech.edu> + + + + + + + +From: Staf Verhaegen +Autocrypt: addr=staf@fibraservi.eu; prefer-encrypt=mutual; keydata= + xsBNBFrIskcBCADcmvPcGj3WfInZqMlMeLn6COYJnO6bFcDmu0H/7eQ6LDhd5171d+3WSdNN + DD6TFgFNWu2qWf7CO9bkp8lmEZ2+T+5detfu/SdddL0lkK2GlIHXah7TnY9Lpr4YykDFL2kX + fbdMs32pOnvcK7Jhg/zKBzQyN3wHBPvpBqBnaWfMOMMvigTOAL3/jLPX1+TZ4JiA0YFsJwY5 + 7ytoqMXUi15eMGCW2URQ+iI35dSCqhyAy375DPjl9Q2veo4g10BruP6C7Qp2Qti3ytQEc1lJ + NBMQPdWpxp7kugyoun0U/MYUypc6Todt5SIA47Igo6Mw/x7j5bifepY7Fg8YpUcQV2hHABEB + AAHNI1N0YWYgVmVyaGFlZ2VuIDxzdGFmQGZpYnJhc2VydmkuZXU+wsB5BBMBAgAjBQJayLJH + AhsDBwsJCAcDAgEGFQgCCQoLBBYCAwECHgECF4AACgkQR9EEKdzPltxQaAf+IZBuNgJVeFsQ + YNH6iYB23khq27NnFBiRs6gQd6UqSvWESHg3soafuDqYm5aNFTgHkZBzaE+/qP5qOX2Dhj28 + 9vSwkvHqlhW6ZQP9hnz3XOK+/IT1fdT8GwJAR4JSJn01nroZZf7QWqY/MO42zu9+pRy8ddQo + c8AN8WOyowM1apDuu7rLibaWpuBFEEsYkOewjDVFksUcBrsPdNw1I+bw5QifP9/S8xE2W4/c + 3BnUROc6TPvJnY7sIREmccdhBOUXNTk1pNXaEnMEBkiVEURgWM+ikonG/dRCNmZM+oclhB4L + f2kS4JMEA/lSLVG9tguL2hMp9dPkdO1QPVM0L5972M7ATQRayLJHAQgAvpQaZJ5FZdqONoOI + p2iH3AUX+LLEMQRIu6ms4yq/yC4DCnOA2BIqq9FcgNUMGY7EJjPYkkqoz7/Yc4OqSrlpqWYC + fdPOMgDTlUTxUd+uWwvmSflEQHqGIN3r3IkXB4OiNDT7+VxZHxUepLU+CzbwpAUT24gH/P5q + yCEomTXSovOwW9tLXXhqdTsq8Wv+MrjNAZgDWXTUt6QQh779xnrpIb0foa2av7hlWvxTeRzu + RsIMP3pnm8Y8UDLkw/G3SPVC5bnRIcbrbTOOc79xjivKaF4/VkQGgd4IPZlNKX4YoMtldVIe + UyCo/RE9oZMHpvsMhH4VFlE3wZ6AR27qxpb5dwARAQABwsBfBBgBAgAJBQJayLJHAhsMAAoJ + EEfRBCncz5bcNWAIAKFCWJE6RqUjdshPGy/GLUBfr3dk3M1jjmyvM9SwV9Am7cTyoeJmMG0I + rGJINH7HVQqpfeb7SOiQIrBDC0MVyuP6aYnOD2FACSf1plK6bj2CdJAbJupBOC5Fp3p2+Jkz + 0ojwQWJul3FTpDqpgat3UX/FySr6em+Jxnfn4dPJ+5wudTQLNdDUw2GHXIKewFnJxZFGVKrV + LeGoZ1J9Tcckw7R2BtUrZNgIExxzLD7G+wE48uBP1WVpOWYMcyHslXlA9sSCGSAOPNGaecwL + nAZvnFlCbNmNrVMiwGgVydeH+oXIkXzjzov8NZtbxJzjgyCi9gIcKj730jtgAjRCKfScI64= +Message-ID: <7c84f530-fc12-0f4e-8a1c-7e58a1b498c3@fibraservi.eu> +Date: Sat, 16 May 2020 13:30:51 +0200 +User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 + Thunderbird/68.7.0 +MIME-Version: 1.0 +In-Reply-To: +X-Content-Filtered-By: Mailman/MimeDel 2.1.23 +Subject: Re: [libre-riscv-dev] Introduction and Questions +X-BeenThere: libre-riscv-dev@lists.libre-riscv.org +X-Mailman-Version: 2.1.23 +Precedence: list +List-Id: Libre-RISCV General Development + +List-Unsubscribe: , + +List-Archive: +List-Post: +List-Help: +List-Subscribe: , + +Reply-To: Libre-RISCV General Development + +Content-Type: multipart/mixed; boundary="===============8438699356721995198==" +Errors-To: libre-riscv-dev-bounces@lists.libre-riscv.org +Sender: "libre-riscv-dev" + +This is an OpenPGP/MIME signed message (RFC 4880 and 3156) +--===============8438699356721995198== +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="14KFMkcVJ7dQDl7UpCgxT0L7T9Verovsv" + +This is an OpenPGP/MIME signed message (RFC 4880 and 3156) +--14KFMkcVJ7dQDl7UpCgxT0L7T9Verovsv +Content-Type: multipart/mixed; boundary="NyNGFtqQ9YKwV65VvuYvJnNWW9hlClfKH" + +--NyNGFtqQ9YKwV65VvuYvJnNWW9hlClfKH +Content-Type: text/plain; charset=utf-8 +Content-Transfer-Encoding: quoted-printable +Content-Language: en-US + + +Op 16/05/2020 om 11:47 schreef Staf Verhaegen: +> Jeremy Singher schreef op vr 15-05-2020 om 16:49 [-0700]: +>> +>> Hmmm, ignoring WAW will significantly limit the ability of the core to= + +>> exploit ILP, which is one of the fundamental reasons for going OOO. +> I've wondered about this myself. Can you give concrete example of where= + +> not supporting a WAW hazard blocks ILP ? +> I am asking because just a WAW hazard could be easily avoided by a good= + +> peep hole optimizer in software because it would see that the output of= + +> the first write is never used. + +Ok after some reflection I do see the most possible performance +difference in procedures calls. Most of the time in procedures some +scratch registers are pushed on the stack at entering. + +Assume a write to a scratch register is still pending when doing a +procedure. With real register renaming the register stack push does not +need to block until write to register is complete, if it doesn't the +register push will block. + +The question is special hardware provision need to be done to optimize +this case or if one would rely on proper inlining of functions by the +compiler for performance critical code. Personally I don't see a problem +with relying on the latter. + +greets, +Staf. + + + +--NyNGFtqQ9YKwV65VvuYvJnNWW9hlClfKH-- + +--14KFMkcVJ7dQDl7UpCgxT0L7T9Verovsv-- + + +--===============8438699356721995198== +Content-Type: text/plain; charset="utf-8" +MIME-Version: 1.0 +Content-Transfer-Encoding: base64 +Content-Disposition: inline + +X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KbGlicmUtcmlz +Y3YtZGV2IG1haWxpbmcgbGlzdApsaWJyZS1yaXNjdi1kZXZAbGlzdHMubGlicmUtcmlzY3Yub3Jn +Cmh0dHA6Ly9saXN0cy5saWJyZS1yaXNjdi5vcmcvbWFpbG1hbi9saXN0aW5mby9saWJyZS1yaXNj +di1kZXYK + +--===============8438699356721995198==-- + + -- 2.30.2