-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I sure do wish the reply-to on mesa-commit message was automatically set to mesa-dev. :(
- -------- Original Message -------- Message-ID: <4c86e67c.2010...@freedesktop.org> Date: Tue, 07 Sep 2010 18:27:24 -0700 From: Ian Romanick <i...@freedesktop.org> User-Agent: Thunderbird 2.0.0.24 (X11/20100228) MIME-Version: 1.0 To: Luca Barbieri <l...@kemper.freedesktop.org> CC: mesa-com...@lists.freedesktop.org Subject: Re: Mesa (shader-work): glsl: introduce ir_binop_all_equal and ir_binop_any_equal, allow vector cmps References: <20100907233913.c73fc10...@kemper.freedesktop.org> In-Reply-To: <20100907233913.c73fc10...@kemper.freedesktop.org> X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Luca Barbieri wrote: > Module: Mesa > Branch: shader-work > Commit: 4b7392ae4856f7e602e8b5eda907497ab9953433 > URL: > http://cgit.freedesktop.org/mesa/mesa/commit/?id=4b7392ae4856f7e602e8b5eda907497ab9953433 > > Author: Luca Barbieri <l...@luca-barbieri.com> > Date: Wed Sep 8 01:31:39 2010 +0200 > > glsl: introduce ir_binop_all_equal and ir_binop_any_equal, allow vector cmps > > Currently GLSL IR forbids any vector comparisons, and defines "ir_binop_equal" > and "ir_binop_nequal" to compare all elements and give a single bool. > > This is highly unintuitive and prevents generation of optimal Mesa IR. > > Hence, first rename "ir_binop_equal" to "ir_binop_all_equal" and > "ir_binop_nequal" to "ir_binop_any_nequal". > > Second, readd "ir_binop_equal" and "ir_binop_nequal" with the same semantics > as less, lequal, etc. > > Third, allow all comparisons to acts on vectors. When I was doing the matrix comparison work, Eric and I had some discussions about this. Eric's suggestion, which I just never got around to implementing, was that all the equality comparisons be changed to (genType * genType) -> (boolGenType). Most of your patch implements this. With that in place, the GLSL equality operators would be translated as either: (expression bool any (expression boolGenType != (op0) (op1))) or (expression bool not (expression bool any (expression boolGenType != (op0) (op1)))) This seems better than having two different IR opcodes. I did some experiments with reimplementing all() using ir_unop_any (like in the IR above). This ended up generating worse final code in some places due to decreased constant folding. For example, the code: bvec4 a = bvec4(true, true, x > y, true); if (all(a)) { ... } gets translated to the following with the current implementation of all: if (true && true && (x > y) && true) { ... } This gets optimized to: if (x > y) { ... } Using ir_unop_any, we get stuck with: bvec4 a = bvec4(true, true, x > y, true); if (!any(not(a))) { ... } It never gets reduced because an expression is either completely constant or it's not constant at all. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkyG56wACgkQX1gOwKyEAw9xwgCfXhDrS6s6g1JAeWfm1LnM1lxE 8Q8Anjt8dWLCWyB+3xGrTlRbHDbaNmOm =hjBQ -----END PGP SIGNATURE----- _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
