similar to: Question on fast-math optimizations

Dear LLVM developers, I have a question on the fast-math floating-point optimizations applied by LLVM: Judging by the documentation at https://llvm.org/docs/LangRef.html#fast-math-flags I understood that rewriting with associativity and using reciprocal computations are possible optimizations. As the folklore description of fast-math is that it "applies real-valued identities", I

On 30.11.18 11:49, Heiko Becker via llvm-dev wrote: > --Resending my last mail, as it might have gotten lost -- > > Thanks Nicolai and Steve for the initial replies. > > So if I understand correctly there are 2 places you can pinpoint at > where distributivity is used: > > - simplification of infinity/NaN expressions > > - combination with FMA introduction Well

On Oct 13, 2014, at 3:44 PM, Chandler Carruth <chandlerc at google.com> wrote: > I actually have a particular allergy to member variable names and function names having similar styles: > > bool x = i->isMyConditionTrue; > > Did I mean to write 'isMyConditionTrue()'? Or 'bool &x = I->isMyConditionTrue'? Or something else? I have no idea. Warnings and

On Mon, Oct 13, 2014 at 4:25 PM, Xinliang David Li <xinliangli at gmail.com> wrote: > On Mon, Oct 13, 2014 at 4:00 PM, Chris Lattner <clattner at apple.com> wrote: > >> On Oct 13, 2014, at 3:44 PM, Chandler Carruth <chandlerc at google.com> >> wrote: >> > I actually have a particular allergy to member variable names and >> function names having

----- Original Message ----- > From: "Sanjay Patel" <spatel at rotateright.com> > To: "Hal J. Finkel" <hfinkel at anl.gov> > Cc: "Mehdi Amini" <mehdi.amini at apple.com>, "llvm-dev" > <llvm-dev at lists.llvm.org>, "cfe-dev" <cfe-dev at lists.llvm.org>, > "andrew kaylor" <andrew.kaylor at

On 22.08.2018 17:52, Ryan Taylor wrote: > This is probably going to effect on other backends and break llvm-lit > for them? Very likely, yes. Can you take a look at how big the fallout is? This might give us a hint about what other frontends might expect, and who needs to be involved in the discussion (if one is needed). Cheers, Nicolai > > On Wed, Aug 22, 2018 at 11:41 AM

Sent from my Verizon Wireless 4G LTE DROID On Nov 17, 2016 5:53 PM, Mehdi Amini <mehdi.amini at apple.com<mailto:mehdi.amini at apple.com>> wrote: > > >> On Nov 17, 2016, at 4:33 PM, Hal Finkel <hfinkel at anl.gov<mailto:hfinkel at anl.gov>> wrote: >> >> >> ________________________________ >>> >>> From: "Warren

This is just paraphrasing from D26602, so credit to Nicolai for first raising the issue there. float foo(float x, float y) { return x * (y + 1); } $ ./clang -O2 xy1.c -S -o - -target aarch64 -ffp-contract=fast | grep fm fmadd s0, s1, s0, s0 Is this a bug? We transformed the original expression into: x * y + x When x=INF and y=0, the code returns INF if we don't reassociate. With

On 22.08.2018 13:29, Ryan Taylor wrote: > The example starts as SPIR-V with the NoContraction decoration flag on > the fmul. > > I think what you are saying seems valid in that if the user had put the > flag on the fadd instead of the fmul it would not contract and so in > this example the user needs to put the NoContraction on the fadd though > I'm not sure

On 21.08.2018 16:08, Ryan Taylor via llvm-dev wrote: > So I have a test case where: > > %20 = fmul nnan arcp float %15, %19 > %21 = fadd reassoc nnan arcp contract float %20, -1.000000e+00 > > is being contracted in DAG to fmad. Is this correct since the fmul has > no reassoc or contract fast math flag? By having the reassoc and contract flags on fadd, the frontend is

I don't think the global fast math flag should override the NoContraction decoration as that's mostly the point of that decoration to begin with, to have fine granular control while still having a broad sweeping optimization. Did I miss your point? I feel like I did. On Thu, Aug 23, 2018, 3:42 PM Michael Berg <michael_c_berg at apple.com> wrote: > Ryan, > > Given that the

Maybe there is a cleaner solution but it seems like adding a 'nocontract' flag is close to the intention of spir-v and is an easy check in the DAGCombiner without breaking anything else and its intentions are very clear. Right now the DAGCombiner logic doesn't seem to be able to handle the case of having fast math globally with instruction level flags to turn off fast math. Right now,

Nicolai, Can you do without the use of -fp-contract=fast (Options.AllowFPOpFusion == FPOpFusion::Fast ) and without Unsafe? As I SPIR-V’s usage of NoContraction flies in the face of both. If so, you should be able to get what you want, as then you are down to just IR flags. You will need a model to generate the correct behavior though in your SPIR-V implementation wrt IR flag emissions.

On May 2, 2008, at 2:23 PM, me22 wrote: [...] > I suppose the most important issue is what constitutes "observable > behavior". 1.9/6: «The observable behavior of the abstract machine is its sequence of reads and writes to volatile data and calls to library I/O functions. [ Footnote 6: An implementation can offer additional library I/O functions as an extension.

Michael, >From the spec with regards to reassoc: – 15225 Include no re-association as a constraint required by the NoContraction Decoration. I don't see a solution given the situation where -fp-contract=fast and we want to contract. Furthermore, I think a 'nocontract' flag will allow the IR to be more readable in it's intention. The problem is you can have 2 fp arith

This looks like the right idea to me too. It may sound a bit weird to do that per instruction, but d3d11 does that as well. (Some d3d versions just have a global flag basically forbidding or allowing any such fast math optimizations in the assembly, but I'm not actually sure everybody honors that without tesselation...) For 1/9: Reviewed-by: Roland Scheidegger <sroland at vmware.com>

>All that said, I think we (the company I work for, Sony) will have to implement support >for these switches. It comes down to GCC has these switches (e.g., -fno-reciprocal-math >and -fno-associative-math), and they do suppress the transformations for our customers. >They switch to Clang/LLVM, they use the same switches, and it doesn't "work". So as a >practical

> If we are going to change how we name variables, I very much want them to > not collide with either type names or function names. My suggestion would be > "lower_case" names. > > This also happens to be the vastly most common pattern across all C++ coding > styles and C-based language coding styles I have seen. STL has "lower_case" functions, and exposes

On the plus side, I'm glad to see the conclusions of the last couple of posts. From Mehdi: > Hope this clarify where I see the direction going, and even if you don’t agree with my > reasoning, the conclusion should be satisfactory on your side :) I'd say that summarizes my thoughts on this well. And from Nicolai: > Right. I'm not fundamentally opposed to having these

> On Nov 17, 2016, at 1:44 PM, Mehdi Amini via llvm-dev <llvm-dev at lists.llvm.org> wrote: > >> >> On Nov 17, 2016, at 1:24 PM, Ristow, Warren <warren.ristow at sony.com> wrote: >> >> On the plus side, I'm glad to see the conclusions of the last couple of posts. >> >> From Mehdi: >> >>> Hope this clarify where I see the