search for: fmuladd

A little background: The fmuladd intrinsic was introduced to support the FP_CONTRACT pragma in C. llvm.fmuladd.* is generated by clang when it sees an expression of the form 'a * b + c' within a single source statement. If you want to opportunistically form FMA target instructions my inclination would be to skip llvm.fmu...

Hi, I would like to add an ISD node for an fmad operation (named either FMAD or FMULADD). It will have the semantics of returning the same result as the separate multiply and add with the intermediate rounding step, and not a differently rounded result. The motivation is to share code with the various FMA forming DAG combines, but will be generally more useful on targets that sup...

Thanks for all the replies - it pretty much confirmed what I think I'd worked out about how fmuladd is supposed to behave. But my initial query wasn't asking what fmuladd did - it was asking for the documentation about it to be clarified. Can I suggest that the Overview section for fmuladd is changed to say the following (the key point being the removal of the word "legal" in the d...

The fmuladd intrinsic is described as saying that a multiply and addition sequence can be fused into an fma instruction "if the code generator determines that the fused expression would be legal and efficient". (http://llvm.org/docs/LangRef.html#llvm-fma-intrinsic) I've spent a bit of time puzzl...

Hal Finkel <hfinkel at anl.gov> writes: > There are a few conditions that contribute to the decision of whether > or not to make the fmuladd -> fma translation. The relevant code is in > CodeGen/SelectionDAG/SelectionDAGBuilder.cpp: > > case Intrinsic::fmuladd: { > EVT VT = TLI.getValueType(I.getType()); > if (TM.Options.AllowFPOpFusion != FPOpFusion::Strict && > TLI.isOperationLegal(ISD::F...

...gmail.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "David A. Greene" <dag at cray.com>, "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Friday, January 11, 2013 2:19:01 PM > Subject: Re: [LLVMdev] Documentation of fmuladd intrinsic > > > On Fri, Jan 11, 2013 at 3:16 PM, Hal Finkel < hfinkel at anl.gov > > wrote: > > > > > > ----- Original Message ----- > > From: dag at cray.com > > To: "Justin Holewinski" < justin.holewinski at gmail.com > > &...

Hi, Eli, Mike and Lang: Thank you all for the input. This is one e.g which might be difficult for isel: a*b + c*d + e => a*b + (c*d + e). Thanks Shuxin On 12/12/12 4:43 PM, Lang Hames wrote: > A little background: > > The fmuladd intrinsic was introduced to support the FP_CONTRACT pragma > in C. llvm.fmuladd.* is generated by clang when it sees an expression > of the form 'a * b + c' within a single source statement. > > If you want to opportunistically form FMA target instructions my > inclinatio...

...olewinski" <justin.holewinski at gmail.com> > > Cc: "Hal Finkel" <hfinkel at anl.gov>, "LLVM Developers Mailing List" < > llvmdev at cs.uiuc.edu> > > Sent: Friday, January 11, 2013 2:13:50 PM > > Subject: Re: [LLVMdev] Documentation of fmuladd intrinsic > > > > Justin Holewinski <justin.holewinski at gmail.com> writes: > > > > > Out of curiosity, what is the use-case for > > > isFMAFasterThanMulAndAdd? > > > If a target declares that FMA is actually slower for a given type, > > &g...

----- Original Message ----- > From: "Cameron McInally" <cameron.mcinally at nyu.edu> > To: "Andrew Booker" <andrew.booker at arm.com> > Cc: llvmdev at cs.uiuc.edu > Sent: Friday, January 11, 2013 12:37:07 PM > Subject: Re: [LLVMdev] Documentation of fmuladd intrinsic > > > On Fri, Jan 11, 2013 at 1:08 PM, Andrew Booker < > andrew.booker at arm.com > wrote: > > > > The fmuladd intrinsic is described as saying that a multiply and > addition sequence can be fused into an fma instruction "if the code > generat...

...t; To: "Justin Holewinski" <justin.holewinski at gmail.com> > Cc: "Hal Finkel" <hfinkel at anl.gov>, "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Friday, January 11, 2013 2:13:50 PM > Subject: Re: [LLVMdev] Documentation of fmuladd intrinsic > > Justin Holewinski <justin.holewinski at gmail.com> writes: > > > Out of curiosity, what is the use-case for > > isFMAFasterThanMulAndAdd? > >  If a target declares that FMA is actually slower for a given type, > > why not just declare it as ill...

...look at in-tree target implementations as an example. Please let me know if there are any objections before tomorrow morning. Stephen ---------- Forwarded message ---------- From: Stephen Lin <swlin at post.harvard.edu> Date: Sun, Jul 7, 2013 at 9:25 PM Subject: [PATCH] Resolve issues with fmuladd intrinsic handling across multiple backends To: llvm-commits at cs.uiuc.edu Hi, While working on another patch, I discovered multiple related issues with fmuladd intrinsic handling which I believe the attached patch resolves. Currently, the operation depends on the target's implementation o...

...39;m going implement FMA formation. On some architectures, "FMA a, b, c" is more precise than > "a * b + c". I'm wondering if FMA could be less precise. In the former case, can we enable FMA > formation despite restrictive FP mode? > I believe that a pass to form fmuladd[1] intrinsic calls would be very useful! The fmuladd intrinsic is defined such that its formation should be isolated from worries about strictness. It simply means "a * b + c" and leaves the decision of whether or not to fuse up to the code generator. Of course, one probably would only ru...

On Fri, Jan 11, 2013 at 1:08 PM, Andrew Booker <andrew.booker at arm.com>wrote: > The fmuladd intrinsic is described as saying that a multiply and > addition sequence can be fused into an fma instruction "if the code > generator determines that the fused expression would be legal and > efficient". (http://llvm.org/docs/LangRef.html#llvm-fma-intrinsic) > > I've s...

We have a function that has 256 loads and 256 fmuladds. This block of operations is bounded at either end by an OpenCL barrier (an AMDIL fence instruction). The loads and multiply/adds are ordinarily interleaved... that is, the IR going in to code generation looks like: %39 = load float addrspace(3)* getelementptr inbounds ([16 x [17 x float]] addrs...

Hi, Dear All: I'm going implement FMA formation. On some architectures, "FMA a, b, c" is more precise than "a * b + c". I'm wondering if FMA could be less precise. In the former case, can we enable FMA formation despite restrictive FP mode? Thanks Shuxin

...ateright.com>> wrote: > > If I have my FMA intrinsics story straight now (thanks for the explanation, Hal!), I think it raises another question about IR canonicalization (and may affect the proposed revision to IR FMF): No, I think that we specifically don't want to canonicalize to fmuladd at the IR level at all. If the backend has the freedom to form FMAs as it sees fit, then we should delay the decision until whenever the backend finds most appropriate. Some backends, for example, form FMAs using the MachineCombiner pass which considers critical path, latency, throughputs, etc. in...

...----- > > From: "Cameron McInally" <cameron.mcinally at nyu.edu> > > To: "Andrew Booker" <andrew.booker at arm.com> > > Cc: llvmdev at cs.uiuc.edu > > Sent: Friday, January 11, 2013 12:37:07 PM > > Subject: Re: [LLVMdev] Documentation of fmuladd intrinsic > > > > > > On Fri, Jan 11, 2013 at 1:08 PM, Andrew Booker < > > andrew.booker at arm.com > wrote: > > > > > > > > The fmuladd intrinsic is described as saying that a multiply and > > addition sequence can be fused into an fma in...

...ry straight now (thanks for the > > > explanation, Hal!), I think it raises another question about IR > > > canonicalization (and may affect the proposed revision to IR FMF): > > > > > > No, I think that we specifically don't want to canonicalize to > > fmuladd at the IR level at all. If the backend has the freedom to > > form FMAs as it sees fit, then we should delay the decision until > > whenever the backend finds most appropriate. Some backends, for > > example, form FMAs using the MachineCombiner pass which considers > > criti...

Justin Holewinski <justin.holewinski at gmail.com> writes: > Out of curiosity, what is the use-case for isFMAFasterThanMulAndAdd? >  If a target declares that FMA is actually slower for a given type, > why not just declare it as illegal for that type?  Wouldn't that > accomplish the same thing without another target hook?  I feel like I'm > missing something here.

...d (fadd (fmul a b) (fmul c d)) e) How would your pass go about handling these patterns and is that something that would be too complicated for fast-isel to do on the fly? > Thanks > Shuxin > > On 12/12/12 4:43 PM, Lang Hames wrote: >> A little background: >> >> The fmuladd intrinsic was introduced to support the FP_CONTRACT pragma in C. llvm.fmuladd.* is generated by clang when it sees an expression of the form 'a * b + c' within a single source statement. >> >> If you want to opportunistically form FMA target instructions my inclination would b...