similar to: NEON FP flags

Hi Renato, As I understand it, the fundamental property being addresses here is: Are the semantics of scalar FP math the same as vector FP math? TTI seems like a good place to expose that information. If the semantics are indeed different, then the vectorizer would require fast-math flags in order to vectorize FP operations (similarly, gcc's man page says it requires

On 25 March 2016 at 04:11, Hal Finkel <hfinkel at anl.gov> wrote: > As I understand it, the fundamental property being addresses here is: Are the semantics of scalar FP math the same as vector FP math? TTI seems like a good place to expose that information. If the semantics are indeed different, then the vectorizer would require fast-math flags in order to vectorize FP operations

On Fri, Mar 25, 2016 at 01:23:03PM +0000, Renato Golin via llvm-dev wrote: > On 25 March 2016 at 04:11, Hal Finkel <hfinkel at anl.gov> wrote: > > As I understand it, the fundamental property being addresses here is: Are > > the semantics of scalar FP math the same as vector FP math? TTI seems like > > a good place to expose that information. If the semantics are indeed

On 22 March 2016 at 11:34, James Molloy <James.Molloy at arm.com> wrote: > I don’t think this part is right. The denormal flag would have to be set by > whatever code generates the FP instruction, which would be Clang’s codegen > layer. So the if (Darwin) would be there, not in TTI. Right, I meant the information to set/not set would be in TTI, not the actual setting. I don't

On 06/07/2013 06:49 AM, Arnold Schwaighofer wrote: > > On Jun 7, 2013, at 3:14 AM, Renato Golin <renato.golin at linaro.org> wrote: > >> On 7 June 2013 08:48, Tobias Grosser <tobias at grosser.es> wrote: >> When to set which subtarget feature is a policy decision, where I honestly don't have any opinion on for clang. The best is probably to mirror the gcc

On 06/10/2013 01:56 AM, David Tweed wrote: > | For programs that have mixed precision requirements for floating point > | operations we probably need to do this according to the fast math flags. > | Until we get there, a good first step would probably be to provide a > | global option similar to -enable-no-infs-fp-math that specifies if > | denormals should be allowed or not. This

On Jun 7, 2013, at 3:14 AM, Renato Golin <renato.golin at linaro.org> wrote: > On 7 June 2013 08:48, Tobias Grosser <tobias at grosser.es> wrote: > When to set which subtarget feature is a policy decision, where I honestly don't have any opinion on for clang. The best is probably to mirror the gcc behavior on linux targets. > > Not really, since GCC has no special

Our processor also has some issues regarding the handling of denormals - scalar and vector - and we ran into a related problem only a few days ago. The v3.8 compiler has done a lot of good work on optimisations for floating-point math, but ironically one of them broke our implementation of 'nextafterf'. The desired code fragment (FP32) is: float xAbs = fabsf(x); since we know our

| For programs that have mixed precision requirements for floating point | operations we probably need to do this according to the fast math flags. | Until we get there, a good first step would probably be to provide a | global option similar to -enable-no-infs-fp-math that specifies if | denormals should be allowed or not. This would allow the user to specify | the precision requirements, without

Hi, > James, is that a correct assessment? Yes, it is also my belief that the only way ARMv7 NEON differs from IEEE754 is lack of denormal support. James > On 11 Feb 2016, at 10:53, Renato Golin <renato.golin at linaro.org> wrote: > > Hal, > > I had a read on the ARM ARM about VFP and SIMD FP semantics and my > analysis is that NEON's only problem is the

On 06/06/2013 11:58 PM, Renato Golin wrote: > On 7 June 2013 07:05, Owen Anderson <resistor at mac.com> wrote: Hi Owen, hi Renato, thanks for your replies. >> Darwin uses NEON for floating point, but does *not* (and should not). >> globally enable fast math flags. Use of NEON for FP needs to remain >> achievable without globally setting the fast math flags. Fast

Hi all, While reviewing a recent clang documentation change, I became aware of an issue with the way that clang is handling FP denormals. There is currently some support for variations in the way denormals are handled, but it isn't consistent across architectures and generally feels kind of half-baked. I'd like to discuss possible solutions to this problem. First, there is a clang

>> Darwin uses NEON for floating point, but does *not* (and should not). >> globally enable fast math flags. Use of NEON for FP needs to remain >> achievable without globally setting the fast math flags. Fast math may >> imply reasonably imply NEON, but the opposite direction is not accurate. | Good point. Fast math is probably a too tough requirement. I need to | look

On 7 June 2013 14:49, Arnold Schwaighofer <aschwaighofer at apple.com> wrote: > It is not the vectorizer that is the issue, it is the ARM backend that > currently translates vectorized floating point IR to NEON instructions (it > should scalarize it if desired to do so - i.e. if people care about > denormals). > Hi Arnold, Can't the vectorizer not generate the v4f32

> |I just looked again at the +neonfp flag. Compiling with and without > |+neonfp flag seems to only affect scalar types in the attached test > |case. If e.g. the LLVM vectorizer introduces vector instructions on > |LLVM-IR level floating point vectors still yield NEON assembly even if > |compiled with "-mattr=+neon,-neonfp". Is this expected? > > I'm virtually

On Mon, Sep 16, 2019 at 9:43 PM Matt Arsenault via cfe-dev < cfe-dev at lists.llvm.org> wrote: > > > On Sep 16, 2019, at 19:57, Kaylor, Andrew via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > > > Do we need an ftz fast-math flag? > > > This would be useful for matching a handful of AMDGPU instructions (a fmad > that only always flushes being the

We knew the day when we needed another FMF bit was coming back in: https://reviews.llvm.org/D39304 ...it was just a question of 'when'. :) I'm guessing that an FTZ bit won't be the last new bit needed if we consider permutations between strict FP and fast-math. Even without that, denormals-as-zero (DAZ) might also be useful? So rather than continuing to carve these out bit-by-bit,

Hi, | The question is: | * is this a problem with the test, that shouldn't be expecting values below FLT_MIN, or | * is it a bug in the lowering, that should only be lowering to NEON's VMUL when unsafe-math is on, or | * neither, and people should disable that when they want correctness? Note that if you go for the second option, IMO unsafe-math is _far_ too "aggressive" an

Renato, I think we agree. On Jun 7, 2013, at 11:53 AM, Renato Golin <renato.golin at linaro.org> wrote: > On 7 June 2013 15:41, Arnold Schwaighofer <aschwaighofer at apple.com> wrote: > We don’t want to encode backend knowledge into the vectorizer (i.e. don’t vectorize type X because the backend does not support it). > > We already do, via the cost table. This case is no

On Jun 7, 2013, at 9:22 AM, Renato Golin <renato.golin at linaro.org> wrote: > On 7 June 2013 14:49, Arnold Schwaighofer <aschwaighofer at apple.com> wrote: > It is not the vectorizer that is the issue, it is the ARM backend that currently translates vectorized floating point IR to NEON instructions (it should scalarize it if desired to do so - i.e. if people care about