similar to: fenv.h vs the optimizer

I've recently been looking at how to implement in LLVM IR the rounding of floating point values when casting using different rounding modes and I've hit some problems. It seems that when casting down floats to less precise types the ``fptrunc`` LLVM IR instruction is used. The LLVM language reference suggests that it just truncates the value (which would be equivalent to rounding towards

Copying the list on a discussion of potentially general interest.... From: Kaylor, Andrew Sent: Friday, November 03, 2017 1:11 PM To: 'Ding, Wei' <Wei.Ding2 at amd.com>; Sumner, Brian <Brian.Sumner at amd.com>; Arsenault, Matthew <Matthew.Arsenault at amd.com> Subject: RE: clarification needed for the constrained fp implementation. Hi Wei, I've been meaning to

On 11/03/2017 05:26 PM, 陳韋任 via llvm-dev wrote: > > > 2017-11-04 4:29 GMT+08:00 Kaylor, Andrew via llvm-dev > <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>>: > > Copying the list on a discussion of potentially general interest…. > > *From:* Kaylor, Andrew > *Sent:* Friday, November 03, 2017 1:11 PM > *To:* 'Ding,

> > I'm not sure why this is an issue. Yes, these two intrinsics depend > on the current rounding mode according to the C standard, and yes, > LLVM in default mode assumes that the current rounding mode is the > default rounding mode. But the same holds true for many other > intrinsics and even the arithmetic IR operations like add. Any other intrinsic, like `floor`,

Hi all, A question came up in a code review (https://reviews.llvm.org/D72820) about whether or not to allow fast-math flags to be applied to constrained floating point intrinsics (http://llvm.org/docs/LangRef.html#constrained-floating-point-intrinsics). This has come up several times before, but I don't think we've ever made a decision about it. By default, the optimizer assumes that

We really have been trying to keep in mind that LLVM needs to support multiple front ends, which may be implementing different language standards. As much as possible, I’ve been trying to let the IEEE 754 spec drive my thinking about this, though I’ll admit that on a few points I’ve use the C99 spec as a sort of reference interpretation of IEEE 754. LLVM’s IRBuilder has been recently updated to

Some clarification after getting feedback from Craig Topper…. It’s probably best to say in the documentation that the llvm.nearbyint and llvm.rint functions “assume the default rounding mode, roundToNearest”. This will allow the optimizer to transform them as if they were rounding to nearest without requiring backends to use an encoding that enforces roundToNearest as the rounding mode for these

> > The only issue I see is that since we also assume FP operations have no > side effects by default there is no difference between llvm.rint and > llvm.nearbyint. I wouldn’t have a problem with dropping llvm.rint > completely. The forthcoming C standard ( http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2454.pdf, 7.12.9.8) defines new function, `roundeven`, which implements

Changing the list from cfe-dev to llvm-dev > On 20 Apr 2017, at 4:52 AM, Michael Clark <michaeljclark at mac.com> wrote: > > I’m getting close. I think it may be an issue with an individual intrinsic. I’m looking for the X86 lowering of Instruction::FPToUI. > > I found a comment around the rationale for using a conditional move versus a branch. I believe the predicate logic

> > One concern with replacing llvm.rint and llvm.nearbyint with > llvm.roundeven makes it difficult to turn back into a libcall if the > backend doesn't have an instruction for it. You can't just call the > roundeven library function since that wouldn't exist in older libm > implementations. So ideally you would know which function was originally > used in the

Let me clarify. These aren’t intended to be exposed to the user. The user code that leads to the generation of these intrinsics will be normal floating point operations combined with either pragmas (such as “STDC FENV_ACCESS ON”) or command line options (such as the recently introduced “-fp-model=strict”). The reason I’ve been avoiding normal constant values is that it provides no information when

Thanks, Andy. I'm not sure how to solve that or my case given the DAG's basic-block limit. Probably CodeGenPrepare or SelectionDAGBuilder...or we wait until after isel and try to split it up in a machine instruction pass. I filed my example here: https://bugs.llvm.org/show_bug.cgi?id=33013 Feel free to comment there and/or open a new bug for the FP_TO_UINT case. On Thu, May 11, 2017 at

On 10/03, Kaylor, Andrew via llvm-dev wrote: > I’d like to emphasize that the constrained intrinsics prevent > optimizations *by default*. We have a plan to go back and teach > individual optimizations how to handle these intrinsics. The idea is > that if an optimization knows nothing about the constrained intrinsics > then it won’t try to transform them, but if an optimization has

On Tue, 18 Apr 2006 23:27:39 -0700 Evan Cheng <evan.cheng at apple.com> wrote: > Hi Simon, > > The x86 backend does generate scalar SSE2 instructions. For your > example, it should emit something like: Oh, how did you get this ? [...] > > There is nothing here that should cause an exception. Are you using a > release or cvs? CVS. >From what I remember,

On Wed, 19 Apr 2006 19:28:34 +0100 Simon Burton <simon at arrowtheory.com> wrote: > > >From what I remember, this is a bug in debian libc: > some floating point flags are set incorrectly causing SIGFPE. > Can't find the bug report ATM. Oh, it just showed up on numpy-discussion: http://sources.redhat.com/bugzilla/show_bug.cgi?id=10 """ #include

> This seems like it was done for perf reason (mispredict). Conditional-to-cmov transformation should keep > from introducing additional observable side-effects, and it's clear that whatever did this did not account > for floating point exception. That’s a very reasonable statement, but I’m not sure it corresponds to the way we have typically approached this sort of problem. In

Hi All, I am trying to build the 'lld' linker on Mac OS 10.9, but during the build, I am getting the errors. Following are the steps that I have followed: 1.     I have downloaded the ‘llvm-stable’ source code from the following location:   https://github.com/llvm-mirror/llvm/tree/stable   2.     Machine details(on which llvm source code isbeing built) are as follows: $ sw_vers

This file is for configure+make build, not CMake, so I'm not sure why it's being included into your build (these failures aren't reproducible for me). Can you please list the exact steps you're doing to build LLVM with CMake and make sure you don't have additional CFLAGS (LDFLAGS etc) defined? On Mon, Nov 11, 2013 at 6:16 PM, Jack Howarth <howarth at bromo.med.uc.edu>

Hallo all, I was trying to Build LLVM with the cmake option LLVM_ENABLE_MODULES just out of curiosity. I used the RELEASE_400/final tag. It didn't work as I almost expected. So I'm wondering if the modulemaps aren't maintained anymore? If they aren't maintained anymore, why aren't they removed and that cmake option also removed?

Hi, I'm trying to do a build and install on Windows 10 with Visual Studio 2015 Community Edition for the X86 and ARM targets, from the current release_40 branch. While compilation completes without error, the INSTALL target fails with the following error: 54> CMake Error at projects/compiler-rt/lib/builtins/cmake_install.cmake:34 (file): 54> file INSTALL cannot find 54>