similar to: The semantics of the fptrunc instruction with an example of incorrect optimisation

Howdy all, I've been playing around with programs that use the C11 fenv.h. It seems that, currently, the LLVM compiler does not regard to the exception-flag side-effects of floating point operations? When run on my macbook, the example code on http://en.cppreference.com/w/c/numeric/fenv/FE_exceptions does not print all the expected exceptions. Other examples: void foo() {

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,

Hi, What is the rounding mode for the fptrunc instruction? Round to zero? Round to nearest? Or undefined? Regards, Jon

Hi: I am trying to implement interval arithmetic through llvm. I have a problem with the rounding mode with llvm.experimental.constrained.cos I have two pieces of codes: ; Function Attrs: norecurse nounwind readnone ssp uwtable define double @cosine_down(double returned) local_unnamed_addr #0 {   ; call the llvm intrinsic to perform downward cosine

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

On Mon, 31 Mar 2008, Jon Sargeant wrote: > The fptrunc instruction states "If the value cannot fit within the > destination type, ty2, then the results are undefined." This is fine, but > what about other floating-point operations that can overflow? For example, > does 'mul double 1.0e300, 1.0e300' produce +infinity or is it undefined? It is defined by IEEE to

The fptrunc instruction states "If the value cannot fit within the destination type, ty2, then the results are undefined." This is fine, but what about other floating-point operations that can overflow? For example, does 'mul double 1.0e300, 1.0e300' produce +infinity or is it undefined? I think LLVM should treat floating-point overflows consistently. On a similar note,

For the following C code __fp16 x, y, z, w; void foo() { x = y + z; x = x + w; } clang produces IR that extends each operand to float and then truncates to half before assigning to x. Like this define dso_local void @foo() #0 !dbg !18 { %1 = load half, half* @y, align 2, !dbg !21 %2 = fpext half %1 to float, !dbg !21 %3 = load half, half* @z, align 2, !dbg !22 %4 = fpext half %3 to float, !dbg

Thanks Eli. I forgot to bring up the strict FP questions which I was working on when I found this. If we're in a strict FP function, do the fp_to_f16/f16_to_fp emitted by promoting load/store/bitcast need to be strict versions of fp_to_f16/f16_to_fp. And if so where do we get the chain, especially for the bitcast case which isn't a chained node. ~Craig On Tue, Dec 10, 2019 at 3:18 PM

Hi, The LangRef says this about fptrunc: "The ‘fptrunc‘ instruction truncates a value from a larger floating point type to a smaller floating point type. If the value cannot fit within the destination type, ty2, then the results are undefined." What does it mean for the value to "fit within the destination type"? For instance, is the value of %Inf = fptrunc double

    Thank you Kevin!!!    If I use fptrunc and bitcast realise NEON vcvtt ( I can sure, "fptrunc  double %tmp to float" is right, but "fptrunc float %tmp to half" is wrong). My target platform is MIPS.  The command as following: NEON:            vcvtt.f16.f32 s2, s0 llvm Code: %Vt_2 = load float* %VFP_s0, align 4 %Vt3_1 = fptrunc float %Vt_2 to half %Vt4_1 = bitcast half

On 07/09/2014 12:41 PM, Matt Arsenault wrote: > On 07/09/2014 03:30 PM, yalong at multicorewareinc.com wrote: >> Thank you Kevin!!! >> If I use fptrunc and bitcast realise NEON vcvtt ( I can sure, >> "fptrunc double %tmp to float" is right, but "fptrunc float %tmp to >> half" is wrong). My target platform is MIPS. The command as following:

Newbie question here: what's the best way to truncate a float to a signed int? The fptosi instruction rounds, and the fptrunc instruction simply truncates from a large float type to a smaller float type. Mark

Hi Daniel,    Thank you your replying.     Yes, the problem is about MIPS backend. You give me this message "There is limited support for the <8 x f16> type when MSA (MIPS SIMD Architecture) is enabled but even then scalar half-precision is not currently supported."  Could you give me some official link or some evidence? Thank you very much. Robin yalong at multicorewareinc.com

On Jul 14, 2014, at 7:23 AM, Tom Stellard <tom at stellard.net> wrote: > On Mon, Jul 14, 2014 at 01:08:54PM +0100, Tim Northover wrote: >> Hi all, >> >> What do people think of doing away with the @llvm.convert.to.fp16 and >> @llvm.convert.from.fp16 intrinsics, in favour of using "half" and >> fpext/fptrunc? [1] >> > > I am in favor

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

On Tue, Jun 3, 2008 at 11:32 AM, Mark Leone <markleone at gmail.com> wrote: > Newbie question here: what's the best way to truncate a float to a > signed int? The fptosi instruction rounds, and the fptrunc > instruction simply truncates from a large float type to a smaller > float type. fptosi is equivalent to a C cast from float to int. -Eli

Hi, I have some IR module from random generation (mostly ineffective instructions). It has a function with void return, and two function arguments where one is a reference. Therefore, I expect every instruction not altering the value at the 2nd arguments address should be ineffective. Here is the function definition (see below for full ll): define void @_Z27entityMainDataInputCallbackdRd(double