similar to: [LLVMdev] Truncate float to int?

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

The LLVM IR reference manual states, for fptosi: "The ‘fptosi’ instruction converts its floating-point <http://llvm.org/docs/LangRef.html#t-floating> operand into the nearest (rounding towards zero) signed integer value." I interpreted this to mean that it rounds: The nearest integer to 0.3 is 0. The nearest integer to 0.9 is 1. The nearest integer to 0.5 is either 0 or 1. And

If fptosi takes 0.9 -> 0, then that is not 'rounding' in any sense I'm aware of (IEEE754 or otherwise). Rounding (in the IEE754 sense) determines how a number is converted when it is halfway between two candidate results. (see round(), ceil(), floor()). fptosi seems to model the behavior of a C cast from float to int, which truncates the fractional bits (as in trunc()). Steve

On 8 January 2018 at 11:15, Kaylor, Andrew via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Hi Kevin, > > Thanks for reaching out about this, and thanks especially for offering to > help. I've had some other priorities that have prevented me from making > progress on this recently. > > As far as I know, there is no support at all in clang for handling the >

On 01/08/2018 07:06 PM, Richard Smith via llvm-dev wrote: > On 8 January 2018 at 11:15, Kaylor, Andrew via llvm-dev > <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote: > > Hi Kevin, > > Thanks for reaching out about this, and thanks especially for > offering to help. I've had some other priorities that have > prevented

On 8 Jan 2018 19:50, "Hal Finkel via cfe-dev" <cfe-dev at lists.llvm.org> wrote: On 01/08/2018 07:06 PM, Richard Smith via llvm-dev wrote: On 8 January 2018 at 11:15, Kaylor, Andrew via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Hi Kevin, > > Thanks for reaching out about this, and thanks especially for offering to > help. I've had some other

Hi Kevin, Thanks for reaching out about this, and thanks especially for offering to help. I've had some other priorities that have prevented me from making progress on this recently. As far as I know, there is no support at all in clang for handling the FENV_ACCESS pragma. I have a sample patch somewhere that I created to demonstrate how the front end would create the constrained intrinsics

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

Hi, Lately we have come to realize how undef makes our life complicated.. Therefore in this email we propose to change the behavior of a few instruction to yield poison instead of undef in error cases. This follows the suggestion of Eli in https://reviews.llvm.org/D33654. Why is undef so bad? - I believe it's not possible to make newgvn correct with undef. See for example the discussion

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

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 Sarath, It would have really helped if you had removed the commented out code and inlined the calls to your homemade helper functions before sending it... You are doing this, in LLVM IR: %0 = getelementptr %Value* %firstArg, i32 0 ; i8** %1 = load i8** %0 ; i8* %2 = bitcast i8* %1 to i64* %3 = getelementptr %Value* %secondArg, i32 0 ; i8** %4 = load i8** %3; i8* %5 = bitcast i8* %4 to i64*

Yeah, that's the fault...got the answer...... Thanks James for the help... Struggling with this for so many days....... On Thu, Sep 22, 2011 at 4:02 PM, James Molloy <James.Molloy at arm.com> wrote: > Hi Sarath,**** > > ** ** > > It would have really helped if you had removed the commented out code and > inlined the calls to your homemade helper functions before

On Thu, Sep 22, 2011 at 3:46 PM, sarath chandra <sarathcse19 at gmail.com>wrote: > Hi James, > > First i converted the void * to int* and then did FPToSI...then did SHL...( > because CreateShl only accepts integers... i pointer casted it to int64 type > first)... Below is the code snippet.... > > > lhs = mBuilder.CreateStructGEP(firstArg, 0); > lhs =

On Sep 22, 2011, at 3:32 AM, James Molloy wrote: > It’s in trouble by this point because it needs to do a fptosi on a double operand, but you’ve got an i64 operand and you can’t reinterpret-cast ints to floats in LLVM IR (AFAIK) You can bitcast ints to floats and vice-versa if they're the same size — for example, i32 to float and i64 to double. John.

> On Sep 4, 2020, at 2:40 PM, Neil Nelson via llvm-dev <llvm-dev at lists.llvm.org> wrote: > >> If fptosi takes 0.9 -> 0, then that is not 'rounding' in any sense I'm aware of (IEEE754 or otherwise). >> Rounding (in the IEE754 sense) determines how a number is converted when it is halfway between two >> candidate results. (see round(), ceil(),

It seems that tail duplication can make a reducible CFG irreducible (example below). Is that intentional? Are there other optimizations that have that property? Is irreducibility a problem for existing LLVM passes? It looks like there was once an open project for a pass to make irreducible graphs reducible. Was that ever implemented? - Mark ; "opt -inline -tailduplicate" makes an

Good to know, thanks. The docs are slightly hazy on that - they do mention type-to-type if same size, but the examples are only between pointers and integers, not floats. Would it be worthwhile my updating the documentation to explicitly state that or is it just me? Cheers, James -----Original Message----- From: John McCall [mailto:rjmccall at apple.com] Sent: 23 September 2011 00:06 To: James

Hi everyone! The fptoui/fptosi instructions are currently specified to return a poison value if the rounded-towards-zero floating point number cannot be represented by the target integer type. The motivation for this behavior is that overflowing float to int casts in C are undefined behavior. However, many newer languages prefer to have a float to integer cast that is well-defined for all input