similar to: trunc nsw/nuw?

Hi, > Hi Alexandre, > > LLVM currently doesn't have trunc nsw/nuw, no. > Which frontend would emit such instructions? Any application in mind? > Just asking because if no frontend could emit those, then the motivation to > add nsw/nuw support to trunc would be very low I guess. I think the clang frontend could use that to allow better static analysis of integer overflows on

On Wed, Jul 5, 2017 at 3:59 PM, Hal Finkel via llvm-dev < llvm-dev at lists.llvm.org> wrote: > > On 07/04/2017 01:41 AM, Dr.-Ing. Christoph Cullmann via llvm-dev wrote: > >> Hi, >> >> Hi Alexandre, >>> >>> LLVM currently doesn't have trunc nsw/nuw, no. >>> Which frontend would emit such instructions? Any application in mind?

On 07/05/2017 03:10 PM, Alexandre Isoard wrote: > Ah, ok. I read it wrong. In *neither* case it is UB. > > Hum, can an implementation define it as UB? :-) Nope :-) The only case I've thought of where we could add these for C++ would be on conversions to (most) enums (because they used signed underlying types and the out-of-bounds mapping won't generally be one of the allowed

According to 6.3.1.3/3 of the C standard (I didn't check C++): "3 Otherwise, the new type is signed and the value cannot be represented in it; either the result is implementation-defined or an implementation-defined signal is raised." I *think* that means that IF a signal is raised then the signal raised could be one that you can't guarantee to be able to return from

Hi, Even if there are no ways in which a *frontend* can produce nsw truncs, it may still be useful to have if optimization passes can usefully attach nsw to truncates (after proving the truncates don't "overflow"). For instance in %a = ashr i64 %v, i32 33 %t = trunc %a to i32 the trunc can be marked nsw. However, the burden of proof here is to show that we can do some useful

On Wednesday, August 18, 2010 11:49:28 am Anton Korobeynikov wrote: > Hello > > > Is there some official git repository to clone from? > > Not yet, but probably there will be something pretty soon. > Right now there are some unofficial mirrors at repo.or.cz and github Ok, then I will try to wait until the official is ready. If I now start that with an unofficial one, I will

Hi, we want to use LLVM together with clang internally for preprocessing and Co. Therefor we would like to integrate it in our buildsystem. The nicest thing for us would be a local git repository mirror, to allow us to easily create own branches and Co. Is there some official git repository to clone from? I looked up the archives and seen that creating own clones of the SVN via git svn is not

Hi, I want to use llvm::Value::print to output the assembly strings for llvm::Instructions inside a rather large llvm::Module (linked module with lots of types/...). I started with plain ::print and switched over to http://llvm.org/docs/doxygen/html/classllvm_1_1Value.html#a04e6fc765eeb0c4c90ac5d55113db116 with a ModuleSlotTracker I pass in myself to avoid some complexity. Still now I have

Dear Thomas, > Hi Christoph, > > maybe there is a way of caching the print outputs and output them at the > end of the program execution? > So, your real application do not have this kind of bottle neck. this is a valid idea, thought the problem is: I output all things only "once" and I even output it like: 1) load module 2) go over functions 3) output all blocks with

Hello > Is there some official git repository to clone from? Not yet, but probably there will be something pretty soon. Right now there are some unofficial mirrors at repo.or.cz and github -- With best regards, Anton Korobeynikov Faculty of Mathematics and Mechanics, Saint Petersburg State University

Dear testers, 5.0.0-rc3 was just tagged. This is a release candidate in the real sense: if nothing bad comes up in testing, this is what the release is going to look like. Please build, test and upload binaries to the sftp (use the /data/testers-uploads/ directory) and let me know what issues remain. I know we're a little bit behind schedule, but hopefully we can get to 'final'

Hi, it seems that e.g. on Windows, where the filename encoding is not UTF-8, it is impossible to use any filenames containing e.g. german umlauts or chinese characters, because the in LLVM used encoding collides with the encoding used by the OS. There is a open bug for this http://llvm.org/bugs/show_bug.cgi?id=10348 It seems there were patches submitted to fix it, but they were never applied as

Is that why we do not deduce +<nsw> from "add nsw" either? Is that an intrinsic limitation of creating a context-invariant expressions from a Value* or is that a limitation of our implementation (our unification not considering the nsw flags)? On Wed, Aug 15, 2018 at 12:39 PM Friedman, Eli <efriedma at codeaurora.org> wrote: > On 8/15/2018 12:21 PM, Alexandre Isoard via

I'm not sure I understand the poison/undef/UB distinctions. But on this example: define i32 @func(i1 zeroext %b, i32 %x, i32 %y) { > entry: > %adds = add nsw i32 %x, %y > %addu = add nuw i32 %x, %y > %cond = select i1 %b, i32 %adds, i32 %addu > ret i32 %cond > } It is important to not propagate the nsw/nuw between the two SCEV expressions (which unification would

Ok. To go back to the original issue, would it be meaningful to add a SCEVUMax(0, BTC) on the final BTC computed by SCEV? So that it does not use "negative values"? On Wed, Aug 15, 2018 at 2:40 PM Friedman, Eli <efriedma at codeaurora.org> wrote: > On 8/15/2018 2:27 PM, Alexandre Isoard wrote: > > I'm not sure I understand the poison/undef/UB distinctions. >

Hello, If I run clang on the following code: void func(unsigned n) { > for (unsigned long x = 1; x < n; ++x) > dummy(x); > } I get the following llvm ir: define void @func(i32 %n) { > entry: > %conv = zext i32 %n to i64 > %cmp5 = icmp ugt i32 %n, 1 > br i1 %cmp5, label %for.body, label %for.cond.cleanup > for.cond.cleanup:

Note that there is a slight difficulty due to the fact that we "sink" the trunc: (zext i16 {0,+,1}<%bb> to i32) + (65536 * ({0,+,1}<nuw><%bb> /u 65536) Here the recurrence lost it's <nuw> and got reduced to a i16 (on the left), but not on the right. But we can prove: - that (zext i16 {0,+,1}<%bb> to i32) has the same 16 LSB than (i32

Hello, I noticed that our SCEVUDiv does not simplify anything when the RHS is not a constant. Is that because there is a potential issue with division by zero being simplified? For instance, would it be okay to simplify: ((%i * %n)<nuw> /u %n) into: %i The way I see it, if %n is 0, then that division is undefined and we can "define it", at will, as being %i. Would that make

On Aug 11, 2011, at 7:31 AM, Florian Merz wrote: > If we had nsw and nuw flags for truncations we'd know when to check for this > kind of overflow and when not. The compiler likely doesn't need these flags and > can still ignore them, for us they would be useful. Duncan's point is that this is totally different from the semantics of nsw/nuw on other instructions, which

On Aug 11, 2011, at19:34, John McCall wrote: > On Aug 11, 2011, at 7:31 AM, Florian Merz wrote: > > If we had nsw and nuw flags for truncations we'd know when to check for > > this kind of overflow and when not. The compiler likely doesn't need > > these flags and can still ignore them, for us they would be useful. > > Duncan's point is that this is totally