similar to: carries_dependency attribute

If carries_dependency affects semantics, then it should not be an attribute. The original design, or at least my understanding of it, was that it not have semantics; it was only a suggestion to the compiler that it should preserve dependencies instead of inserting a fence at the call site. Dependency-based ordering would be preserved in either case. But I think we're moving away from that

And again... LLVM_BUILD_LLVM_DYLIB:BOOL=ON LLVM_LINK_LLVM_DYLIB:BOOL=ON This one is the good one... maybe. On Tue, Sep 6, 2016 at 11:35 PM, Alexandre Isoard < alexandre.isoard at gmail.com> wrote: > That is because I mistyped it: > LLVM_ENABLE_LLVM_DYLIB:BOOL=ON > LLVM_LINK_LLVM_DYLIB:BOOL=ON > > On Tue, Sep 6, 2016 at 11:31 PM, Wink Saville <wink at saville.com>

Hi Alexandre, On Wed, Oct 19, 2016 at 11:19 AM, Alexandre Isoard <alexandre.isoard at gmail.com> wrote: > I am probably missing something important, but what I mean is that you can > always convert: > > %y = xor %x, %x > to > %y = 0 > > Regardless of if %x is/might be an undef. That is, consider that reading %x > any number of times always give the value of its

On Fri, Nov 3, 2017 at 5:39 PM, Hal Finkel <hfinkel at anl.gov> wrote: > > On 11/03/2017 07:20 PM, Alexandre Isoard via llvm-dev wrote: > > Hello, > > I am not sure about the semantic (if any) of returns_twice and noreturn > attributes. > > int fork() __attribute__((returns_twice)); > void join(int) __attribute__((noreturn)); > > int f(int n) { > int

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

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

On Fri, Feb 19, 2016 at 09:15:16PM -0500, Tony V E wrote: > There's at least one easy answer in there: > > > ‎If implementations must support annotation, what form should that > annotation take?  P0190R0 recommends the [[carries_dependency]] > attribute, but I am not picky as long as it can be (1) applied > to all relevant pointer-like objects and (2) used in C as well

On Tue, Sep 6, 2016 at 3:05 PM, Alexandre Isoard <alexandre.isoard at gmail.com> wrote: > LLVM_ENABLE_DYLIB Where/when/how do you specify LLVM_ENABLE_DYLIB and LLVM_LINK_DYLIB? I tried the following on the cmake command line: $ cmake -G Ninja .. -DCMAKE_INSTALL_PREFIX=/home/wink/opt/llvm -DLLVM_ENABLE_DYLIB=true -DLLVM_LINK_DYLIB=true And got: ... -- Performing Test

Hello, Yes? Where is allActive defined, I couldn't find it. Basically, a BB is control divergent if it's execution depends on a branch that itself depends on a divergent ssa value. On Fri, Jul 21, 2017 at 4:13 PM, Zaks, Ayal <ayal.zaks at intel.com> wrote: > What would be the definition of “isControlDivergent(BasicBlock*)”; the > complementary of “allActive(BasicBlock*)” –

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

I did not observe any assertion. In addition, the documentation ( https://llvm.org/docs/LangRef.html#undefined-values) says: The string ‘undef’ can be used anywhere a constant is expected, and indicates that the user of the value may receive an unspecified bit-pattern. Undefined values may be of any type (other than ‘label’ or ‘ void’) and be used anywhere a constant is permitted. Either way,

Hello fellow LLVM developers, I was wondering about the semantic of aliasing. Here are some examples where I am not sure if the two stores aliases: Example 1: for (int i = 2; i < n; ++i) { store A[i]; store A[i-2]; } Example 2: for (int i = 2; i < n; ++i) store A[i]; for (int i = 2; i < n; ++i) store A[i-2]; In the example 1, they do not alias in a single iteration, but they

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. >

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?

Hello! A proposal (quaintly identified as P0190R0) for a new memory_order_consume definition may be found here: http://www2.rdrop.com/users/paulmck/submission/consume.2016.02.10b.pdf As requested at the October C++ Standards Committee meeting, this is a follow-on to P0098R1 that picks one alternative and describes it in detail. This approach focuses on existing practice, with the goal of

Hello, I am not sure about the semantic (if any) of returns_twice and noreturn attributes. int fork() __attribute__((returns_twice)); void join(int) __attribute__((noreturn)); int f(int n) { int t = fork(); n++; if (t != 0) join(t); return n; } Produces the following LLVM IR: ; Function Attrs: nounwind uwtable define i32 @f(i32 %n) local_unnamed_addr #0 { entry: %call = call i32

On Wed, Aug 24, 2016 at 10:11 AM, Renato Golin <renato.golin at linaro.org> wrote: > On 24 August 2016 at 08:48, Alexandre Isoard via llvm-dev > <llvm-dev at lists.llvm.org> wrote: > > I am probably stating the obvious, but if the function is side-effect > free > > (onlyReadsMemory) it is valid to remove it. > > > > But I am guessing that does not

Hello, I assumed SCEV purpose was to be a normal form, but then I wondered which one of those is the normal form: (zext i16 (trunc i32 %a to i16) to i32) vs (-((%a /u 65536) *u 65536) + %a) The first one is nice for interval analysis, and known bit analysis. The second one is nice when plugged into gep of 2d arrays. -- *Alexandre Isoard* -------------- next part -------------- An HTML

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