similar to: [LLVMdev] AtomicRMW Additions

Hi! It is said in http://llvm.org/docs/LangRef.html#i_atomicrmw there is an atomicrmw opcode. But: store i8 %2, i8* %tape1.sub %3 = atomicrmw add i8* %tape1.sub, i8 1 acquire fails with: llc: test.bc:13:9: error: expected instruction opcode %3 = atomicrmw add i8* %tape1.sub, i8 1 acquire How can I do *ptr = *ptr + val with LLVM ?

Looking further during down time at the dev meeting today, it actually seems that PTX atom.* and red.* intrinsics map extremely naturally onto the LLVM atomicrmw and cmpxchg instructions. The biggest issue is that a subset of things expressible with these LLVM instructions do not trivially map to PTX, and the range of things naturally supported depends on the features of a given target. With

Greetings everyone, I am working on Aarch64 LSE out-of-line atomics support in LLVM, porting this GCC series: https://gcc.gnu.org/legacy-ml/gcc-patches/2019-09/msg01034.html After local design experiments I've got some questions about upstream-suitable ways of implementation. More specifically: 1. Pass to expand atomics to library helper functions calls. These helpers test for the presence

Right now, the atomics implementation in clang is a bit of a mess. It has three basically completely distinct code-paths: There's the legacy __sync_* builtins, which clang lowers directly to atomic IR instructions. Then, the llvm atomic IR instructions themselves can sometimes emit libcalls to __sync_* library functions (which are basically undocumented, and users are often responsible for

On 12/11/2015 01:29 PM, James Y Knight wrote: > > On Fri, Dec 11, 2015 at 3:05 PM, Philip Reames via llvm-dev > <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote: > >> One open question I don't know the answer to: Are there any >> special semantics required from floating point stores which >> aren't met

On Mon, Oct 31, 2011 at 3:15 PM, Jonathan Ragan-Kelley <jrk at csail.mit.edu>wrote: > I notice that there is not currently any intrinsic support for atomics in > the PTX backend. Is this on the roadmap? Should it be as easy to add as it > seems (plumbing through just like the thread ID instructions, &c.)? The > obvious difference is that these ops have side effects. > It

I notice that there is not currently any intrinsic support for atomics in the PTX backend. Is this on the roadmap? Should it be as easy to add as it seems (plumbing through just like the thread ID instructions, &c.)? The obvious difference is that these ops have side effects. -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type:

Hello, I'm wondering how I can create an atomic load and add instruction for floating point values. If I use IRBuilder::CreateAtomicRMW() I get the error message: "atomicrmw operand must have integer type". I am using LLVM 3.4 and the only system I need to support is x86.

Hi, I've been looking at improving atomicrmw & cmpxchg code more, particularly on architectures using the load-linked/store-conditional model. The summary is that current expansion for cmpxchg seems to happen too late for LLVM to make meaningful use of the opportunities it provides. I'd like to move it earlier and express it in terms of a first-class pair of "load linked"

# RFC: Atomic LL/SC loops in LLVM revisited ## Summary This proposal gives a brief overview of the challenges of lowering to LL/SC loops and details the approach I am taking for RISC-V. Beyond getting feedback on that work, my intention is to find consensus on moving other backends towards a similar approach and sharing common code where feasible. Scroll down to 'Questions' for a summary

I'm working on getting the LLVM/projects/Test-Suite/UnitTest to compile for a target that I am developing. There is an example: AtomicOps, that uses calls to: __sync_fetch_and_add __sync_val_compare_and_swap __sync_lock_test_and_set These get converted into llvm IR operations like: atomicrmw cmpxchg Is there any way to keep these as function calls, as they are easier to map to the

I don't have much of substance to add, but I will say that I like the proposal (I too prefer Alternative A). When adding C11 atomic support for hexagon, I found it surprising that support for the __sync_* was implemented completely differently than the C11 atomics. On 1/27/2016 1:55 PM, James Knight via llvm-dev wrote: > Right now, the atomics implementation in clang is a bit of a

On 14 June 2018 at 10:28, Tim Northover via llvm-dev <llvm-dev at lists.llvm.org> wrote: >> * I'd like to see ARM+AArch64+Hexagon move away from the problematic >> expansion in IR and to have that code deleted from AtomicExpandPass. Are >> there any objections? > > I think it would be a great shame and I'd like to avoid it if at all > possible, though

On 12/11/2015 12:05 AM, JF Bastien wrote: > On Fri, Dec 11, 2015 at 3:22 AM, Philip Reames via llvm-dev > <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote: > > Currently, we limit atomic loads and stores to either pointer or > integer types. I would like to propose that we extend this to > allow both floating point and vector types

On Sun, Jul 31, 2011 at 12:49 PM, Jianzhou Zhao <jianzhou at seas.upenn.edu> wrote: > I noticed the patch was already merged into the current LLVM language > reference manual with new memory instructions, fence, cmpxchg and > atomicrmw. Will the instructions be available in LLVM 3.0? Hopefully, yes; the implementation is in progress. -Eli

Forgive me if I'm missing something obvious, but it seems that a number of core instructions—I'm specifically running in to `atomicrmw`, `fence`, and `cmpxchg` at the moment—cannot be constructed from the C bindings, and are therefore also inaccessible to the OCaml bindings. There are opcodes for each of these in the llvm-c/Core.h, but there seems to be no way to construct them. Is there

Problem LLVM's memory model for NonAtomic accesses is generally fairly weak, but explicitly disallows inserting stores that didn't occur in the original program.  This is required for any potentially shared location, but is overkill for any memory location which is provably only accessed by a single thread. My particular motivating example is a single thread private field in our

I finally got around to adding these. The patch is posted in a pull request on my copy of llvm.git: https://github.com/jrk/llvm/pull/3 and a simple test with OCaml is here: https://gist.github.com/3948460 Feedback welcome. On Sep 14, 2012, at 7:53 PM, Jonathan Ragan-Kelley <jrk at csail.mit.edu> wrote: > Forgive me if I'm missing something obvious, but it seems that a >

Hi All, With the "https://gcc.godbolt.org/z/yBYTrd" case . the atomic is converted to non atomic ops for x86 like from xchg dword ptr [100], eax to mov dword ptr [100], 1 the pass is responsible for this tranformation was instCombine i.e InstCombiner::visitAtomicRMWInst which converts the IR like %0 = atomicrmw xchg i32* inttoptr (i64 100 to i32*), i32 1 monotonic to store

Hi Johannes, > I am especially curious where you get your data from. Tapir [0] (and to > some degree PIR [1]) have shown that, counterintuitively, only a few changes > to LLVM passes are needed. Tapir was recently used in an MIT class with a > lot of students and it seemed to work well with only minimal changes > to analysis and especially transformation passes. TAPIR is an