similar to: [LLVMdev] emit after gvn pass?

On Wednesday 05 May 2010 12:00:18 nonpoly wrote: > Hello again, > Just wondering if there is a flag I can pass when compiling with > llvm-gcc that can emit the llvm IR after the gvn pass (want to see the IR > after dead code elimination/redundancy elimination). If so, will other > passes be performed as well? I really just want to see the IR after the > eliminations only, if

Wow, thanks for the super fast reply! I was asking about llvm-gcc because I want to be able to work with code that compiles on GCC (since there is so much already out there), but in an intermediate form. So I take it that clang plans on being able to compile code that compiles on GCC? I'm assuming that's what they mean by "GCC compatibility" on http://clang.llvm.org/ ;p On a

Introduction ============ I'm currently in the middle of what initially looked to be a simple change in GVN but is turning out to have unexpected consequences that are turning out to be quite difficult to resolve, so I thought I'd send out an RFC to make sure that I'm not barking up the wrong tree with how I'm trying to do this. Motivation and current behaviour

Does LLVM have loop multiversioning ? it seems it does not with clang++ -O3 -mllvm -debug-pass=Arguments program.c -c bash-4.1$ clang++ -O3 -mllvm -debug-pass=Arguments fast_algorithms.c -c clang-3.6: warning: treating 'c' input as 'c++' when in C++ mode, this behavior is deprecated Pass Arguments: -datalayout -notti -basictti -x86tti -targetlibinfo -no-aa -tbaa -scoped-noalias

Hello, I found that GVN doesn't promote identical sequence of instructions in if and else branch to their common predecessors. For example, for the following code snippet pred: … br i1 %cmp, label %if, label %else if: %incdec.ptr.1 = getelementptr inbounds i8, i8* %ptr, i64 1 %cast1 = ptrtoint i8* %incdec.ptr.1 to i64 … else: %incdec.ptr.2 = getelementptr inbounds i8, i8* %ptr,

and by "right thing" i mean it can hoist if you want and it can prove it will not extend the live range. Note that VBE (very busy expressions) is a code size optimization only. It does not save time. On Tue, Feb 9, 2016 at 12:26 PM, Daniel Berlin <dberlin at dberlin.org> wrote: > This GVN does not do that, this is correct. It is a very simple GVN. All > phi nodes are

There is a phi-node "%phi = phi i64 [%cast1, %if], [%cast2, %else]" in the common successor. The actual control flow is a bit more complex, but there is a common successor block, and %cast1 and %cast2 are the two values that the phi node in the common successor takes. Does the existence of the phi node affect optimization? Thanks, Taewook From: <mats.o.petersson at

Hi, This is Ariel from the Rust team again. I am having another pass ordering issue. Looking at the pass manager at https://github.com/llvm-mirror/llvm/blob/7034870f30320d6fbc74effff539d946018cd00a/lib/Transforms/IPO/PassManagerBuilder.cpp (the early SimplifyCfg now doesn't sink stores anymore! I can't wait until I can get to use that in rustc!) I find that the loop optimization group

On May 3, 2011, at 3:25 PM, Arushi Aggarwal wrote: > Hi, > > GVN seems to be running in an infinite loop on my example. I have attached the output of one iteration. I cant seem to reduce the testcase either. > > Any pointers to how to reduce the test case. Bugzilla can reduce testcases that cause infinite loops (it has a -timeout flag), I'd try it. Even if this doesn't

Hello, I was hoping to get some clarification on the aim of the GVN pass. I have been reading a bit about global value numbering, and from what I understand, there are polynomial time algorithms for removing duplicate computations from loops[1]. I have an example program[2] which computes the sum of an array twice, in two separate accumulators. Here, sum0 and sum1 are both sums of the array A.

Hi, GVN seems to be running in an infinite loop on my example. I have attached the output of one iteration. I cant seem to reduce the testcase either. Any pointers to how to reduce the test case. THanks, Arushi GVN iteration: 8 GVN WIDENED LOAD: %0 = load i8* getelementptr inbounds (%struct.CHESS_POSITION* @search, i64 0, i32 23), align 2, !dbg !875 TO: %1 = load i16* bitcast (i8*

Hi, I've noticed that alias analysis queries arising from GVN do not use the results from GlobalsAA. The last call to AAResultsWrapperPass::runOnFunction() before GVN does not add GlobalsAAWrapperPass due to unavailability. This leads to the alias queries from GVN not having any globals mod-ref info. Is this a known issue? and is there any way to have globals mod-ref info available for GVN?

On Tue, Apr 10, 2018 at 3:09 PM, Daniel Berlin via llvm-dev < llvm-dev at lists.llvm.org> wrote: > > > On Tue, Apr 10, 2018 at 10:28 AM, Friedman, Eli via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> On 4/9/2018 8:19 PM, Jeehoon Kang via llvm-dev wrote: >> >> Dear llvm-dev, >> >> >> Hi! We're collecting mis-compilation

I've heard a few times, "GVN uses too much memory." The real fix is probably a rewrite of some sort, but that's not what this email is about. I have a few patches that should *incrementally* reduce its memory usage. Keyword being "should", because I haven't observed an improvement... in fact, I haven't seen it using much memory at all. Does anyone have a

On 4/9/2018 8:19 PM, Jeehoon Kang via llvm-dev wrote: > Dear llvm-dev, > > > Hi! We're collecting mis-compilation bugs in gvn and mem2reg since > 3.7.1.  Specifically, We're interested in bugs in the following files: > > llvm/lib/Transforms/Scalar/GVN.cpp > llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp 3.7 was released over two years ago; there have been

On Tue, Apr 10, 2018 at 10:28 AM, Friedman, Eli via llvm-dev < llvm-dev at lists.llvm.org> wrote: > On 4/9/2018 8:19 PM, Jeehoon Kang via llvm-dev wrote: > > Dear llvm-dev, > > > Hi! We're collecting mis-compilation bugs in gvn and mem2reg since > 3.7.1. Specifically, We're interested in bugs in the following files: > > llvm/lib/Transforms/Scalar/GVN.cpp

Hello, We are now facing a bug caused by the GVN pass, only part of the code was optimized. I have found that the problem is cause by an Limit in lib/Analysis/MemoryDependenceAnalysis.cpp 00055 static cl::opt<unsigned> BlockScanLimit( 00056 "memdep-block-scan-limit", cl::Hidden, cl::init(100), 00057 cl::desc("The number of instructions to scan in a block in

----- Original Message ----- > From: "Daniel Berlin via llvm-dev" <llvm-dev at lists.llvm.org> > To: "Amos Robinson" <amos.robinson at gmail.com> > Cc: "llvm-dev" <llvm-dev at lists.llvm.org> > Sent: Tuesday, May 3, 2016 7:39:54 PM > Subject: Re: [llvm-dev] GVN pass: does global value numbering remove > duplicate computations in

Might have to do with GVN's PRE (partial redundancy elimination), which tends to increase code size. H. ----- Original Message ----- From: Abhinash Jain Sent: 09/22/13 01:17 AM To: llvmdev at cs.uiuc.edu Subject: [LLVMdev] Why total number of store instructions increased in case of gvn with reg2mem? Below are the 4 cases out of which for the first 3 cases am able to understand the variation

Hi James, Thanks for the help. From the log, I could infer that SLP vectorizer is not preserving alias analysis, preventing GVN from getting the info. Although the first function to get compiled has GlobalsAA available during GVN, rest of them do not as SLP vectorizer run on that function invalidates GlobalsAA which is a module pass. Is there a way to force re-computation of a particular