similar to: Programmatically Toggle Specific LLVM Optimizations

Hi Michael! Thanks for your reply. I managed to add a small amount of code to PassManager to have this feature implemented. One can now turn off a pass by doing opt -disablepass=licm or clang -mllvm -disablepass=licm to turn off, for example, loop invariant code motion. I programmed the command line option to be really hidden. This maybe a useful thing to have in the trunk for people who

I'm working on a whole program optimizer that uses LLVM as a library, and one of the things I want to do is eliminate dead global functions and variables even when they are not local to a module. (This understandably doesn't happen by default because the optimizer has to assume it could be compiling a library rather than a program.) I've actually written a function to do this, but

Hi folks, I am wondering about the relationship clang, opt and llc. I understand that this has been asked, e.g., http://stackoverflow.com/questions/40350990/relationship-between-clang-opt-llc-and-llvm-linker. Sorry for posting a similar question again, but I still have something that hasn't been resolved yet. More specifically I am wondering about the following two approaches compiling

Hi, I would like to run the -O1 pass sequence followed by -reg2mem from an out of tree project which uses llvm. I am using the following code snippet to do so but in some cases, my method is also vectorising the code, which doesn't happen when running the same sequence(-S -O1 -reg2mem) through opt. Can someone please help me find what I am missing? Thanks, Akash. *

> On Apr 10, 2017, at 5:21 PM, Craig Topper via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > clang -O0 does not disable all optimization passes modify the IR.; In fact it causes most functions to get tagged with noinline to prevent inlinining It also disable lifetime instrinsics emission and TBAA, etc. > > What you really need to do is > > clang -O3 -c

It's really nice of you pointing out the -Xclang option, it makes things much easier. I really appreciate your help! Best, Peizhao On Mon, Apr 10, 2017 at 10:12 PM, Mehdi Amini <mehdi.amini at apple.com> wrote: > > On Apr 10, 2017, at 5:21 PM, Craig Topper via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > > clang -O0 does not disable all optimization passes

Revision 190916 Commit message: "Lift alignment restrictions for load/store folding on VINSERTF128/VEXTRACTF128. Fixes PR17268." Actual contents of the commit includes Index: tools/opt/opt.cpp =================================================================== --- tools/opt/opt.cpp (revision 190915) +++ tools/opt/opt.cpp (revision 190916) @@ -462,6 +462,7 @@

I tried the following on LULESH1.0 serial version ( https://codesign.llnl.gov/lulesh/LULESH.cc) 1. clang++ -O3 LULESH.cc; ./a.out 20 Runtime: 9.487353 second 2. clang++ -O0 -Xclang -disable-llvm-passes -c -emit-llvm -o a.bc LULESH.cc; opt -O3 a.bc -o b.bc; llc -O3 -filetype=obj b.bc -o b.o ; clang++ b.o -o b.out; ./b.out 20 Runtime: 24.15 seconds 3. clang++ -O3 -Xclang -disable-llvm-passes -c

On Mon, May 09, 2016 at 01:07:07PM -0700, Mehdi Amini via llvm-dev wrote: > > > On May 9, 2016, at 10:43 AM, Ricardo Nobre via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > > > Hi, > > > > I'm a PhD student doing phase ordering as part of my PhD topic and I would like to ask some questions about LLVM. > > > > Executing the following

Hi, How can I dynamically change the code generation optimization level (e.g., None) of a JIT in other to recompile a function with a new optimization level (e.g., Default)? Thank you. Best regards, Nurudeen.

I think this has to do with how the pass manager is populated when we give -O3 vs when we give particular pass names. Some passes have multiple createXYZPass() methods that accept arguments too. These methods call non-default pass constructors, which in turn cause the passes to behave in a different manner. eg: Pass *llvm::createLICMPass() { return new LegacyLICMPass(); } Pass

Hi, I'm a PhD student doing phase ordering as part of my PhD topic and I would like to ask some questions about LLVM. Executing the following command to see what passes does OPT execute when targeting a SPARC V8 processor: /opt/clang+llvm-3.7.1-x86_64-linux-gnu-ubuntu-15.10/bin/llvm-as < /dev/null | /opt/clang+llvm-3.7.1-x86_64-linux-gnu-ubuntu-15.10/bin/opt -O3 -march=sparc -mcpu=v8

If you pass -O0 to clang, most functions will be tagged with an optnone function attribute that will prevent opt and llc even if you pass -O3 to opt and llc. This is the mostly likely cause for the slow down in 2. You can disable the optnone function attribute behavior by passing "-Xclang -disable-O0-optnone" to clang ~Craig On Fri, Jan 5, 2018 at 1:19 PM, toddy wang via llvm-dev <

O0 didn't start applying optnone until r304127 in May 2017 which is after the 4.0 family was branched. So only 5.0, 6.0, and trunk have that behavior. Commit message copied below Author: Mehdi Amini <joker.eph at gmail.com> Date: Mon May 29 05:38:20 2017 +0000 IRGen: Add optnone attribute on function during O0 Amongst other, this will help LTO to correctly handle/honor

Craig, thanks a lot! I'm actually confused by clang optimization flags. If I run clang -help, it will show many optimizations (denoted as set A) and non-optimization options (denoted as set B). If I run llvm-as < /dev/null | opt -O0/1/2/3 -disable-output -debug-pass=Arguments, it also shows many optimization flags (denote as set C). There are many options in set C while not in set A,

I don't think "clang -help" prints options about optimizations. Clang itself doesn't have direct support for fine grained optimization control. Just the flag for levels -O0/-O1/-O2/-O3. This is intended to be simple and sufficient interface for most users who just want to compile their code. So I don't think there's a way to pass just -dse to clang. opt on the other hand

@Zhaopei, thanks for the clarification. @Craig and @Michael, for clang 4.0.1, -Xclang -disable-O0-optnone gives the following error message. From which version -disable-O0-optnone gets supported? [twang15 at c89 temp]$ clang++ -O0 -Xclang -disable-O0-optnone -Xclang -disable-llvm-passes -c -emit-llvm -o a.bc LULESH.cc error: unknown argument: '-disable-O0-optnone' [twang15 at c89

Hi, "SetC" options are LLVM cl::opt options, they are intended for LLVM developer and experimentations. If a settings is intended to be used as a public API, there is usually a programmatic way of setting it in LLVM. "SetA" is what clang as a C++ compiler exposes to the end-user. Internally clang will (most of the time) use one or multiple LLVM APIs to propagate a settings.

Within the LLVM pass manager infrastructure, suppose we have two transformation passes, pass A makes some improvements, then pass B does likewise, but this creates opportunities for pass A to create further improvements (e.g. suppose B was function inlining) so it's desirable to run A again. How does the LLVM pass manager currently deal with this? -------------- next part -------------- An

What I am trying is to compile a program with different sets of optimization flags. If there is no fine-grained control over clang optimization flags, it would be impossible to achieve what I intend. Although there is fine-grained control via opt, for a large-scale projects, clang-opt-llc pipeline may not be a drop-in solution. On Fri, Jan 5, 2018 at 10:00 PM, Craig Topper <craig.topper at