similar to: How to prevent llvm's default optimization

Yes - this has been in InstCombine for a long time: https://github.com/llvm/llvm-project/blob/master/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp#L268 We could say that the canonicalization should be reversed, but that probably uncovers more missing optimizations. The code size concern is legitimate. For example on x86, gcc asm is 2 bytes smaller on this example:

Thanks. I have checked the hook DAGCombiner::isMulAddWithConstProfitable And I think the above condition is too aggressive. // If the add only has one use, this would be OK to do. if (AddNode.getNode()->hasOneUse()) return true; Shall we make it to if (AddNode.getNode()->hasOneUse() && TargetLowering.isCheaperCommuteAddMul(......)) return true; The virtual hook

The attached patch includes no test-case and isn't consistent with the rest of the file: - constants should be on the right hand side of comparisons - the braces around your single line 'if' aren't needed. On Sun, Sep 15, 2013 at 2:39 PM, James Courtier-Dutton < james.dutton at gmail.com> wrote: > I attach a patch that fixes this bug. Applies to llvm 3.4svn > >

Test case attached. It is not a test case that works within the llvm test-suite yet, but it does demonstrate the problem. I would like some advice on how to modify this test_case so that it can be added to the automated llvm test cases. On 15 September 2013 23:02, David Majnemer <david.majnemer at gmail.com> wrote: > The attached patch includes no test-case and isn't consistent

I attach a patch that fixes this bug. Applies to llvm 3.4svn Please commit it please. Kind Regards James On 13 September 2013 17:46, James Courtier-Dutton <james.dutton at gmail.com>wrote: > Hi, > > I am looking at the "LLVMOpInfoCallback GetOpInfo" callback. > > Example 1 GOOD: > 41 c6 84 24 16 04 00 00 0c : movb $12, 1046(%r12) > > Makes

On Mar 15, 2013 10:53 PM, "Óscar Fuentes" <ofv at wanadoo.es> wrote: > > James Courtier-Dutton <james.dutton at gmail.com> writes: > > > I think this is a very simple question, and it must just be missing something. > > > > I am looking for find out how to assign a constant integer value to > > the variable in llvm ir. > > > > The

On Mon, Oct 28, 2013 at 10:09 AM, James Courtier-Dutton <james.dutton at gmail.com> wrote: > My guess is that this is a missed optimization, but in real life, all > projects i have worked fix this in the C or C++ code using macros that > change what instructions are used based on target platform and its > endedness. One reason for writing code like this, i.e. explicitly spelling

On Mar 15, 2013, at 3:08 PM, James Courtier-Dutton <james.dutton at gmail.com> wrote: > Hi, > > I think this is a very simple question, and it must just be missing something. > > I am looking for find out how to assign a constant integer value to > the variable in llvm ir. > > The following returns 12, and %var2 = 12. > ; ModuleID = 't.c' > target

James Courtier-Dutton <james.dutton at gmail.com> writes: > I think this is a very simple question, and it must just be missing something. > > I am looking for find out how to assign a constant integer value to > the variable in llvm ir. > > The following returns 12, and %var2 = 12. > ; ModuleID = 't.c' > target datalayout = >

Look at the __builtin_addc* builtins in clang. I am currently working on an optimization which transforms said intrinsics into chains of ADCs/SBBs. Michael On Jun 28, 2013, at 5:51 AM, James Courtier-Dutton <james.dutton at gmail.com> wrote: > Hi, > > I have the x86 SBB instruction. how should I represent this in LLVM > IR. (as part of a decompiler from binary to LLVM IR)

----- Original Message ----- > On Mon, Oct 28, 2013 at 10:09 AM, James Courtier-Dutton > <james.dutton at gmail.com> wrote: > > My guess is that this is a missed optimization, but in real life, > > all > > projects i have worked fix this in the C or C++ code using macros > > that > > change what instructions are used based on target platform and its >

----- Original Message ----- > From: "Anton Korobeynikov" <anton at korobeynikov.info> > To: "James Courtier-Dutton" <james.dutton at gmail.com> > Cc: "Hal Finkel" <hfinkel at anl.gov>, "Bill Wendling" <isanbard at gmail.com>, "LLVM Developers Mailing List" > <llvmdev at cs.uiuc.edu> > Sent: Saturday,

On Sun, Apr 16, 2017 at 2:34 AM James Courtier-Dutton via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Hi, > > Did this work ever get done? There was a long thread about it back in 2015. > > I wish to use IRBuilder. > Is there any documentation? > How do I use the singular pointer type in GEP, LOAD, STORE instructions? > Sorry, no, the work is not complete - for

I wrote up this optimization as an LLVM IR pass last month, actually: https://code.google.com/p/foster/source/browse/compiler/llvm/passes/BitcastLoadRecognizer.cpp It recognizes trees of `or' operations where the leaves are (buf[v+c] << c * sizeof(buf[0])). There are a few improvements needed to make it fit for general consumption; it assumes (without checking) that it's targeting

> -----Original Message----- > On Behalf Of James Courtier-Dutton > To: John Criswell > > On 7 May 2012 16:31, John Criswell <criswell at illinois.edu> wrote: > > On 5/7/12 5:47 AM, James Courtier-Dutton wrote: > >> > >> Hi, > >> > >> I am writing a decompiler. I was wondering if some of LLVM could be > >> used for a

James Courtier-Dutton <james.dutton at gmail.com> writes: > I am looking to decompile x86 ASM to LLVM IR. > The original C is this: > int test61 ( unsigned value ) { > int ret; > if (value < 1) > ret = 0x40; > else > ret = 0x61; > return ret; > } > > It compiles with GCC -O2 to (rather

On Mon, 6 May 2019 at 10:13, James Courtier-Dutton via llvm-dev <llvm-dev at lists.llvm.org> wrote: > Although the above is mentioning bytes, looking at the "/ 8" and "& 0x7" makes it look like the author meant octets and not bytes. > Bytes can be any size of bits. I don't think you'll have much luck trying to make that stick for a general audience,

Thanks for your replies. Working on the lfort compiler would certainly be an interesting project for me for this GSoC. I have studied lfort repository and commits, and I see that it has a lot of stuff for C/C++, am I correct that this is a fork of Clang? If this is correct, I wonder why this approach was chosen instead of starting out from scratch - is it because Clang already has a lot of code

On 7 May 2012 16:31, John Criswell <criswell at illinois.edu> wrote: > On 5/7/12 5:47 AM, James Courtier-Dutton wrote: >> >> Hi, >> >> I am writing a decompiler. I was wondering if some of LLVM could be >> used for a decompiler. >> There are several stages in the decompiler process. >> 1) Take binary and create a higher level representation of it.

On 8 May 2018 at 16:34, James Courtier-Dutton via llvm-dev <llvm-dev at lists.llvm.org> wrote: > Has something changed? > So, it seams that LLVM do not participate in Outreachy. Last email from Tanya was looking for folks to participate, there was no update that it wouldn't happen. Maybe this is a new development? Anyway, I think if the foundation considers this again, there