similar to: [LLVMdev] How to assign undef value to a variable

Simply create an undef constant value and add a store instruction to store the undef value into the memory allocated by the alloca. I believe there is an llvm::Undef class. Check doxygen docs for details. -----Original Message----- From: Chayan Sarkar <chayan.ju at gmail.com> Sent: Sunday, June 27, 2010 12:05 PM To: llvmdev at cs.uiuc.edu <llvmdev at cs.uiuc.edu>; chayan.ju at

Hi Chayan, > Can any one tell me how to assign 'undef' to variable? I want to > assign each variable an undef, immediately after the alloca > instruction. by default an AllocaInst starts off with the memory implicitly set to undef. Ciao, Duncan.

Hi, I could not figure out, how to declare a Pass*. Can anyone give me an example, how to use SplitEdge() function ? Please help me out. Regards, Chayan On Tue, Jul 20, 2010 at 10:12 AM, Chayan Sarkar <chayan.ju at gmail.com> wrote: > Hi All, > > Still I could not figure out how to use Pass* while calling > SplitEdge() function. Can anyone provide me some example? > >

But, the mem2reg pass removes all load store instructions. It replaces all variables by their if possible (kind of constant propagation). I have generated the bitcode of the source program and the applied the mem2reg pass and obviously not getting desired thing. What I want is convert it into SSA form without replacing any variable by their constant value. Please elaborate on your point. Also,

Hi All, Still I could not figure out how to use Pass* while calling SplitEdge() function. Can anyone provide me some example? Regards, Chayan On Sun, Jul 18, 2010 at 11:49 PM, Nick Lewycky <nicholas at mxc.ca> wrote: > Chayan Sarkar wrote: >> >> Hi, >> >> I have tried to use SplitEdge function, but failed. Actually the third >> parameter is a variable of

Hi Jeffrey, Actually I am trying to implement "E-path PRE" which is based on non-algebric equivallence. So, the variable names need to be preserved. You said that I need to insert these to preserve variable %a.0 = bitcast i32 2 to i32 So, these need to be inserted before the mem2reg pass or within the pass. In first case, how to call an inbuilt pass after doing some analysis from my

E-path PRE requires the program in SSA form like SSAPRE algorithm. Then it finds the eliminatable path (e-path) for an expression and converts partially redundant to fully redundant and removes redundancy Chayan On Mon, Jun 7, 2010 at 1:58 PM, Eli Friedman <eli.friedman at gmail.com> wrote: > On Sun, Jun 6, 2010 at 8:56 PM, Chayan Sarkar <chayan.ju at gmail.com> wrote: >> Hi

There is no existing pass to do this in LLVM, mostly because it wouldn't be useful for optimizing programs. From your input, mem2reg produces: define i32 @myfunc(i32 %x, i32 %y) nounwind { entry: %cmp = icmp sgt i32 %x, %y ; <i1> [#uses=1] br i1 %cmp, label %if.then, label %if.else if.then: ; preds = %entry %add = add

On Sun, Jun 6, 2010 at 8:56 PM, Chayan Sarkar <chayan.ju at gmail.com> wrote: > Hi Jeffrey, > > Actually I am trying to implement "E-path PRE" which is based on > non-algebric equivallence. So, the  variable names need to be > preserved. Then why do you want to run mem2reg before your optimization in the first place? -Eli

You can use STOREs and LOADs on memory and then use mem2reg pass. 2010/6/1 Chayan Sarkar <chayan.ju at gmail.com>: > Hi, > > Can anyone tell me, whether it is possible to convert a program into > SSA form without considering algebric equivalence ? > > regards, > Chayan > _______________________________________________ > LLVM Developers mailing list > LLVMdev at

Suppose my Input function is like : myfunc(int x,int y){ int a=2, b=3,c=5; if(x>y) { c=a+b; a=6; } else { c=a*b; b=4; } a=c+a; c=a+b; } and the output should be : myfunc(int x,int y){ int a.0=2, b.0=3,c.0=5; if(x>y) { c.1=a.0+b.0; a.1=6; } else { c.2=a.0*b.0; b.1=4; }

Hi, Can anyone tell me, whether it is possible to convert a program into SSA form without considering algebric equivalence ? regards, Chayan

On Sat, Jun 5, 2010 at 2:03 AM, Chayan Sarkar <chayan.ju at gmail.com> wrote: > But, the mem2reg pass removes all load store instructions. It replaces > all variables by their if possible (kind of constant propagation). I > have generated the bitcode of the source program and the applied the > mem2reg pass and obviously not getting desired thing. > > What I want is convert

Hi, I am trying to write a small pass. In my pass, I have inserted some instruction and used that in another. But, during OPT it is showing "Instruction does not dominate all uses" like following - %b.1 = bitcast i32 4 to i32 ; <i32> [#uses=8] %11 = add i32 %a.1, %b.1 ; <i32> [#uses=1]Instruction does not dominate all uses! Any

Chayan Sarkar wrote: > Hi, > > I have tried to use SplitEdge function, but failed. Actually the third > parameter is a variable of type Pass and it need to be non-null. But I > could not figure out how to use it. Please help me out. The only reason it needs a non-NULL Pass* is to call llvm::SplitBlock which uses P->getAnalysisIfAvailable unconditionally. Feel free to wrap

Hi, I have tried to use SplitEdge function, but failed. Actually the third parameter is a variable of type Pass and it need to be non-null. But I could not figure out how to use it. Please help me out. Regards, Chayan On Sat, Jul 17, 2010 at 10:16 PM, Nick Lewycky <nicholas at mxc.ca> wrote: > Chayan Sarkar wrote: >> >> Hi all, >> >> Suppose in a CFG bb1 has two

Hi, Lately we have come to realize how undef makes our life complicated.. Therefore in this email we propose to change the behavior of a few instruction to yield poison instead of undef in error cases. This follows the suggestion of Eli in https://reviews.llvm.org/D33654. Why is undef so bad? - I believe it's not possible to make newgvn correct with undef. See for example the discussion

Hi, Can anyone tell me how to erase an instruction, (specially a load/store instruction) ? If I use Instr->eraseFromParent(), I get following error. Note the instruction does not have any use. opt: /home/chayan/llvm/llvm-2.6/include/llvm/ADT/ilist.h:218: llvm::ilist_iterator<NodeTy>& llvm::ilist_iterator<NodeTy>::operator++() [with NodeTy = llvm::Instruction]: Assertion

On Fri, Dec 9, 2016 at 10:30 AM, Friedman, Eli <efriedma at codeaurora.org> wrote: > Mmm... maybe. The part I really don't like is the implied store: there > are a lot of transformations which specifically reason about store > instructions, and they would all need to be fixed to specifically deal with > "alloca with an argument" so it doesn't block

Hi Soham, You're right that in LLVM IR arithmetic (with the current definition of `undef`) is not distributive. You can't replace `A * (B + C)` with `A * B + A * C` in general, since (exactly as you said) for A = `undef`, B = `1`, C = `-1` the former always computes `0` while the latter computes `undef`. This is fundamentally because replacing `A * (B + C)` with `A * B + A * C`