llvm dev - Jul 2012 - [LLVMdev] (no subject)

I'm working on translating llvm's optimized intermediate code to another
compiler's intermediate code, and I'm working on the PHI instruction.

Here's an example phi instruction to help explain what I'm trying to do:
%inc25 = phi i32 [ 1, %entry ], [ %inc, %for.body ]

What I would want to do here is allocate some memory memory (i'm trying to
use %phi1 = alloca  i32, allign 4 ). Then, I want to go to the %entry block
and say "store i32  1, i32* %phi1", and in the %for.body I want to add
"store i32  1, i32* %phi1".

So first, I'm iterating through my function and basicblock:
    int phi = 0;
    Function::iterator func_bblock_itr = func->begin();
    for(; func_bblock_itr != func->end(); ++func_bblock_itr)
    {
        BasicBlock::iterator bblock_inst_itr = func_bblock_itr->begin();
        for(; bblock_inst_itr != func_bblock_itr->end(); ++bblock_inst_itr)
        {
Then, I look for PHI instructions:
            if(bblock_inst_itr->getOpcode() == Instruction::PHI) {
If I find one, I allocate space:
                string name = "phi";
                name.insert(3,to_string(phi));
                Twine tname= Twine(name);
                AllocaInst alloca
AllocaInst(bblock_inst_itr->getOperand(0)->getType(),tname,func_bblock_itr->begin());
and then i go through the operands one by one to find where to put store
instructions:
                for(unsigned int i = 0; i <
bblock_inst_itr->getNumOperands();i++) {
                    Value *v = bblock_inst_itr->getOperand(i);
Here's where I don't know what to do: I want to create a store
instruction
in that place
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If you want to eliminate phi instructions, you can try to just use the
reg2mem pass.  This will do what you're trying to accomplish here.

On Wed, Jul 18, 2012 at 5:04 PM, ryan baird <ryanrbaird at gmail.com>
wrote:
> I'm working on translating llvm's optimized intermediate code to
another
> compiler's intermediate code, and I'm working on the PHI
instruction.
>
> Here's an example phi instruction to help explain what I'm trying
to do:
> %inc25 = phi i32 [ 1, %entry ], [ %inc, %for.body ]
>
> What I would want to do here is allocate some memory memory (i'm trying
to
> use %phi1 = alloca  i32, allign 4 ). Then, I want to go to the %entry block
> and say "store i32  1, i32* %phi1", and in the %for.body I want
to add
> "store i32  1, i32* %phi1".
>
> So first, I'm iterating through my function and basicblock:
>     int phi = 0;
>     Function::iterator func_bblock_itr = func->begin();
>     for(; func_bblock_itr != func->end(); ++func_bblock_itr)
>     {
>         BasicBlock::iterator bblock_inst_itr = func_bblock_itr->begin();
>         for(; bblock_inst_itr != func_bblock_itr->end();
++bblock_inst_itr)
>         {
> Then, I look for PHI instructions:
>             if(bblock_inst_itr->getOpcode() == Instruction::PHI) {
> If I find one, I allocate space:
>                 string name = "phi";
>                 name.insert(3,to_string(phi));
>                 Twine tname= Twine(name);
>                 AllocaInst alloca >
AllocaInst(bblock_inst_itr->getOperand(0)->getType(),tname,func_bblock_itr->begin());
> and then i go through the operands one by one to find where to put store
> instructions:
>                 for(unsigned int i = 0; i <
> bblock_inst_itr->getNumOperands();i++) {
>                     Value *v = bblock_inst_itr->getOperand(i);
> Here's where I don't know what to do: I want to create a store
instruction
> in that place
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>

-- 

Thanks,

Justin Holewinski
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