[LLVMdev] Eliminate SSA Virtual registers

[Jeremy Lakeman]

The reg2mem pass only eliminates phi nodes, using the stack to pass values
between basic blocks.
LLVM models a register based CPU, not a stack based one. All calculations
are assumed to be performed in registers with the arguments and results
loaded and stored from the stack.

What other constraints are you hoping to enforce on your flavour of IR?


On Sun, Feb 2, 2014 at 3:27 AM, <nizam at cse.iitm.ac.in> wrote:

> I mean to say didnt help. :)
>
> ------------------------------
> *From: *nizam at cse.iitm.ac.in
> *To: *"Benjamin Kramer" <benny.kra at gmail.com>
> *Cc: *"llvmdev" <llvmdev at cs.uiuc.edu>
> *Sent: *Saturday, February 1, 2014 9:53:55 PM
>
> *Subject: *Re: [LLVMdev] Eliminate SSA Virtual registers
>
>
> Hi Ben,
>
>
> That did help. I continue to notice the virtual register in the program. I
> use LLVM 3.4. The program i am looking  at  is a very simple one. Listed
> below
>
> int global_var;
> int *global_ptr;
>
> int32_t main(int32_t argc, char ** argv){
>    int p = 10;
>    int k = 20;
>    int *pp;
>    char *c_pp;
>
>    pp = &k;
>    global_ptr = pp;
>    pp = &p;
>    global_ptr = &global_var;
>    return 0;
> }
> BR/Nizam
>
>
>
> ------------------------------
> *From: *"Benjamin Kramer" <benny.kra at gmail.com>
> *To: *nizam at cse.iitm.ac.in
> *Cc: *"llvmdev" <llvmdev at cs.uiuc.edu>
> *Sent: *Saturday, February 1, 2014 9:57:00 PM
> *Subject: *Re: [LLVMdev] Eliminate SSA Virtual registers
>
>
> On 01.02.2014, at 16:47, nizam at cse.iitm.ac.in wrote:
>
> > Hi,
> >
> > is there a opt pass that replaces the SSA virtual registers to
> stack-variables? I want to eliminate the SSA virtual register from my IR.
> Kindly suggest
>
> Try the register to memory demotion pass. opt -reg2mem
>
> - Ben
>
>
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