[LLVMdev] load/store in IR without stack/heap

[Kangkook Jee]

did you try mem2reg optimization pass?
this transform load/store operations to cheaper operations with virtual registers. 

On Jul 5, 2011, at 2:12 PM, Sungjin Kim wrote:

> Hi all,
> 
> Can anyone give an idea to solve my problem? I'm implementing backend part 
> using LLVM for my research architecture. The main issue is that this architecture
> cannot use stack/heap. So, all the value should be stored in the register.
> Given that architecture, load/store instruction in IR uses virtual register to load/
> store the value. For example:
> C source code is:
> 
> if(...) {
>     a = 1;
> } 
> else {
>     a = 0;
> }
> c = a;
> 
> It's IR from the front-end is:
> ...
> ;<label>:3
> store i16 1, i16 *a, align 2
> br label %5
> ;<label>:4
> store i16 0, i16 *a, align 2
> br label %5
> 
> ;<label>:5
> %6 = load i16 *a, align 2
> store i16 %6, i16 c
> 
> I used getCopyToReg in SelectionDAG for store instruction to store value, and getCopyFromReg 
> for load instruction. So, storage values in block '<label>:3' and '<label>:4' are stored in VR0 and 
> VR1 respectively. However, load instruction in block '<label>:5' cannot choose which register 
> should be read.
> Can anybody give an idea to overcome such a case?
> 
> Thanks.
> 
> Jin _______________________________________________
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