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

[Sungjin Kim]

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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