[llvm-dev] how to prevent LLVM back-end from reordering instructions at instruction scheduling?

[Wei Ding via llvm-dev]

Hello,

I have a LLVM backend question regarding how to prevent compiler from
reordering instructions. For example, I have the following instructions.
Z_instruction is the one which I want to insert.


// instruction order which I am looking for
/////////////////////////////////////////
A_instruction
B_instruction

*Z_instruction*

C_instruction
D_instruction
E_instruction
F_instruction

*Z_instruction*

G_instruction
F_instruction


==================================================

But I found compiler reordered those instructions like the following. How
could I prevent compiler from moving *A_instruction* and *B_instruction*
after the first *Z_instruction*? Any recommendations and suggestion are
greatly appreciated here!!!

*Z_instruction*

A_instruction
B_instruction

C_instruction
D_instruction
E_instruction
F_instruction

*Z_instruction*

G_instruction
F_instruction

BTW, I have define input/output chain for : *C_instruction, D_instruction,
E_instruction, F_instruction and Z_instruction*

Thank you so much!

-- 
Wei Ding
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