[llvm-dev] Bundling MachineInstr instructions before register allocation seems to always give errors
Alex Susu via llvm-dev
llvm-dev at lists.llvm.org
Thu Feb 23 06:45:05 PST 2017
I am having difficulties to bundle MachineInstr instructions, before register
More exactly, I registered a simple pass in addPreRegAlloc() that is trying to create
I see that it is written at http://llvm.org/docs/CodeGenerator.html#machineinstr-bundles:
<<Packing / bundling of MachineInstr’s should be done as part of the register
More specifically, the pass which determines what MIs should be bundled
together must be done after code generator exits SSA form (i.e.
after two-address pass, PHI elimination, and copy coalescing).
Bundles should only be finalized (i.e. adding BUNDLE MIs and input and
output register MachineOperands) after virtual registers have been
rewritten into physical registers.
This requirement eliminates the need to add virtual register operands
to BUNDLE instructions which would effectively double the virtual
register def and use lists.>>
I presume this is the reason why I'm getting always errors after creating bundles in
the pass registered in addPreRegAlloc().
More exactly, my pass seems to be invoked before the "Eliminate PHI nodes for
register allocation" pass.
If however, there is a simple possibility to bundle MachineInstr before RA, please
let me know.
PS: Is there a possibility to bundle MachineInstr instructions before RA and use
llvm::finalizeBundle() on these bundles in a pass invoked after RA?
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