[cfe-dev] [LLVMdev] Clang flag to either print/omit nop instruction in llvm backend

[Daniel Sanders]

One possibility is adding the option to the backend instead and using '-mllvm –no_nop_optimise' on the clang command. This approach is good for options you don't intend end-users to use.

Just to check: The NOP's you're trying to eliminate aren't related to branch delay slots are they? The reason I ask is because removing those without putting another instruction in their place will change the behaviour of your code.

From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Ambuj Agrawal
Sent: 19 March 2015 15:45
To: llvmdev at cs.uiuc.edu; cfe-dev at cs.uiuc.edu
Subject: [LLVMdev] Clang flag to either print/omit nop instruction in llvm backend

I have created custom Clang flag -no_nop_optimise which can be passes with clang on command line.
I am planning to implement someting like:
when -no_nop_optimise flag is passed on the command line do not emit a nop instruction.
i.e. inside SelLowering class
if ( !OPT_no_nop_optimise)
{
      BuildMI(*BB, MI, DL, TII->get(Mips::NOP));
}

Any clues on how can I pass the flag to the LLVM backend from clang?

Thanks,
Ambuj
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