[LLVMdev] adding comment

[Daniel Sanders]

I tried out CommentFlag and it looks ideal for this purpose. The attached patch adds a FastISel flag and prints it in the AsmPrinter and the IR dump. You can then call MachineInstr::setAsmPrinterFlag(MachineInstr::FastISel) to set the flag.

Some passes seem to be stripping the comment flags though. The one I noticed is the pseudo-instruction expansion pass:
	# *** IR Dump After Machine Copy Propagation Pass ***:
	# Machine code for function retfloat: Post SSA

	BB#0: derived from LLVM BB %entry
		RetRA; comment-flags: FastISel

	# End machine code for function retfloat.

	# *** IR Dump After Post-RA pseudo instruction expansion pass ***:
	# Machine code for function retfloat: Post SSA

	BB#0: derived from LLVM BB %entry
		RET %RA

	# End machine code for function retfloat.

> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
> On Behalf Of Reed Kotler
> Sent: 17 April 2014 16:30
> To: LLVMdev at cs.uiuc.edu
> Subject: Re: [LLVMdev] adding comment
> 
> Maybe adding it to CommentFlag would be slightly better.
> 
> On 04/17/2014 02:23 AM, Daniel Sanders wrote:
> > Would adding a flag to MachineInstr::MIFlag do the trick? I'm thinking that
> fast isel could ensure that a flag (e.g. MIFlag::FastISel) is added to the
> instructions it creates, then the instruction printer could optionally emit a
> comment for instructions that have this flag.
> >
> >> -----Original Message-----
> >> From: llvmdev-bounces at cs.uiuc.edu
> >> [mailto:llvmdev-bounces at cs.uiuc.edu]
> >> On Behalf Of Reed Kotler
> >> Sent: 16 April 2014 22:17
> >> To: LLVMdev at cs.uiuc.edu
> >> Subject: Re: [LLVMdev] adding comment
> >>
> >> On 04/16/2014 02:06 PM, reed kotler wrote:
> >>> Is there a simple way to add a comment in the machine instructions
> >>> of a basic block?
> >>>
> >>> Ideally something that can be used with machine instruction builder.
> >>>
> >>> Tia.
> >>>
> >>> Reed
> >>
> >> In this case, I am working on the fast instruction selector for mips.
> >>
> >> I want to be able to tag instructions or regions of instructions that
> >> are emitted by the fast instruction selector as opposed to the normal
> >> mechanism.
> >>
> >> In fast instruction selector can always report that it cannot emit
> >> instructions for some construct and then that part falls on the
> >> normal mechanism; though in some cases the actual machine instructions
> emitted would be the same.
> >>
> >> So I want to be able to look for some kind of tag in the make check tests.
> >>
> >> Tia.
> >>
> >> Reed
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
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