[LLVMdev] Custom Opcodes versus built-in opcodes

[Villmow, Micah]

________________________________

From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
On Behalf Of Chris Lattner
Sent: Friday, September 19, 2008 11:47 AM
To: LLVM Developers Mailing List
Subject: Re: [LLVMdev] Custom Opcodes versus built-in opcodes

 

On Sep 19, 2008, at 11:35 AM, Villmow, Micah wrote:

	

	Make sure to use DAG.getTargetNode() with custom opcodes.
"target" nodes are encoded with an implicit delta added to their enum
value.

	 

	Is this documented anywhere that getTargetNode is the preferred
method to use in a Custom Lowering function? Even the other backends use
getNode in their lowering functions with custom opcodes.

	This is from SparcISelLowering.cpp

	CompareFlag = DAG.getNode(SPISD::CMPFCC, MVT::Flag, LHS, RHS);

	    if (SPCC == ~0U) SPCC = FPCondCCodeToFCC(CC);

	    Opc = SPISD::BRFCC;

	  }

	  return DAG.getNode(Opc, MVT::Other, Chain, Dest,

	                     DAG.getConstant(SPCC, MVT::i32),
CompareFlag);

 

Actually, I'm wrong, sorry about that.  It looks like the encoding is in
the definition of the enum:

 

   enum {

      FIRST_NUMBER = ISD::BUILTIN_OP_END+SP::INSTRUCTION_LIST_END,

      CMPICC,      // Compare two GPR operands, set icc.

      CMPFCC,      // Compare two FP operands, set fcc.

      BRICC,       // Branch to dest on icc condition

      BRFCC,       // Branch to dest on fcc condition

...

 

Are your "targetISD" enums properly defined with the offset?

 

 

getTargetNode is required when passing in MachineInstr opcode numbers at
isel time.

 

Ahhh! Thanks.

 

Micah

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20080919/482d7a39/attachment.html>