[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 10:49 AM
To: LLVM Developers Mailing List
Subject: Re: [LLVMdev] Custom Opcodes versus built-in opcodes

 

 

On Sep 18, 2008, at 4:04 PM, Villmow, Micah wrote:





I am using lowering instructions and using custom opcodes that I can
more easily directly map to my backend. These opcodes are then used to
emit a custom set of instructions into the MachineBasicBlock. I've been
able to get one to work correctly, however, I've ran into an issue where
my second one is being confused as a FRAMEADDR opcode instead of my
opcode.

 

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);

 

Micah

 

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