[llvm-dev] Inserting MachineInstr's

[Chris.Dewhurst via llvm-dev]

Hi,

I have a task to complete and I'm getting stuck. I can't find anything comparable in the documentation. The shortest explanation I can give is as follows: I need to use double-precision floating point values for floating-point multiplies. I'll not go into why: That would take the discussion away from the essential problem. E.g.

  Replace:


  fmuls %f20,%f21,%f8

  with the sequence:


  fstod %f20,%f0

  fstod %f21,%f2

  fmuld %f0,%f2,%f8

This is for a Sparc derived back-end and I'm already at the MachineInstr phase. The essential code I have now is as follows, but it doesn't work. I've had much larger pieces of code, but I believe my mistake lies somewhere in here. I'm not sure if I'm heading down the right path with this. Please, any help would be appreciated - or any reference to an example, even better.

[code is iterating through the MachineBasicBlock - this code is pretty straightforward and you can probably guess what's in it]
    if (Opcode == SP::FMULS)
      {
        MachineOperand& MO = MI.getOperand(0);
        DebugLoc DL = MBBI->getDebugLoc();
        BuildMI(MBB, MBBI, DL, TII.get(SP::FSTOD), MO.getReg());
           [ Then we'd do the second fstod and the fmuld, but I've not included this because the basic problem of generating the MachineInstr has happened already for this first MachineInstr]
        MI.eraseFromParent();
      }

Chris Dewhurst,
University of Limerick, Ireland
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