[LLVMdev] Pattern matching questions

[Scott Michel]

Chris Lattner wrote:
>>It is possible to write multi-instruction pattern, e.g.
>>X86InstrSSE.td line 1911. But how are you defining HI16 and LO16?
>>Sounds like you want to define them as SDNodeXform that returns upper
>>and lower 16 bits respectively. Take a look at PSxLDQ_imm in
>>X86InstrSSE.td as an example.
> 
> 
> Another good example is the PPC backend, which has the exact same issue 
> for integer constants.

Actually, for SPU, not quite the same:

def ILHU : RI16Form<0b010000010, (ops GPRC:$rT, u16imm:$val),
                    "ilhu $rT, $val", LoadNOP,
                    [(set GPRC:$rT, immZExt16:$val)]>;

def IOHL : RI16Form<0b100000110, (ops GPRC:$rT, u16imm:$val),
                    "iohl $rT, $val", LoadNOP,
                    [(set GPRC:$rT, immZExt16:$val)]>;

Thus, you can't really do as the PPC does, viz:

    (ORI (LIS (HI16 imm:$imm)), (LO16 imm:$imm))

vs.

    (IOHL (ILHU (HI16 imm:$imm)), (LO16 imm:$imm))

because there's only one operand to IOHL. PPC ORI is a two operand, one
result instruction. (I'm sure I'm bashing the vernacular badly.) My
question is how to link IOHL and ILHU together. Sequentially.

>>>- The return instruction for Cell SPU is "bi $lr". How do I jam that
>>>  into the instruction info w/o tblgen bitching up a storm about the
>>>  "$" or the extra "bi" operands?
>>
>>I am not sure. Does "bi \$lr" works? Or "bi $$lr"? Or even something
>>like
>>!strconcat("bi ", !strconcat("$", "lr")).
> 
> 
> Yep, $$ should work.

It doesn't. Here's the pattern:

let isTerminator = 1, isBarrier = 1, noResults = 1 in {
  let isReturn = 1 in {
    def RET: BRForm<0b00010101100, (ops),
                        "bi $$lr",
                        BranchResolv,
                        [(retflag)]>;
  }
}

Output from make:

llvm[0]: Building SPU.td code emitter with tblgen
tblgen: /work/scottm/llvm/utils/TableGen/CodeGenInstruction.h:118:
std::pair<unsigned int, unsigned int>
llvm::CodeGenInstruction::getSubOperandNumber(unsigned int) const:
Assertion `i < OperandList.size() && "Invalid flat operand #"' failed.
make: ***
[/work/scottm/llvm/obj/i686-unknown-linux-gnu/lib/Target/IBMCellSPU/Debug/SPUGenCodeEmitter.inc.tmp]
Aborted

Whiskey Tango... Foxtrot?