New to LLVM. Need help generating assembly

Hi,
I’m new to LLVM and need some help. I defined an instruction to increment the stack pointer by ‘amount’ (i.e. sp = sp + amount). During assembly generation, the string that gets emitted is “ADS $SP” rather than “ADS 10”, for example, if I want to increment it by 10.

Can somebody show me what I’m doing wrong?
Thanks.

def ADS: F_J<0b100001,(outs),(ins i32imm:$amount),“ADS $amount”,[(set SP, (add SP, i32imm:$amount))] > {

bits<10> amount;

let Inst{9-0} = amount;

let isReMaterializable = 1;

let mayLoad = 0;

let mayStore = 0;

let Defs = [SP];

let Uses = [SP];

}

Hi,
I'm new to LLVM and need some help. I defined an instruction to increment the stack pointer by 'amount' (i.e. sp = sp + amount). During assembly generation, the string that gets emitted is "ADS $SP" rather than "ADS 10", for example, if I want to increment it by 10.

Can somebody show me what I'm doing wrong?
Thanks.

def ADS: F_J<0b100001,(outs),(ins i32imm:$amount),"ADS $amount",[(set SP, (add SP, i32imm:$amount))] > {

        bits<10> amount;

        let Inst{9-0} = amount;
        let isReMaterializable = 1;
        let mayLoad = 0;
        let mayStore = 0;
        let Defs = [SP];
        let Uses = [SP];
}

What does the MCInst dump of this instruction look like? Have you looked
at YourTargetGenAsmWriter.inc to see which print methods are being called
for this instruction?

-Tom

Hi,
I’m new to LLVM and need some help. I defined an instruction to increment the stack pointer by ‘amount’ (i.e. sp = sp + amount). During assembly generation, the string that gets emitted is “ADS $SP” rather than “ADS 10”, for example, if I want to increment it by 10.

Can somebody show me what I’m doing wrong?
Thanks.

def ADS: F_J<0b100001,(outs),(ins i32imm:$amount),“ADS $amount”,[(set SP, (add SP, i32imm:$amount))] > {

bits<10> amount;

let Inst{9-0} = amount;
let isReMaterializable = 1;
let mayLoad = 0;
let mayStore = 0;
let Defs = [SP];
let Uses = [SP];
}

What does the MCInst dump of this instruction look like? Have you looked
at YourTargetGenAsmWriter.inc to see which print methods are being called
for this instruction?

-Tom

It’s also worth checking the output of the compiler with the -print-after-all option to see if your instruction is present in the last IR dump. It’s possible that another instruction is being selected instead of this one.

Swapping the order of SP and $amount in the pattern did not work.

I checked the output of the compiler with the -print-after-all option and the instruction is present in the last IR dump.

I noticed that in GenAsmWriter.inc, there is this line of code in the case of my ADS instruction

printOperand(MI, 0, O);

If I manually change it to printOperand(MI, 1, O);, then it fixes the problem.

How can I make tablegen generate a 1 as the 2nd argument of printOperand for this specific instruction?

Swapping the order of SP and $amount in the pattern did not work.
I checked the output of the compiler with the -print-after-all option and the instruction is present in the last IR dump.

I noticed that in GenAsmWriter.inc, there is this line of code in the case of my ADS instruction
printOperand(MI, 0, O);

If I manually change it to printOperand(MI, 1, O);, then it fixes the problem.

How can I make tablegen generate a 1 as the 2nd argument of printOperand for this specific instruction?

SP is supposed to be an implicit argument, so printOperand(MI, 0, 0) is correct.
Can you find out where SP is added as an explicit operand? Does this happen
after ISEL or some time later?

-Tom

Swapping the order of SP and $amount in the pattern did not work.

The tablegen internals will have generated patterns for both ways around because add is commutative and then removed the one with the immediate on the left to because it knows that DAGISel ensures the immediate is on the right.

I checked the output of the compiler with the -print-after-all option and the instruction is present in the last IR dump.

Ok, in that case it’s being selected but isn’t printing correctly. Could you copy output line for that instruction here? It’s sounding like the operand list in your MCInst doesn’t agree with the tablegen definition.