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So why does the code produced in the last exercise contain the labels .LBB0_2 and .LBB0_3 but no .LBB0_1? Well that is because I have added a code generation pass that deletes useless jumps like: JNC .LBB0_1 .LBB0_1: Code snippets: void HP41MCODEPassConfig::addPreEmitPass() { addPass(new RemoveUselessJMP()); } … bool RemoveUselessJMP::runOnMachineBasicBlock( MachineBasicBlock &MBB, MachineBasicBlock &MBBN) { bool … Continue reading »

It is time to bring in some conditionals. Adding an “if” to our friend foo(): int foo() { int retval1 = 0x0AB; int retval2 = 0; if (retval2) return retval2; return retval1; } We need to implement instructions for both conditional and unconditional branches (i.e jumps). An unconditional branch is just like this (assuming no … Continue reading »

Let us add some local variables: int foo() { int retval = 0x0AB; int dummy = 0; return retval; } This requires adding some information about accessing memory. I will just postulate that I have memory available from address 1 growing upwards. As anyone that really knows the HP-41 understands, this is a very bad … Continue reading »

How about calling another function: int foo() { return 0xFF; } int bar() { return foo(); } Code snippets: … def CC_HP41MCODE : CallingConv<[]>; … def SDT_HP41MCODENCXQ : SDTypeProfile<0, -1, [SDTCisVT<0, iPTR>]>; def HP41MCODENCXQ : SDNode<“HP41MCODEISD::NCXQ”, SDT_HP41MCODENCXQ, [SDNPHasChain, SDNPOptInGlue, SDNPOutGlue, SDNPVariadic]>; … def calltarget : Operand; … let isCall=1 in { def NCXQ : HP41MCODEInst<0x001, … Continue reading »

This is sort of the opposite of the Quantum Teleportation we have covered earlier. Here you use quantum bits to transfer classical bits: We have all the building blocks we need from the previous episode, so let me just show you the additional code: #Alice bits a1=1 a2=1 print(“Alice bits:”,a1,a2) #Initialize inputs q=[[1],[0],[0],[0]] #Build circuit … Continue reading »

Let us return a larger constant: int foo() { return 0xFF; } For numbers up to 12 bits we can use the LDI S&X instruction. Some code snippets: def immSExt12 : PatLeaf<(imm), [{ return isInt<12>(N->getSExtValue()); }]>; def : Pat<(i32 immSExt12:$in), (LDI imm:$in)>; def LDI : HP41MCODEInst<0x130, (outs RC:$r), (ins i32imm:$sx), “LDI S&X HEX: $sx”, [(set … Continue reading »

A tiny addition to the empty function. Returning zero: int foo() { return 0; } Remember, we will not care about returning values to the calculator registers (at not least for now). We will only generate functions callable from MCODE. So as a convention we will choose to return values in the C register. So … Continue reading »