Code generation issues in compiler design

#Code generation issues in compiler design generator

But where standard functions cannot be inlined, your code generator can always write out the function implementation in the target language.The code generator is a good place to inline some standard functions.While not shown in the examples above, character sets may very well be different between the two languages keep that in mind.ItРІР‚в„ўs best to decorate the ids in the target language with uniquely identifying suffixes, because you never know whether scope rules are the same.When writing out high-level code, it is fine to over-parenthesize: you should probably not assume your associativities and precedences and arities and fixities are the same as those of your target language.Each nodeРІР‚в„ўs generate method invokes the generate method of its sub nodes.You write a generate method for each AST node.What did you notice from browsing these examples? A few tips and tricks, right? Things like: Each start with a decorated AST (thereРІР‚в„ўs pretty much no need to use an IR if you are targeting a high-level language): Start by browsing code of simple examples. JavaScript makes a great target language? Why? ItРІР‚в„ўs got first-class functions and async support, and that Node.js thing runs on that awesome V8. Should we stick in line number information so a debugger can take over if our program is stopped intentionally (or crashes)?.Mov x_2, rax Redundant if x not used again Should we generate awesome code on the fly? Or let a separate optimizing pass clean up after our generator? Or not optimize at all? For example, naive code generation can lead to not so great code:.Absolute machine language: youРІР‚в„ўve resolved all the memory locations in other words you spent a lot of time doing what assemblers and linkers would do for you already.

Relocatable machine language: youРІР‚в„ўve done a lot of assembly that the assembler would have done for you (resolving symbols), but at least you will let the linker do the rest.Is it a RISC or CISC processor or some kind of novel architecture like a dataflow processor or somthing with hundreds of cores? What are the relative instruction speeds? How are its addressing modes? Does it have out-of-order instruction? Any cool idioms? Assembly language: Because itРІР‚в„ўs so fulfilling to learn about machine architecture, especially pipelines, caches, and of course, registers! You need to know your machine.YouРІР‚в„ўll get a great feeling of accomplishment. Learning about a VM and its instruction set is a great experience.

Targeting a virtual machine is a ton of fun.

Executable virtual machine code, such as for the JVM or BEAM.

An intermediate representation like LLVM, that has backends for dozens of architectures.

But then you can let the C compiler take over to do the rest. If the target high-level language has a good compiler already, this is a great strategy. There is no one target of a code generator. There is no one way to do code generation.

The quality of the generated code can be determined by its speed and size.Exercise: The last two goals are seemingly in conflict.

When you consider the efficiency of target machine then the instruction speed and machine idioms are important factors.

Nature of instruction set of the target machine should be complete and uniform.

Local variables are stack allocation in the activation record while global variables are in static area.

Mapping name in the source program to address of data is co-operating done by the front end and code generator.

During code generation process the symbol table entries have to be mapped to actual p addresses and levels have to be mapped to instruction address.

The output can be:Р”Р„) Assembly language: It allows subprogram to be separately compiled.Р”В«) Relocatable machine language: It makes the process of code generation easier.Р”В¬) Absolute machine language: It can be placed in a fixed location in memory and can be executed immediately. The target program is the output of the code generator.

The code generation phase needs complete error-free intermediate code as an input requires.

values of names in it can directly manipulated by the machine instructions.

We assume front end produces low-level intermediate representation i.e.

Intermediate representation has the several choices:.

The source program is produced by the front end.

The input to the code generator contains the intermediate representation of the source program and the information of the symbol table.

In the code generation phase, various issues can arises:

Code generation issues in compiler design