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notes.md

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Operator Precedence Parsing

  • ParseBinOpRHS(int ExprPrec, std::unique_ptr LHS) will parse the next expression with operator precedence greater than or equal to ExprPrec, given LHS

  • If the precedence of the next token is < required precedence, then the LHS itself is the expression

  • If the precedence of the next token is > required precedence, then process that expression, and then return (op, LHS, processed expr)

  • For accessing ptrs from a vector<unique_ptr>, use for (const auto& x: vec)!

Codegen

  • Value: Anything that can be used as an operand to other values. Instructions, Functions, Constants- are all Values. (I like to think of this as an SSA register)

  • Module contains all information related to an LLVM module- list of global variables, functions, libraries that it depends on, symbol table

  • LLVMContext: An opaque class for isolating different programs being compiled- I could have one program which uses n contexts for compiling n different programs- (a compiler server if you will). The context object can be used to store, get, use llvm constructs related to a particular program.

  • IRBuilder: This provides a uniform API for creating instructions and inserting them into a basic block: either at the end of a BasicBlock, or at a specific iterator location in a block. ref

  • While generating code, you create Calls, Functions, Instructions using the IRBuilder object. But you get Types, Numeric Constants,

  • A Constant inherits Value. To generate a constant numeric value, one creates a constant

  • ArrayRef means "anything that can be accessed using array notation []"

  • Although undocumented, arg_size() returns the number of arguments to function

  • You stupid man- a Function is a Value! So is a CallInst!

  • Apparently, CreateCall cannot fail!- possibly because all it is doing is emitting some code

  • Static class methods can be used without instantiating a class object

  • The innermost error will do LogErrorV- when the error is received from something you call- don't use LogErrorV again.

  • a * a + 2 * a * b + b * b

  • LHS = a, Prec = 0 tokprec = 40, BinOp = *, o

  • The bug was: I was trying to look at precedence of next token before parsing the Primary Expression

  • How the "separate modules for each function" thing works:

The final line above actually creates the IR Function corresponding to the Prototype. This indicates the type, linkage and name to use, as well as which module to insert into. “external linkage” means that the function may be defined outside the current module and/or that it is callable by functions outside the module. The Name passed in is the name the user specified: since “TheModule” is specified, this name is registered in “TheModule”s symbol table.