Welcome to Chapter 5 of the “ Implementing a language with LLVM” tutorial. . To visualize the control flow graph, you can use a nifty feature of the LLVM ‘opt’. adding optimizer support to your language, and adding JIT compiler support. Once we have a parser, we’ll define and build an Abstract Syntax Tree (AST).
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7. Kaleidoscope: Extending the Language: Mutable Variables — LLVM 8 documentation
For a better example, the parenthesis operator is defined like this:. This wraps up the third chapter of the Kaleidoscope tutorial. Each token returned by our lexer will be one of the token variant values.
Create TheContext”ifcont” ; Builder. CreateFAdd LR”addtmp” ; case ‘-‘: While we could do it this way, the most important kaleidocsope of parentheses are to guide the parser and provide grouping.
CreateLoad KaaleidoscopeName. Now that we have all of our simple expression-parsing logic in place, we can define a helper function to wrap it together into one entry point. Start return nullptr ; if CurTok! Kaleidoscope does this with a pattern match and a helper function. To build this example, use:.
This function does a variety of consistency checks on the generated code, to determine if our compiler is doing everything right. A more interesting example is included in Chapter 6 where we write a little Kaleidoscope application that displays a Mandelbrot Set at various levels of magnification.
This is all pretty straight-forward code for processing input. VarName VarNameStart std:: At this point, we know that the binary operator to the RHS of our primary has higher precedence than the binop we are currently parsing.
Now the code starts to get more interesting. Right now we only create the AST, so there are no useful accessor methods on them. First, we define the possibilities: Become a Redditor and subscribe to one of thousands of communities. Because calling codegen recursively could arbitrarily change the notion of the current block, we are required to get an up-to-date value for code that will set up kaleicoscope Phi node.
Well, that was easy: One thing that is nice about our AST is that it captures the language features without talking about the syntax of the language.
If not, it sets the step value to null in the AST node:. In practice, we recommend always using IRBuilder when generating code like this.
First, we define the possibilities:. V return nullptr; if CurTok!
First we add new enum values for the relevant tokens: Now we can produce simple output to the console by using things like: The gettok function is called to return the next token from standard input. Now that we have the relevant tokens coming from the lexer and we have the AST node to build, our parsing logic is relatively straightforward. All of these changes are isolated in the Kaleidoscope code generator. If the current token is an identifier, kaleidozcope IdentifierStr global variable holds kaeidoscope name of the identifier.
The GetTokPrecedence function returns the precedence for the current token, or -1 if the token is not a binary operator.
The first line gets the current Function object that is being built. With this, we have the complete lexer for the basic Kaleidoscope language the full code listing for the Lexer is available in the next chapter of the tutorial.
In the case above, the whole loop body is one block, but remember that the body code itself could consist of multiple blocks e. Now that the body is emitted, we compute the next value of the iteration variable by adding the step value, or 1. This uses look-ahead to determine which sort of expression is being inspected, and then parses it with a function call. This will let us cover a fairly broad range of language design and LLVM-specific usage issues, showing and explaining the code for it all along the way, without overwhelming you with tons of details up front.
The NamedValues map keeps track of which values are defined in the current scope and what their LLVM representation is. Using this technique is:. This means, there is no difference between JIT compiled code and native machine code that is statically linked into your application.