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Diffstat (limited to 'chapter18')
| -rw-r--r-- | chapter18/README.md | 41 |
1 files changed, 23 insertions, 18 deletions
diff --git a/chapter18/README.md b/chapter18/README.md index 42f76227..5691059f 100644 --- a/chapter18/README.md +++ b/chapter18/README.md @@ -1,7 +1,11 @@ # Chapter 18: Functions +[Previous: Chapter 17](../chapter17/README.md) | +[Next: Chapter 19](../chapter19/README.md) + # Table of Contents + 1. [FunctionTypes](#function-and-rpc-types) 2. [Return Program Counters](#return-program-counters) 3. [Functions](#functions) @@ -24,7 +28,7 @@ Highlights of the changes: - The top-level is now a call to function `main`, and this changed most tests. - A top-level compile driver, which enforces optimization steps. - A local scheduler. -- A new evaluator which relies on at code motion, both global and local. +- A new evaluator which relies on code motion, both global and local. - A graphic animated viewer for peepholes. Functions are *not* closures in this chapter; that brings about far more @@ -43,7 +47,7 @@ constant. This generally includes e.g. recursive function pointers. A leading `{` character denotes the start of a function or function type, then a list of argument types, and an arrow `->` and the return type. -Functions variables are normal variables and assigned the same way: +Function variables are normal variables and assigned the same way: `functiontype fcn = function-typed-expr;` @@ -84,7 +88,7 @@ scope, so for now these are only used in the evaluator. ## Functions -Functions themselves using the same syntax with as function types, but filled in: +Functions themselves use the same syntax as function types, but filled in: ``` { flt x, flt y -> // Signature @@ -102,13 +106,13 @@ Used in a declaration statement: With `var`: ``` -var dist = { flt x, flt y -> sqrt(x*x*,y*y); } +var dist = { flt x, flt y -> sqrt(x*x+y*y); } ``` Functions are called in the usual way: `dist( 1.2, 2.3 ) // yields 2.59422435` -Functions can have zero arguments, in which case the `->` argument seperator is +Functions can have zero arguments, in which case the `->` argument separator is optional. This allows any section of code to be "thunked" by wrapping it in `{}`. @@ -121,7 +125,7 @@ Called: Functions are always anonymous. When finally assigned to a variable, they will pick up the variable name for debugging and display purposes, but this has no -semantics meaning. Here is a function variable referring to more than one +semantic meaning. Here is a function variable referring to more than one anonymous function; the resulting function either doubles or squares: `val fcn = arg ? { int x -> x+x; } : { int x -> x*x; };` @@ -130,9 +134,9 @@ anonymous function; the resulting function either doubles or squares: Functions can be recursive: ``` -val fact = { int n -> - n <=1 ? n : n*fact(n-1); -}; +val fact = { int n -> + n <=1 ? n : n*fact(n-1); +}; return fact(4); // Returns 4! or 24 ``` @@ -179,7 +183,7 @@ After a `Call` is a `CallEndNode`, internally abbreviated as `cend`. The `CallEnd` will take the `Call` as an input, and also every *linked* function: functions the call-site *knows* it will call. This will be expanded later to be a conservative approximation to the *Call Graph*, with each `CallEnd` -*linked* to ever function it *may* call; if a function is not linked it can not +*linked* to every function it *may* call; if a function is not linked it can not be called from here. This requires a global analysis (fast, cheap, incremental, and global), not in this chapter. So for the moment we only link exact constant functions. @@ -204,8 +208,8 @@ programs. The phases (for now) are: reports on failed null checks. - *Schedule* - Global Code Motion scheduler. After this phase, all nodes belong in some basic block, with the normal suspect CFGNodes being basic blocks. -- *LocalSched* - a local scheduler. Its completely naive, except it enforces - some required rules: Phis appear at block heads, branchs at block exits. +- *LocalSched* - a local scheduler. It's completely naive, except it enforces + some required rules: Phis appear at block heads, branches at block exits. There's room in the algorithm for a much more sophisticated list scheduler. The `Eval2` evaluator requires this information. - *RegAlloc* - Not implemented (yet). @@ -214,7 +218,7 @@ Several globals moved from the Parser to CodeGen, and probably several others ought to move here. There is a very nice `toString()` here; hovering over the `code` variable in -the debug winow will pretty-print the IR "as if" globally scheduled, and the +the debug window will pretty-print the IR "as if" globally scheduled, and the code becomes very readable. @@ -229,12 +233,13 @@ recursive calls). ## Graph Visualizer -Run as `make view`, type your program in the text box, click -outside the box and then use the arrow keys to view IR generator both forwards -and backwards. +Run `make view`, type your program in the text box, and click **Compile** +(or press **Ctrl+Enter**). Use the Left/Right arrow keys to step through graph +construction and optimization. See the [shared viewer guide](../graph/README.md). -Nodes are color coded according to type, same as the lattice diagrams. Nodes -are shaped according to node function as well. At the bottom are `ScopeNode`s, +Nodes use colors and shapes for their graph roles: control, data, memory, Phis, +and scopes. This palette is distinct from the type-lattice diagrams. The viewer +also displays `ScopeNode`s, which only exist for the Parser but are actual Nodes and have `use->def` edges into the IR. |