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Diffstat (limited to 'chapter18/README.md')
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diff --git a/chapter18/README.md b/chapter18/README.md index 9b13e277..578ed7d4 100644 --- a/chapter18/README.md +++ b/chapter18/README.md @@ -81,8 +81,7 @@ es[1] = 9; return find(es,9); // 1 ``` -All reachable results of one function must have a common type. This is checked -after optimization, so an unreachable return does not cause a type error. +Return types are generally inferred, so all returns must have a common type. There is no `void` type although a function can return `null` with no syntax, and callers can ignore a result by using the call as a statement. @@ -161,10 +160,10 @@ body contains branches, loops, and several return statements. ### Calls and return points [CallNode](src/main/java/com/seaofnodes/simple/node/CallNode.java) takes inputs -`{control, memory, arguments..., function pointer}`. The final input determines -the target; it can be a constant function or the result of a function-valued -expression. Argument expressions are evaluated before the Call takes its -control and memory inputs. +`{control, memory, arguments..., function pointer}`. The final input +determines the target; it can be a constant function or the result of a +function-valued expression. Argument expressions are evaluated in order before the Call +takes its control and memory inputs. Each Call has a [CallEndNode](src/main/java/com/seaofnodes/simple/node/CallEndNode.java), the point where its caller continues. CallEnd takes the Call and the Returns @@ -323,8 +322,9 @@ compilation process and its function lookup table. It enforces the phase order: | Phase | Purpose | |---|---| | Parse | Build the functions and calls directly in the IR. | -| Opto | Iterate peepholes, including call linking and trivial inlining. | +| Iter | Iterate peepholes, including call linking and trivial inlining. | | TypeCheck | Check the surviving graph after types and dead control have settled. | +| LoopTree | Discover loop nesting and connect nonreturning loops with synthetic exits. | | Schedule | Use global code motion to place operations in basic blocks. | | LocalSched | Order operations within each block for execution. | @@ -332,9 +332,25 @@ For example: ```java CodeGen code = new CodeGen("val sq = { int x -> x*x; }; return sq(arg);"); -code.parse().opto().typeCheck().GCM().localSched(); +code.driver(CodeGen.Phase.TypeCheck); ``` +With six stages, writing the whole call chain at every use obscures what the +caller needs. `driver(target)` runs the missing phases in order and stops at +the requested stage. A later call resumes from there; asking for an already +completed stage does not rerun it: + +```java +code.driver(CodeGen.Phase.LoopTree); // Ready to inspect loops. +code.driver(CodeGen.Phase.LocalSched); // Finish scheduling. +``` + +Short tests can still say `code.parse().iter()` to show exactly what they test. +`Iter` is the worklist solve introduced in Chapter 9; an optimistic `Opto` +phase arrives with SCCP in Chapter 24. Phase entry points check ordering and +report their completion to the graph viewer. Loop-tree construction is now +an explicit entry point instead of work hidden inside GCM. + Global code motion extends the work of [Chapter 13](../chapter13/README.md) to multiple functions. It keeps their bodies separate, gives shared constant expressions a local copy in each function that uses them, and respects memory |