add a higher-level IL to use as a target for source2il
#21
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`spec` is updated too.
It covers everything relevant to the lowering pass (unless I missed something). The output uses a shorter formatting that doesn't match what `pretty` produces -- a separate change for supporting S-expr normalization in the tester will be necessary.
It's fully functional (according to the test suite), though not very optimized, both in terms of output it produces and how it does so.
It's a run-of-the-mill test runner. Given the repetition, common parts of the test runners should move into a separate module at one point.
The necessary runner support for disabling execution is still missing, and the test would only result in an infinite loop.
The result stays the same, but how one gets there changes. There are no "implicit parameter", only "implicit arguments". Attaching the implicitness to the callee (i.e., target block) rather than the caller (i.e., block exit) precludes some future optimizations, such as merging basic blocks, in addition to just being wrong conceptually.
Only loops are iterated twice now, greatly reducing the time the pass takes when there are no loops. Further optimizations are possible, such as not following the back edge when there are no changes, but are not implemented yet. The documentation is also improved a bit.
A single-block `Loop` resulted in the forward propagation pass getting stuck.
The test runner now supports the `--compileOnly` argument, which disables validation and execution of the produced VM bytecode.
It didn't reflect reality.
This fixes the test failures.
Pinned locals are now only passed through to blocks/continuations that perform an indirect memory access.
Procedure parameters must unconditionally be registered with the first basic block.
Some of the pinned local tests trigger an illegal access error at run- time, which is fine.
The new name more accurately describes which locals the set contains.
Some `.expected` files were not marked as storing S-expressions.
| (Continuation (Params) (Locals) | ||
| (Continue 1 (List))) | ||
| (Continuation (Params) (Locals) | ||
| (Drop (IntVal 100)) |
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Sorry for what is undoubtedly a silly question, but I checked out what opcDrop does and I can't figure out why we want a <value> operand for the op code, it seems unused. Is the idea that in the future it'll be possible to specify the number of items, or the address (?), we want to drop?
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opcDrop pops and discard the last operand from the operand stack, it's purpose is to remove operand from the stack without having to assign them to a dummy local. The Drop operation has the same role as discard, that is, it evaluates the operand but discards the result.
(Drop (IntVal 100)) just means "discard the integer value 100". I've used it as form of "marker", since it's a simple, short, and side-effect-free statement. The idea is to us them to make sure that statements are placed correctly in the continuations after splitting up the statement list(s).
Co-authored-by: Saem Ghani <[email protected]>
Summary
Add the
L10intermediate language, which is the first IL notstructured around basic blocks (i.e., continuations). The
pass10pass lowers it into the
L4language.Details
Motivation
Directly translating the source language into a language with explicit
basic blocks is hard.
L10is intended to bridge the gap between thesource language and
L4.Language
The name
L10is chosen so that there's still space for more ILs. Itdoes away with the basic-block centered structure, instead providing
higher- level control-flow constructs such as
if,case, andloop.A
try/exceptlike facility is currently missing, meaning thatexception handling (where
Raiseis used) cannot be expressed.Some way to delimit lifetimes of locals is also missing. Locals are
currently treated as being alive for the whole duration, which can lead
to locals that have their address taken being kept alive longer than
necessary.
Apart from the new control-flow constructs,
L10stays close toL4,so that the lowering can focus on the splitting the procedure into
basic blocks.
To-Do
t01_looptest workNotes For Reviewers
try/exceptlike facility can be added later on with ease