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Add dead code elimination and folding of constant conditionals

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This commit is contained in:
John Lorentzson 2025-07-31 13:08:11 +02:00
parent 15898ab691
commit f3cbadfa54
2 changed files with 32 additions and 2 deletions
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6
user-side-compiler/interface.lisp
View file

@ -66,8 +66,12 @@
(do-iblocks (ib start-iblock) (do-iblocks (ib start-iblock)
(optim-reorder-arguments ib) (optim-reorder-arguments ib)
(optim-trivial-constant-folding ib) (optim-trivial-constant-folding ib)
(optim-constant-conditional ib)
(optim-call-duplicate-args ib) (optim-call-duplicate-args ib)
(optim-remove-unused ib))) (optim-remove-unused-instructions ib))
(optim-dead-code-elimination start-iblock)
(do-iblocks (ib start-iblock)
(optim-remove-unused-instructions ib)))
(defun ci-allocation-info (allocs) (defun ci-allocation-info (allocs)
(format *debug-io* "Values: ~D~%" (length allocs)) (format *debug-io* "Values: ~D~%" (length allocs))

28
user-side-compiler/middle/optimizations.lisp
View file

@ -58,6 +58,22 @@
inst) inst)
(delete-instruction inst))))))) (delete-instruction inst)))))))
(defun optim-constant-conditional (iblock)
(do-instructions (inst iblock)
(when (and (typep inst 'ir-if) (ir-constant-p (input inst)))
(let ((then-block (first (destinations inst)))
(else-block (second (destinations inst)))
(falsep (zerop (ir-constant-value (input inst)))))
(replace-terminator
inst
(make-instance 'ir-jump :destinations (list (if falsep
else-block
then-block))
:source (source inst)))
(dolist (input (inputs inst))
(when (typep input 'ir-data)
(remove-user input inst)))))))
(defun optim-commutative-constant-folding (iblock) (defun optim-commutative-constant-folding (iblock)
"Attempts to replace operations with compile-time computed constants." "Attempts to replace operations with compile-time computed constants."
(do-instructions (inst iblock) (do-instructions (inst iblock)
@ -161,7 +177,7 @@ that uses them to assist in generating more direct 6502 code."
before being cut off. This ensures that it can't get stuck forever, even before being cut off. This ensures that it can't get stuck forever, even
though I'm pretty sure it can't anyway.") though I'm pretty sure it can't anyway.")
(defun optim-remove-unused (iblock) (defun optim-remove-unused-instructions (iblock)
(let ((to-delete '())) (let ((to-delete '()))
(loop :repeat +optim-remove-unused-max-passes+ ; this many times or fewer (loop :repeat +optim-remove-unused-max-passes+ ; this many times or fewer
:do (setf to-delete '()) :do (setf to-delete '())
@ -174,6 +190,16 @@ though I'm pretty sure it can't anyway.")
(mapc 'delete-instruction to-delete) (mapc 'delete-instruction to-delete)
:until (null to-delete)))) :until (null to-delete))))
(defun optim-dead-code-elimination (start-iblock)
(let ((reachable (list start-iblock)))
(do-iblocks (iblock start-iblock)
(dolist (dest (destinations (end iblock)))
(push dest reachable)))
(do-iblocks (iblock start-iblock)
(unless (member iblock reachable)
(setf (next (prev iblock))
(next iblock))))))
(defun optim-call-duplicate-args (iblock) (defun optim-call-duplicate-args (iblock)
"Attempts to deduplicate call arguments." "Attempts to deduplicate call arguments."
(let ((calls '())) (let ((calls '()))