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| author | Kaz Kylheku <kaz@kylheku.com> | 2021-09-29 22:46:01 -0700 |
|---|---|---|
| committer | Kaz Kylheku <kaz@kylheku.com> | 2021-09-29 22:46:01 -0700 |
| commit | 68f856fc1fe2f662e3771bec32fb447304c56818 (patch) | |
| tree | 010d45e223c62a54568f01392da7ef7042d7d7c8 /stdlib | |
| parent | b9398943c06b8d0503f71eda56c59dcd36e826e2 (diff) | |
| download | txr-68f856fc1fe2f662e3771bec32fb447304c56818.tar.gz txr-68f856fc1fe2f662e3771bec32fb447304c56818.tar.bz2 txr-68f856fc1fe2f662e3771bec32fb447304c56818.zip | |
compiler: remove impossible cases in jump threading.
* stdlib/optimize.tl (basic-blocks thread-jumps-block): There
can't be any instructions in a basic block after an if or ifq,
so in these cases, jrest is always nil. Let's ignore that nil
efficiently with @nil, and get rid of the cut-block branches
of the code. There is a similar case in peephole-block, but
the target of the jump is an (end ...) which doesn't
necessarily end a basic block. I temporarily put in an (assert
(null jrest)), and, surprisingly, it never went off during a
rebuild of the library or running of the test case. Still,
only a jend ends a basic block; it would not be correct to
simplify it like these two cases in thread-jumps-block.
Diffstat (limited to 'stdlib')
| -rw-r--r-- | stdlib/optimize.tl | 12 |
1 files changed, 4 insertions, 8 deletions
diff --git a/stdlib/optimize.tl b/stdlib/optimize.tl index db069efa..5f81bc10 100644 --- a/stdlib/optimize.tl +++ b/stdlib/optimize.tl @@ -309,10 +309,8 @@ (jmp @(and @jjlabel @(not @jlabel))) . @nil) ^(if ,reg ,jjlabel)) ((@jlabel - (ifq @reg (t 0) @jjlabel) . @jrest) - (let ((xbl (if jrest - bb.(cut-block [bb.hash jlabel] jrest jinsns) - bb.(next-block [bb.hash jlabel])))) + (ifq @reg (t 0) @jjlabel) . @nil) + (let ((xbl bb.(next-block [bb.hash jlabel]))) (if xbl ^(if ,reg ,xbl.label) insn))) @@ -326,10 +324,8 @@ ^(ifq ,reg ,creg ,jjlabel)) ((@(require @jlabel (equal creg '(t 0))) (if @reg - @(and @jjlabel @(not @jlabel))) . @jrest) - (let ((xbl (if jrest - bb.(cut-block [bb.hash jlabel] jrest jinsns) - bb.(next-block [bb.hash jlabel])))) + @(and @jjlabel @(not @jlabel))) . @nil) + (let ((xbl bb.(next-block [bb.hash jlabel]))) (if xbl ^(ifq ,reg ,creg ,xbl.label) insn))) |