| Commit message (Collapse) | Author | Age | Files | Lines |
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New convention: compare 'with' for asymmetric comparisons (greater or lesser
than), and compare 'and' for symmetric comparisons. Worth making this distinction
even though the opcodes are identical; when we compare 'with', the order
of operands is significant.
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Considering how much trouble a merge phase would be (commit 4978), it seems
simpler to just add the extra syntax for controlling the entry point of
the generated ELF binary.
But I wouldn't have noticed this if I hadn't taken the time to write out
the commit messages of 4976 and 4978.
Even if we happened to already have linked list primitives built, this
may still be a good idea considering that I'm saving quite a lot of code
in duplicated entrypoints.
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We only can't use rm32=5 when mod=0. Totally fine when it's mod=1.
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Some automated commenting cleanup. Still needs more careful manual scanning.
sed -i 's/^# 1-3/# . 1-3/' *.subx */*.subx
sed -i 's/^# op/# . op/' *.subx */*.subx
sed -i 's/# vim/# . . vim/' *.subx */*.subx
sed -i 's/^ # push args/ # . . push args/' *.subx */*.subx
sed -i 's/^ # discard args/ # . . discard args/' *.subx */*.subx
sed -i 's/^ # call/ # . . call/' *.subx */*.subx
sed -i 's/^ # prolog/ # . prolog/' *.subx */*.subx
sed -i 's/^ # epilog/ # . epilog/' *.subx */*.subx
sed -i 's/^ # save registers/ # . save registers/' *.subx */*.subx
sed -i 's/^ # restore registers/ # . restore registers/' *.subx */*.subx
sed -i 's/ operand / register /' *.subx */*.subx
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Reindent all SubX code to make some room for the new comment style.
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Standardize on hyphens in all names.
And we'll use colons for namespacing labels in functions.
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Start requiring a '-o' flag to designate the output binary when translating.
Things currently get funky if you pass in multiple inputs, but that's ok.
This is the first step to supporting multiple input files for a single
output binary.
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More calling convention tweaks.
Use EBP to get consistently at parameters and locals.
Always put the first function argument closest to EBP.
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One of the more painful things I had to debug with machine code. Tricks
I used can be seen in ex10.subx:
- printing argv[1] in various places
- printing a single 'X' in various places to count how many times we get
to different instructions
- exiting with the current value of EAX in various places
I repeatedly went down the wrong trail in several ways:
- forgetting that the problem lay in native runs, and accidentally switching
to subx runs during debugging.
- forgetting to pass commandline args, because ex10 doesn't check its argv
- writing the wrong comment for an instruction, and then miscalculating
the set of registers that need to be saved.
- forgetting that syscalls clobber EAX.
Debugging native runs is hard, because you have to write non-trivial code
to instrument the binary, and instrumentation can itself be buggy.
When we finally tracked it down, I recognized the problem immediately.
I'd meant to confirm the behavior of opcode 8a against bare metal, and
then forgot.
In any case, opcode 8a was inconsistent with 88. Sloppy.
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Even more cuddling. We want to keep lines short where the opcode and operands
are self-explanatory.
If there are any implicit registers, etc., we'll continue to do the table
layout.
The first two columns look messy now; let's see how this goes.
Maybe I'll give up on the tabular layout altogether, just string args with
a single space.
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New example program: ascii null-terminated string comparison
I'd hoped this would be a stepping stone to supporting general ascii comparison,
but we're planning to use size-prefixed rather than null-terminated arrays
everywhere. The only exception is commandline arguments, which will remain
null-terminated to interoperate with Linux.
So I'm going to need separate functions for "compare with argv" and for
general string comparison.
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