two pass encoding and resizing references #22

omicron · 2025-04-24T13:04:24Z

omicron commented

2025-04-24 13:04:24 +00:00

Implements a two pass encoding

First pass:

Run through the AST and collect information:
- Set register values
- Parse/set number values
- Mark all instructions that use label references
Encode all instructions that don't use label references
Update addresses of all labels and instructions. Use an estimated
instruction size for those instructions that use label references.

Second pass:

Run through the AST for all instructions that use label references and
collect size information using the estimated addresses from pass 1
Encode label references with the estimated addresses, this fixes their
size.
Update all addresses

Iteration: Repeat the second pass until addresses converge

This fixes #14

Implements a two pass encoding First pass: - Run through the AST and collect information: - Set register values - Parse/set number values - Mark all instructions that use label references - Encode all instructions that don't use label references - Update addresses of all labels and instructions. Use an estimated instruction size for those instructions that use label references. Second pass: - Run through the AST for all instructions that use label references and collect size information using the estimated addresses from pass 1 - Encode label references with the estimated addresses, this fixes their size. - Update all addresses Iteration: Repeat the second pass until addresses converge This fixes #14

omicron added 6 commits 2025-04-24 13:04:24 +00:00

Fix parse_memory_expression to use parse_label_reference

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530e3fb423

Symbol table now keeps track of label statements 9c6b69e187

Before it kept track of a more specific node that referenced the symbol
in some way. Now it will only keep track of the actual label defining
statements. This is done to facilitate encoding. The encoder can now go
from a symbol name to the statement that defines the symbol.

Restructure the encoder to deal with this and pass the correct statement
to the symbol update function.

Update symbols tests for new API 0acc3f27f3

Add more values to the ast to facilitate encoding 5272fdb227

- Add a instruction value that contains the encoding, the address and a
  flag to indicate if this instruction contains label references
- Add label value that contains an address
- Add reference value that contains offset, an absolute address and an
  operand size
- define types for all value options in the union
- define accessor functions for all the values in the union

Implement two pass encoding c848995ad6

First pass:
 - collect information for numbers, registers and which instructions
   contain label references
 - encode all instructions that don't contain label references
 - Set (temporary) addresses for each instruction

Second pass:
 - Collect information about label references (address, offset, size)
 - encode all instructions that contain label references
 - Update (if necessary) addresses for each instruction

 The second pass is iterated 10 times or until no instructions change
 size, whichever comes first.

Implement one immediate label reference operand

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Details

7cefc3564d

Also adds opcode data for jmp and call

omicron merged commit 7cefc3564d into main

2025-04-24 13:05:47 +00:00

omicron deleted branch encoding_start

2025-04-24 13:05:47 +00:00

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Reference: omicron/oas#22