add C example, handwritten example, and generic tester #5
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| i64 reverse_bytes(i64 a){ | ||
| i64 b = 0; | ||
| b += (a & 0xff00000000000000)>>56; |
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Replace += with |= and magic happens: https://godbolt.org/z/GYL1L0
Unfortunately, wasm does not have bswap support.
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Cool!
But Wasm has no bswap opcode. I would have to look at the output wasm, but don't think there is a difference since addition + and or | both use the ALU in one cycle.
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| // call function based on selector value | ||
| switch (*selector) { | ||
| case 0x1a029399: |
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I'm curious, why are the selector values here different from those in the example pseudo-code for this repository?
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I think that you are referring to the wrc20 spec https://gist.github.com/axic/16158c5c88fbc7b1d09dfa8c658bc363 where the selector has value 0x9993021a. The selector here is reversed because callDataCopy() puts the call data into wasm memory, and Wasm reverses the bytes when it loads/stores memory to the stack. I could have also done reverse_bytes() on selector and used the same selector byte-ordering as the wrc20 spec.
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Please do not merge yet. I am not sure that people want source code in this repo. It may be better to just have a spec, a tester, and links to implementations. Any thoughts? In this PR, wrc20.c, the tester, and the handwritten examples now live in the C_ewasm_contracts repo. So I think that this PR should be closed, and another one opened with just the tester. |
| .PHONY: all | ||
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| #LLVM_BUILD_DIR=/path/to/llvm-build | ||
| LLVM_BUILD_DIR=/home/user/repos/benchmarking/wasmception/build/llvm |
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I believe the upstream LLVM has wasm target enabled by default. How do you want to handle the LLVM installation?
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This PR is old and outdated. I don't want this repo to include the wrc20.c code anymore. I think that this PR should be closed, but am waiting for feedback before I close.
This is a great question which I need advice for in the current wrc20.c repo https://github.com/poemm/C_ewasm_contracts . It is good that newer version of ubuntu have LLVM 8+ by default. But getting LLVM 8+ may be a challenge for some users. The linked repo gives instructions in the README and compilation commands in the Makefile, but, in my experience, I have had to restart the compilation several times before it finished. Maybe this conversation should be moved to that repo, but I am happy to continue here.
Ideally we can ditch These are much more concise and human-readable than state tests. Current limitations of Truffle revolve around Here's what I've done so far to the C contract to reflect the issues I just mentioned: https://github.com/ewasm/wrc20-examples/pull/8/files#diff-cce65dd672810c34ebe43a8482583861 |
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