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WebAssebly misaligned load test
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| clang -cc1 -emit-llvm-bc -triple=wasm32-unknown-unknown-wasm -std=c11 test.c | |
| llc -filetype=obj test.bc -o test.o | |
| wasm-ld --no-entry test.o -o test.wasm --export=aligned --export=misaligned --import-memory | |
| wasm2wat test.wasm |
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| const char a[] = {1,2,3,4,5,6,7,8}; | |
| int aligned(int i) | |
| { | |
| const int start = i % 3; | |
| int value = ((int)a[start] << 0) + ((int)a[start + 1] << 8) + ((int)a[start + 2] << 16) + ((int)a[start + 3] << 24); | |
| return i * value; | |
| } | |
| int misaligned(int i) | |
| { | |
| return i * (*(int*)(a + (i%3))); | |
| } |
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| <!doctype html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>WASM aligned read test</title> | |
| </head> | |
| <body> | |
| <script> | |
| async function main() { | |
| const resp = await fetch('test.wasm'); | |
| const wasm = await resp.arrayBuffer(); | |
| const memory = new WebAssembly.Memory({initial:10, maximum:100}); | |
| const module = await WebAssembly.instantiate(wasm, { env: { memory } }); | |
| const iterations = 100000000; | |
| let start = new Date(); | |
| for (let i = 0; i < iterations; ++i) { | |
| module.instance.exports.aligned(i); | |
| } | |
| console.log('aligned'); | |
| console.log(new Date() - start); | |
| start = new Date(); | |
| for (let i = 0; i < iterations; ++i) { | |
| module.instance.exports.misaligned(i); | |
| } | |
| console.log('misaligned'); | |
| console.log(new Date() - start); | |
| }; | |
| main(); | |
| </script> | |
| </body> | |
| </html> |
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