global is misaligned #4502
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It doesn't crash for me (Win 10 Pro, AMD Ryzen 9 5950X). But the last line does print "random" output every time you run it. etc. |
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I did find a code gen bug by slightly changing the code: package main
import "core:fmt"
import "core:math/rand"
Globals :: struct #align(128) {
padding04: f32,
padding08: f32,
padding12: f32,
padding16: f32,
// padding20: f32,
// padding24: f32,
// padding28: f32,
// padding32: f32,
mat: matrix[4, 4]f32,
}
g := Globals{} // <- struct is misaligned (seems to be stuck on 16 byte alignment)
// compiled with core-avx2
main :: proc() {
g.mat = {
2, -1.0, -1.0, -1.0,
-1.0, 2, -1.0, -1.0,
-1.0, -1.0, 2, -1.0,
-1.0, -1.0, -1.0, 2,
}
mat: matrix[4, 4]f32
for i in 0..<4 {
for j in 0..<4 {
g.mat[i, j] = rand.float32_uniform(1.0, 10.0) // fails to compile
// mat[i, j] = 1 // rand.float32_uniform(1.0, 10.0)
}
}
fmt.println(size_of(matrix[4, 4]f32))
fmt.println(align_of(matrix[4, 4]f32))
fmt.println(size_of(Globals))
fmt.println(align_of(Globals))
struct_memory_as_floats := cast([^]f32)&g
fmt.println("struct address =", rawptr(struct_memory_as_floats))
fmt.println(struct_memory_as_floats[:size_of(Globals) / size_of(f32)])
fmt.println(g.mat * mat) // CRASH: vmovaps ymm, m256 <- not 32 byte aligned
}Which results in: |
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Context
I started using Odin about a year ago, and I love it! I can't stop using it, it's so much better than C/C++. I use it whenever I can.
So far, I haven’t had many issues, but today my luck ran out when I tried to compile my code with AVX instructions. After a bit of debugging, I found that some of my global data was misaligned.
I’ve reduced the code to a small example to reproduce the problem.
Expected Behavior
For the global data to be correctly aligned.
Current Behavior
The global data is misaligned, and the AVX builds are blowing up in my face. :(
Steps to Reproduce
Run the code. add/remove padding to make the struct misaligned.
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