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fix alloca args overwriting eachother

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Brendan Hansknecht 2024-07-20 21:14:31 -07:00
parent a81d4b8b16
commit 703224b275
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1 changed files with 28 additions and 1 deletions
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29
crates/compiler/gen_llvm/src/llvm/build.rs
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@ -3359,27 +3359,54 @@ pub(crate) fn build_exp_stmt<'a, 'ctx>(
let current_block = builder.get_insert_block().unwrap();
let mut to_resolve = bumpalo::vec![in env.arena];
for (joinpoint_arg, argument) in joinpoint_args.iter().zip(arguments.iter()) {
let (value, layout) = scope.load_symbol_and_layout(argument);
match joinpoint_arg {
crate::llvm::scope::JoinPointArg::Alloca(alloca) => {
let (size, alignment) = layout_interner.stack_size_and_alignment(layout);
// I would like to just do a direct memcpy here, but it is not valid.
// Imagine the case where I just swap two referenced args.
// (a, b) -> jump (b, a)
// This would generate `a` overwriting `b` then `b` overwriting `a`.
// That would lead to both values being `b`
// Instead we copy to a tmp alloca here.
// After we have all tmp allocas, we copy those to the final output.
let basic_type = basic_type_from_layout(
env,
layout_interner,
layout_interner.get_repr(layout),
);
let tmp = create_entry_block_alloca(env, basic_type, "tmp_output_for_jmp");
builder
.build_memcpy(
*alloca,
tmp,
alignment,
value.into_pointer_value(),
alignment,
env.ptr_int().const_int(size as _, false),
)
.unwrap();
to_resolve.push((alloca, tmp, alignment, size));
}
crate::llvm::scope::JoinPointArg::Phi(phi) => {
phi.add_incoming(&[(&value, current_block)]);
}
}
}
for (alloca, tmp, alignment, size) in to_resolve {
builder
.build_memcpy(
*alloca,
alignment,
tmp,
alignment,
env.ptr_int().const_int(size as _, false),
)
.unwrap();
}
builder.new_build_unconditional_branch(*cont_block);