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stop zeroing out alloca's

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Folkert 2022-03-26 18:51:54 +01:00
parent 75ab8afc2b
commit 79dfd23513
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1 changed files with 1 additions and 22 deletions
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23
compiler/gen_llvm/src/llvm/build.rs
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@ -1458,29 +1458,8 @@ pub fn entry_block_alloca_zerofill<'a, 'ctx, 'env>(
.unwrap()
.get_parent()
.unwrap();
let result_alloca = create_entry_block_alloca(env, parent, basic_type, name);
// Initialize all memory of the alloca. This _should_ not be required, but currently
// LLVM can access uninitialized memory after applying some optimizations. Hopefully
// we can in the future adjust code gen so this is no longer an issue.
//
// An example is
//
// main : Task.Task {} []
// main =
// when List.len [ Ok "foo", Err 42, Ok "spam" ] is
// n -> Task.putLine (Str.fromInt n)
//
// Here the decrement function of result must first check it's an Ok tag,
// then defers to string decrement, which must check is the string is small or large
//
// After inlining, those checks are combined. That means that even if the tag is Err,
// a check is done on the "string" to see if it is big or small, which will touch the
// uninitialized memory.
let all_zeros = basic_type.const_zero();
env.builder.build_store(result_alloca, all_zeros);
result_alloca
create_entry_block_alloca(env, parent, basic_type, name)
}
fn build_tag_field_value<'a, 'ctx, 'env>(