Improve handling of lifetime intrinsics once more #27999
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The issues that the comments referred to were fixed before the PR even landed but we never got around to remove the hack of skipping the lifetime start.
Combining them seemed like a good idea at the time, but turns out that handling lifetimes separately makes it somewhat easier to handle cases where we don't want the intrinsics, and let's you see more easily where the start/end pairs are.
… items Function arguments are live for the whole function scope, so adding lifetime intrinsics around them adds no value. The same is true for drop hint allocas and everything else that goes directly through lvalue_scratch_datum. So the easiest fix is to emit lifetime intrinsics only for lvalue datums that are created in to_lvalue_datum_in_scope(). The reduces peak memory usage and LLVM times by about 1-4%, depending on the crate.
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@bors r+ |
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The major change here is in the tiny commit at the end and makes it so that we no longer emit lifetime intrinsics for allocas for function arguments. They are live for the whole function anyway, so the intrinsics add no value. This makes the resulting IR more clear, and reduces the peak memory usage and LLVM times by about 1-4%, depending on the crate. The remaining changes are just preparatory cleanups and fixes for missing lifetime intrinsics.
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The major change here is in the tiny commit at the end and makes it so that we no longer emit lifetime intrinsics for allocas for function arguments. They are live for the whole function anyway, so the intrinsics add no value. This makes the resulting IR more clear, and reduces the peak memory usage and LLVM times by about 1-4%, depending on the crate.
The remaining changes are just preparatory cleanups and fixes for missing lifetime intrinsics.