codegen: use new {re,de,}allocator annotations in llvm

This obviates the patch that teaches LLVM internals about
_rust_{re,de}alloc functions by putting annotations directly in the IR
for the optimizer.

The sole test change is required to anchor FileCheck to the body of the
`box_uninitialized` method, so it doesn't see the `allocalign` on
`__rust_alloc` and get mad about the string `alloca` showing up. Since I
was there anyway, I added some checks on the attributes to prove the
right attributes got set.

While we're here, we also emit allocator attributes on
__rust_alloc_zeroed. This should allow LLVM to perform more
optimizations for zeroed blocks, and probably fixes #90032. [This
comment](https://github.com/rust-lang/rust/issues/24194#issuecomment-308791157)
mentions "weird UB-like behaviour with bitvec iterators in
rustc_data_structures" so we may need to back this change out if things
go wrong.

The new test cases require LLVM 15, so we copy them into LLVM
14-supporting versions, which we can delete when we drop LLVM 14.

1 files changed, 3 insertions, 0 deletions

diff --git a/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h b/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h
index bca5425e728..93f302b44e8 100644
--- a/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h
+++ b/compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h
@@ -86,6 +86,9 @@ enum LLVMRustAttribute {
   SanitizeMemTag = 34,
   NoCfCheck = 35,
   ShadowCallStack = 36,
+  AllocSize = 37,
+  AllocatedPointer = 38,
+  AllocAlign = 39,
 };
 
 typedef struct OpaqueRustString *RustStringRef;