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.

2 files changed, 29 insertions, 0 deletions

diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index f64eb79b0a8..b89408ab75a 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -193,6 +193,9 @@ pub enum AttributeKind {
     SanitizeMemTag = 34,
     NoCfCheck = 35,
     ShadowCallStack = 36,
+    AllocSize = 37,
+    AllocatedPointer = 38,
+    AllocAlign = 39,
 }
 
 /// LLVMIntPredicate
@@ -986,6 +989,22 @@ pub mod debuginfo {
     }
 }
 
+use bitflags::bitflags;
+// These values **must** match with LLVMRustAllocKindFlags
+bitflags! {
+    #[repr(transparent)]
+    #[derive(Default)]
+    pub struct AllocKindFlags : u64 {
+        const Unknown = 0;
+        const Alloc = 1;
+        const Realloc = 1 << 1;
+        const Free = 1 << 2;
+        const Uninitialized = 1 << 3;
+        const Zeroed = 1 << 4;
+        const Aligned = 1 << 5;
+    }
+}
+
 extern "C" {
     pub type ModuleBuffer;
 }
@@ -1193,6 +1212,8 @@ extern "C" {
     pub fn LLVMRustCreateByValAttr<'a>(C: &'a Context, ty: &'a Type) -> &'a Attribute;
     pub fn LLVMRustCreateStructRetAttr<'a>(C: &'a Context, ty: &'a Type) -> &'a Attribute;
     pub fn LLVMRustCreateUWTableAttr(C: &Context, async_: bool) -> &Attribute;
+    pub fn LLVMRustCreateAllocSizeAttr(C: &Context, size_arg: u32) -> &Attribute;
+    pub fn LLVMRustCreateAllocKindAttr(C: &Context, size_arg: u64) -> &Attribute;
 
     // Operations on functions
     pub fn LLVMRustGetOrInsertFunction<'a>(
diff --git a/compiler/rustc_codegen_llvm/src/llvm/mod.rs b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
index 48fbc1de8ee..8e5e1a8b2a3 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
@@ -95,6 +95,14 @@ pub fn CreateUWTableAttr(llcx: &Context, async_: bool) -> &Attribute {
     unsafe { LLVMRustCreateUWTableAttr(llcx, async_) }
 }
 
+pub fn CreateAllocSizeAttr(llcx: &Context, size_arg: u32) -> &Attribute {
+    unsafe { LLVMRustCreateAllocSizeAttr(llcx, size_arg) }
+}
+
+pub fn CreateAllocKindAttr(llcx: &Context, kind_arg: AllocKindFlags) -> &Attribute {
+    unsafe { LLVMRustCreateAllocKindAttr(llcx, kind_arg.bits()) }
+}
+
 #[derive(Copy, Clone)]
 pub enum AttributePlace {
     ReturnValue,