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, 69 insertions, 0 deletions

diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index 4615558b912..fffc2dd2b84 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -234,6 +234,14 @@ static Attribute::AttrKind fromRust(LLVMRustAttribute Kind) {
     return Attribute::SanitizeMemTag;
   case ShadowCallStack:
     return Attribute::ShadowCallStack;
+  case AllocSize:
+    return Attribute::AllocSize;
+#if LLVM_VERSION_GE(15, 0)
+  case AllocatedPointer:
+    return Attribute::AllocatedPointer;
+  case AllocAlign:
+    return Attribute::AllocAlign;
+#endif
   }
   report_fatal_error("bad AttributeKind");
 }
@@ -305,6 +313,67 @@ extern "C" LLVMAttributeRef LLVMRustCreateUWTableAttr(LLVMContextRef C, bool Asy
 #endif
 }
 
+extern "C" LLVMAttributeRef LLVMRustCreateAllocSizeAttr(LLVMContextRef C, uint32_t ElementSizeArg) {
+  return wrap(Attribute::getWithAllocSizeArgs(*unwrap(C), ElementSizeArg, None));
+}
+
+#if LLVM_VERSION_GE(15, 0)
+
+// These values **must** match ffi::AllocKindFlags.
+// It _happens_ to match the LLVM values of llvm::AllocFnKind,
+// but that's happenstance and we do explicit conversions before
+// passing them to LLVM.
+enum class LLVMRustAllocKindFlags : uint64_t {
+  Unknown = 0,
+  Alloc = 1,
+  Realloc = 1 << 1,
+  Free = 1 << 2,
+  Uninitialized = 1 << 3,
+  Zeroed = 1 << 4,
+  Aligned = 1 << 5,
+};
+
+static LLVMRustAllocKindFlags operator&(LLVMRustAllocKindFlags A, LLVMRustAllocKindFlags B) {
+  return static_cast<LLVMRustAllocKindFlags>(static_cast<uint64_t>(A) &
+                                      static_cast<uint64_t>(B));
+}
+
+static bool isSet(LLVMRustAllocKindFlags F) { return F != LLVMRustAllocKindFlags::Unknown; }
+
+static llvm::AllocFnKind allocKindFromRust(LLVMRustAllocKindFlags F) {
+  llvm::AllocFnKind AFK = llvm::AllocFnKind::Unknown;
+  if (isSet(F & LLVMRustAllocKindFlags::Alloc)) {
+    AFK |= llvm::AllocFnKind::Alloc;
+  }
+  if (isSet(F & LLVMRustAllocKindFlags::Realloc)) {
+    AFK |= llvm::AllocFnKind::Realloc;
+  }
+  if (isSet(F & LLVMRustAllocKindFlags::Free)) {
+    AFK |= llvm::AllocFnKind::Free;
+  }
+  if (isSet(F & LLVMRustAllocKindFlags::Uninitialized)) {
+    AFK |= llvm::AllocFnKind::Uninitialized;
+  }
+  if (isSet(F & LLVMRustAllocKindFlags::Zeroed)) {
+    AFK |= llvm::AllocFnKind::Zeroed;
+  }
+  if (isSet(F & LLVMRustAllocKindFlags::Aligned)) {
+    AFK |= llvm::AllocFnKind::Aligned;
+  }
+  return AFK;
+}
+#endif
+
+extern "C" LLVMAttributeRef LLVMRustCreateAllocKindAttr(LLVMContextRef C, uint64_t AllocKindArg) {
+#if LLVM_VERSION_GE(15, 0)
+  return wrap(Attribute::get(*unwrap(C), Attribute::AllocKind,
+      static_cast<uint64_t>(allocKindFromRust(static_cast<LLVMRustAllocKindFlags>(AllocKindArg)))));
+#else
+  report_fatal_error(
+      "allockind attributes are new in LLVM 15 and should not be used on older LLVMs");
+#endif
+}
+
 // Enable a fast-math flag
 //
 // https://llvm.org/docs/LangRef.html#fast-math-flags