Rollup merge of #137549 - oli-obk:llvm-ffi, r=davidtwco

Clean up various LLVM FFI things in codegen_llvm

cc ```@ZuseZ4``` I touched some autodiff parts

The major change of this PR is [bfd88ce](https://github.com/rust-lang/rust/pull/137549/commits/bfd88cead0dd79717f123ad7e9a26ecad88653cb) which makes `CodegenCx` generic just like `GenericBuilder`

The other commits mostly took advantage of the new feature of making extern functions safe, but also just used some wrappers that were already there and shrunk unsafe blocks.

best reviewed commit-by-commit

2 files changed, 18 insertions, 7 deletions

diff --git a/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
index 25ca3498803..f6b23862907 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
@@ -3,13 +3,14 @@
 
 use libc::{c_char, c_uint};
 
+use super::MetadataKindId;
 use super::ffi::{BasicBlock, Metadata, Module, Type, Value};
 use crate::llvm::Bool;
 
 #[link(name = "llvm-wrapper", kind = "static")]
 unsafe extern "C" {
     // Enzyme
-    pub(crate) fn LLVMRustHasMetadata(I: &Value, KindID: c_uint) -> bool;
+    pub(crate) safe fn LLVMRustHasMetadata(I: &Value, KindID: MetadataKindId) -> bool;
     pub(crate) fn LLVMRustEraseInstUntilInclusive(BB: &BasicBlock, I: &Value);
     pub(crate) fn LLVMRustGetLastInstruction<'a>(BB: &BasicBlock) -> Option<&'a Value>;
     pub(crate) fn LLVMRustDIGetInstMetadata(I: &Value) -> Option<&Metadata>;
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index e3d0b928c97..39087a4d6f4 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -976,6 +976,16 @@ pub type SelfProfileAfterPassCallback = unsafe extern "C" fn(*mut c_void);
 pub type GetSymbolsCallback = unsafe extern "C" fn(*mut c_void, *const c_char) -> *mut c_void;
 pub type GetSymbolsErrorCallback = unsafe extern "C" fn(*const c_char) -> *mut c_void;
 
+#[derive(Copy, Clone)]
+#[repr(transparent)]
+pub struct MetadataKindId(c_uint);
+
+impl From<MetadataType> for MetadataKindId {
+    fn from(value: MetadataType) -> Self {
+        Self(value as c_uint)
+    }
+}
+
 unsafe extern "C" {
     // Create and destroy contexts.
     pub(crate) fn LLVMContextDispose(C: &'static mut Context);
@@ -983,7 +993,7 @@ unsafe extern "C" {
         C: &Context,
         Name: *const c_char,
         SLen: c_uint,
-    ) -> c_uint;
+    ) -> MetadataKindId;
 
     // Create modules.
     pub(crate) fn LLVMModuleCreateWithNameInContext(
@@ -1050,9 +1060,9 @@ unsafe extern "C" {
     pub(crate) fn LLVMGetValueName2(Val: &Value, Length: *mut size_t) -> *const c_char;
     pub(crate) fn LLVMSetValueName2(Val: &Value, Name: *const c_char, NameLen: size_t);
     pub(crate) fn LLVMReplaceAllUsesWith<'a>(OldVal: &'a Value, NewVal: &'a Value);
-    pub(crate) fn LLVMSetMetadata<'a>(Val: &'a Value, KindID: c_uint, Node: &'a Value);
+    pub(crate) safe fn LLVMSetMetadata<'a>(Val: &'a Value, KindID: MetadataKindId, Node: &'a Value);
     pub(crate) fn LLVMGlobalSetMetadata<'a>(Val: &'a Value, KindID: c_uint, Metadata: &'a Metadata);
-    pub(crate) fn LLVMValueAsMetadata(Node: &Value) -> &Metadata;
+    pub(crate) safe fn LLVMValueAsMetadata(Node: &Value) -> &Metadata;
 
     // Operations on constants of any type
     pub(crate) fn LLVMConstNull(Ty: &Type) -> &Value;
@@ -1146,7 +1156,7 @@ unsafe extern "C" {
     pub(crate) fn LLVMSetThreadLocalMode(GlobalVar: &Value, Mode: ThreadLocalMode);
     pub(crate) fn LLVMIsGlobalConstant(GlobalVar: &Value) -> Bool;
     pub(crate) fn LLVMSetGlobalConstant(GlobalVar: &Value, IsConstant: Bool);
-    pub(crate) fn LLVMSetTailCall(CallInst: &Value, IsTailCall: Bool);
+    pub(crate) safe fn LLVMSetTailCall(CallInst: &Value, IsTailCall: Bool);
 
     // Operations on attributes
     pub(crate) fn LLVMCreateStringAttribute(
@@ -1203,7 +1213,7 @@ unsafe extern "C" {
     pub(crate) fn LLVMGetCurrentDebugLocation2<'a>(Builder: &Builder<'a>) -> Option<&'a Metadata>;
 
     // Terminators
-    pub(crate) fn LLVMBuildRetVoid<'a>(B: &Builder<'a>) -> &'a Value;
+    pub(crate) safe fn LLVMBuildRetVoid<'a>(B: &Builder<'a>) -> &'a Value;
     pub(crate) fn LLVMBuildRet<'a>(B: &Builder<'a>, V: &'a Value) -> &'a Value;
     pub(crate) fn LLVMBuildBr<'a>(B: &Builder<'a>, Dest: &'a BasicBlock) -> &'a Value;
     pub(crate) fn LLVMBuildCondBr<'a>(
@@ -1679,7 +1689,7 @@ unsafe extern "C" {
         Packed: Bool,
     );
 
-    pub(crate) fn LLVMMetadataAsValue<'a>(C: &'a Context, MD: &'a Metadata) -> &'a Value;
+    pub(crate) safe fn LLVMMetadataAsValue<'a>(C: &'a Context, MD: &'a Metadata) -> &'a Value;
 
     pub(crate) fn LLVMSetUnnamedAddress(Global: &Value, UnnamedAddr: UnnamedAddr);