Rollup merge of #145420 - Zalathar:llvm-c, r=WaffleLapkin

cg_llvm: Use LLVM-C bindings for `LLVMSetTailCallKind`, `LLVMGetTypeKind`

This PR replaces two existing `LLVMRust` bindings with equivalent calls to the LLVM-C API.

For `LLVMGetTypeKind`, we avoid the UB hazard by declaring the foreign function to return `RawEnum<TypeKind>` (which is a wrapper around `u32`), and then perform checked conversion from `u32` to `TypeKind`.

Author: Zalathar

compiler/rustc_codegen_llvm/src/builder.rs

@@ -1453,7 +1453,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         instance: Option<Instance<'tcx>>,
     ) {
         let call = self.call(llty, fn_attrs, Some(fn_abi), llfn, args, funclet, instance);
-        llvm::LLVMRustSetTailCallKind(call, llvm::TailCallKind::MustTail);
+        llvm::LLVMSetTailCallKind(call, llvm::TailCallKind::MustTail);
 
         match &fn_abi.ret.mode {
             PassMode::Ignore | PassMode::Indirect { .. } => self.ret_void(),

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -97,6 +97,7 @@ pub(crate) enum ModuleFlagMergeBehavior {
 
 // Consts for the LLVM CallConv type, pre-cast to usize.
 
+/// Must match the layout of `LLVMTailCallKind`.
 #[derive(Copy, Clone, PartialEq, Debug)]
 #[repr(C)]
 #[allow(dead_code)]
@@ -332,10 +333,15 @@ impl RealPredicate {
     }
 }
 
-/// LLVMTypeKind
-#[derive(Copy, Clone, PartialEq, Debug)]
+/// Must match the layout of `LLVMTypeKind`.
+///
+/// Use [`RawEnum<TypeKind>`] for values of `LLVMTypeKind` returned from LLVM,
+/// to avoid risk of UB if LLVM adds new enum values.
+///
+/// All of LLVM's variants should be declared here, even if no Rust-side code refers
+/// to them, because unknown variants will cause [`RawEnum::to_rust`] to panic.
+#[derive(Copy, Clone, PartialEq, Debug, TryFromU32)]
 #[repr(C)]
-#[expect(dead_code, reason = "Some variants are unused, but are kept to match LLVM-C")]
 pub(crate) enum TypeKind {
     Void = 0,
     Half = 1,
@@ -1046,6 +1052,8 @@ unsafe extern "C" {
         CanThrow: llvm::Bool,
     ) -> &'ll Value;
 
+    pub(crate) safe fn LLVMGetTypeKind(Ty: &Type) -> RawEnum<TypeKind>;
+
     // Operations on integer types
     pub(crate) fn LLVMInt1TypeInContext(C: &Context) -> &Type;
     pub(crate) fn LLVMInt8TypeInContext(C: &Context) -> &Type;
@@ -1197,7 +1205,7 @@ unsafe extern "C" {
     pub(crate) safe fn LLVMIsGlobalConstant(GlobalVar: &Value) -> Bool;
     pub(crate) safe fn LLVMSetGlobalConstant(GlobalVar: &Value, IsConstant: Bool);
     pub(crate) safe fn LLVMSetTailCall(CallInst: &Value, IsTailCall: Bool);
-    pub(crate) safe fn LLVMRustSetTailCallKind(CallInst: &Value, Kind: TailCallKind);
+    pub(crate) safe fn LLVMSetTailCallKind(CallInst: &Value, kind: TailCallKind);
 
     // Operations on attributes
     pub(crate) fn LLVMCreateStringAttribute(
@@ -1841,9 +1849,6 @@ unsafe extern "C" {
     // Create and destroy contexts.
     pub(crate) fn LLVMRustContextCreate(shouldDiscardNames: bool) -> &'static mut Context;
 
-    /// See llvm::LLVMTypeKind::getTypeID.
-    pub(crate) fn LLVMRustGetTypeKind(Ty: &Type) -> TypeKind;
-
     // Operations on all values
     pub(crate) fn LLVMRustGlobalAddMetadata<'a>(
         Val: &'a Value,

compiler/rustc_codegen_llvm/src/type_.rs

@@ -204,7 +204,7 @@ impl<'ll, CX: Borrow<SCx<'ll>>> BaseTypeCodegenMethods for GenericCx<'ll, CX> {
     }
 
     fn type_kind(&self, ty: &'ll Type) -> TypeKind {
-        unsafe { llvm::LLVMRustGetTypeKind(ty).to_generic() }
+        llvm::LLVMGetTypeKind(ty).to_rust().to_generic()
     }
 
     fn type_ptr(&self) -> &'ll Type {

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -1460,60 +1460,6 @@ LLVMRustGetDiagInfoKind(LLVMDiagnosticInfoRef DI) {
   return toRust((DiagnosticKind)unwrap(DI)->getKind());
 }
 
-// This is kept distinct from LLVMGetTypeKind, because when
-// a new type kind is added, the Rust-side enum must be
-// updated or UB will result.
-extern "C" LLVMTypeKind LLVMRustGetTypeKind(LLVMTypeRef Ty) {
-  switch (unwrap(Ty)->getTypeID()) {
-  case Type::VoidTyID:
-    return LLVMVoidTypeKind;
-  case Type::HalfTyID:
-    return LLVMHalfTypeKind;
-  case Type::FloatTyID:
-    return LLVMFloatTypeKind;
-  case Type::DoubleTyID:
-    return LLVMDoubleTypeKind;
-  case Type::X86_FP80TyID:
-    return LLVMX86_FP80TypeKind;
-  case Type::FP128TyID:
-    return LLVMFP128TypeKind;
-  case Type::PPC_FP128TyID:
-    return LLVMPPC_FP128TypeKind;
-  case Type::LabelTyID:
-    return LLVMLabelTypeKind;
-  case Type::MetadataTyID:
-    return LLVMMetadataTypeKind;
-  case Type::IntegerTyID:
-    return LLVMIntegerTypeKind;
-  case Type::FunctionTyID:
-    return LLVMFunctionTypeKind;
-  case Type::StructTyID:
-    return LLVMStructTypeKind;
-  case Type::ArrayTyID:
-    return LLVMArrayTypeKind;
-  case Type::PointerTyID:
-    return LLVMPointerTypeKind;
-  case Type::FixedVectorTyID:
-    return LLVMVectorTypeKind;
-  case Type::TokenTyID:
-    return LLVMTokenTypeKind;
-  case Type::ScalableVectorTyID:
-    return LLVMScalableVectorTypeKind;
-  case Type::BFloatTyID:
-    return LLVMBFloatTypeKind;
-  case Type::X86_AMXTyID:
-    return LLVMX86_AMXTypeKind;
-  default: {
-    std::string error;
-    auto stream = llvm::raw_string_ostream(error);
-    stream << "Rust does not support the TypeID: " << unwrap(Ty)->getTypeID()
-           << " for the type: " << *unwrap(Ty);
-    stream.flush();
-    report_fatal_error(error.c_str());
-  }
-  }
-}
-
 DEFINE_SIMPLE_CONVERSION_FUNCTIONS(SMDiagnostic, LLVMSMDiagnosticRef)
 
 extern "C" LLVMSMDiagnosticRef LLVMRustGetSMDiagnostic(LLVMDiagnosticInfoRef DI,
@@ -1993,29 +1939,3 @@ extern "C" void LLVMRustSetNoSanitizeHWAddress(LLVMValueRef Global) {
   MD.NoHWAddress = true;
   GV.setSanitizerMetadata(MD);
 }
-
-enum class LLVMRustTailCallKind {
-  None = 0,
-  Tail = 1,
-  MustTail = 2,
-  NoTail = 3
-};
-
-extern "C" void LLVMRustSetTailCallKind(LLVMValueRef Call,
-                                        LLVMRustTailCallKind Kind) {
-  CallInst *CI = unwrap<CallInst>(Call);
-  switch (Kind) {
-  case LLVMRustTailCallKind::None:
-    CI->setTailCallKind(CallInst::TCK_None);
-    break;
-  case LLVMRustTailCallKind::Tail:
-    CI->setTailCallKind(CallInst::TCK_Tail);
-    break;
-  case LLVMRustTailCallKind::MustTail:
-    CI->setTailCallKind(CallInst::TCK_MustTail);
-    break;
-  case LLVMRustTailCallKind::NoTail:
-    CI->setTailCallKind(CallInst::TCK_NoTail);
-    break;
-  }
-}