Check for AutoUpgraded intrinsics, and emit a hard error for unknown intrinsics

Author: sayantn

compiler/rustc_codegen_llvm/src/declare.rs

@@ -177,7 +177,27 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
             fn_abi.apply_attrs_llfn(self, llfn, instance);
         }
 
-        // todo: check for upgrades, and emit error if not upgradable
+        if let FunctionSignature::MaybeInvalidIntrinsic(..) = signature {
+            let mut new_llfn = None;
+            let can_upgrade =
+                unsafe { llvm::LLVMRustUpgradeIntrinsicFunction(llfn, &mut new_llfn, false) };
+
+            if can_upgrade {
+                // not all intrinsics are upgraded to some other intrinsics, most are upgraded to instruction sequences
+                if let Some(new_llfn) = new_llfn {
+                    self.tcx.dcx().note(format!(
+                        "Using deprecated intrinsic `{name}`, `{}` can be used instead",
+                        str::from_utf8(llvm::get_value_name(new_llfn)).unwrap()
+                    ));
+                } else if self.tcx.sess.opts.verbose {
+                    self.tcx.dcx().note(format!(
+                        "Using deprecated intrinsic `{name}`, consider using other intrinsics/instructions"
+                    ));
+                }
+            } else {
+                self.tcx.dcx().fatal(format!("Invalid LLVM intrinsic: `{name}`"))
+            }
+        }
 
         if self.tcx.sess.is_sanitizer_cfi_enabled() {
             if let Some(instance) = instance {

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1195,6 +1195,8 @@ unsafe extern "C" {
 
     // Operations on functions
     pub(crate) fn LLVMSetFunctionCallConv(Fn: &Value, CC: c_uint);
+
+    // Operations about llvm intrinsics
     pub(crate) fn LLVMLookupIntrinsicID(Name: *const c_char, NameLen: size_t) -> c_uint;
     pub(crate) fn LLVMIntrinsicGetType<'a>(
         C: &'a Context,
@@ -1203,6 +1205,11 @@ unsafe extern "C" {
         ParamCount: size_t,
     ) -> &'a Type;
     pub(crate) fn LLVMIntrinsicIsOverloaded(ID: c_uint) -> Bool;
+    pub(crate) fn LLVMRustUpgradeIntrinsicFunction<'a>(
+        Fn: &'a Value,
+        NewFn: &mut Option<&'a Value>,
+        CanUpgradeDebugIntrinsicsToRecords: bool,
+    ) -> bool;
 
     // Operations on parameters
     pub(crate) fn LLVMIsAArgument(Val: &Value) -> Option<&Value>;

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -9,6 +9,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/Magic.h"
 #include "llvm/Bitcode/BitcodeWriter.h"
+#include "llvm/IR/AutoUpgrade.h"
 #include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DiagnosticHandler.h"
@@ -1901,6 +1902,17 @@ extern "C" void LLVMRustGetMangledName(LLVMValueRef V, RustStringRef Str) {
   Mangler().getNameWithPrefix(OS, GV, true);
 }
 
+extern "C" bool
+LLVMRustUpgradeIntrinsicFunction(LLVMValueRef Fn, LLVMValueRef *NewFn,
+                                 bool canUpgradeDebugIntrinsicsToRecords) {
+  Function *F = unwrap<Function>(Fn);
+  Function *NewF = nullptr;
+  bool CanUpgrade =
+      UpgradeIntrinsicFunction(F, NewF, canUpgradeDebugIntrinsicsToRecords);
+  *NewFn = wrap(NewF);
+  return CanUpgrade;
+}
+
 extern "C" int32_t LLVMRustGetElementTypeArgIndex(LLVMValueRef CallSite) {
   auto *CB = unwrap<CallBase>(CallSite);
   switch (CB->getIntrinsicID()) {