From f653d3ab30d4cab73af560f39b448ece2a49ff6c Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov@redhat.com>
Date: Tue, 19 Jul 2022 15:03:39 +0200
Subject: [PATCH] Add elementtype attributes for llvm.arm.ldrex/strex
 intrinsics

These intrinsics (and a few more, but there are the only ones
exposed by stdarch) require an elementtype attribute in LLVM 15.
---
 compiler/rustc_codegen_llvm/src/abi.rs        | 16 ++++++++++++++
 compiler/rustc_codegen_llvm/src/llvm/ffi.rs   |  3 +++
 .../rustc_llvm/llvm-wrapper/RustWrapper.cpp   | 22 +++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index d4437bd449d..9eb3574e77b 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -569,6 +569,22 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                 &[cmse_nonsecure_call],
             );
         }
+
+        // Some intrinsics require that an elementtype attribute (with the pointee type of a
+        // pointer argument) is added to the callsite.
+        let element_type_index = unsafe { llvm::LLVMRustGetElementTypeArgIndex(callsite) };
+        if element_type_index >= 0 {
+            let arg_ty = self.args[element_type_index as usize].layout.ty;
+            let pointee_ty = arg_ty.builtin_deref(true).expect("Must be pointer argument").ty;
+            let element_type_attr = unsafe {
+                llvm::LLVMRustCreateElementTypeAttr(bx.llcx, bx.layout_of(pointee_ty).llvm_type(bx))
+            };
+            attributes::apply_to_callsite(
+                callsite,
+                llvm::AttributePlace::Argument(element_type_index as u32),
+                &[element_type_attr],
+            );
+        }
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 9ee6d39fdc9..3139f93bfef 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -1192,6 +1192,7 @@ extern "C" {
     pub fn LLVMRustCreateDereferenceableOrNullAttr(C: &Context, bytes: u64) -> &Attribute;
     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 LLVMRustCreateElementTypeAttr<'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;
@@ -2541,4 +2542,6 @@ extern "C" {
 
     #[allow(improper_ctypes)]
     pub fn LLVMRustGetMangledName(V: &Value, out: &RustString);
+
+    pub fn LLVMRustGetElementTypeArgIndex(CallSite: &Value) -> i32;
 }
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index ef1a65488e2..c333738ded4 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -6,6 +6,7 @@
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/IntrinsicsARM.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/Object/Archive.h"
 #include "llvm/Object/COFFImportFile.h"
@@ -300,6 +301,14 @@ extern "C" LLVMAttributeRef LLVMRustCreateStructRetAttr(LLVMContextRef C, LLVMTy
   return wrap(Attribute::getWithStructRetType(*unwrap(C), unwrap(Ty)));
 }
 
+extern "C" LLVMAttributeRef LLVMRustCreateElementTypeAttr(LLVMContextRef C, LLVMTypeRef Ty) {
+#if LLVM_VERSION_GE(15, 0)
+  return wrap(Attribute::get(*unwrap(C), Attribute::ElementType, unwrap(Ty)));
+#else
+  report_fatal_error("Should not be needed on LLVM < 15");
+#endif
+}
+
 extern "C" LLVMAttributeRef LLVMRustCreateUWTableAttr(LLVMContextRef C, bool Async) {
 #if LLVM_VERSION_LT(15, 0)
   return wrap(Attribute::get(*unwrap(C), Attribute::UWTable));
@@ -1943,3 +1952,16 @@ extern "C" LLVMValueRef LLVMGetAggregateElement(LLVMValueRef C, unsigned Idx) {
     return wrap(unwrap<Constant>(C)->getAggregateElement(Idx));
 }
 #endif
+
+extern "C" int32_t LLVMRustGetElementTypeArgIndex(LLVMValueRef CallSite) {
+#if LLVM_VERSION_GE(15, 0)
+    auto *CB = unwrap<CallBase>(CallSite);
+    switch (CB->getIntrinsicID()) {
+        case Intrinsic::arm_ldrex:
+            return 0;
+        case Intrinsic::arm_strex:
+            return 1;
+    }
+#endif
+    return -1;
+}