Auto merge of #83260 - durin42:llvm-update, r=nagisa

rustc: changes to allow an llvm update

This lets LLVM be built using 2b5f3f446f36, which is only a few weeks old. The next change in LLVM (5de2d189e6ad) breaks rustc again by removing a function that's exposed into the Rust code, but I'll file a bug about that separately.

Please scrutinize the `thinLTOResolvePrevailingInIndex` call, as I'm not at all sure an empty config is right.

I'm also suspicious that a specific alignment could be specified in the call to CreateAtomicCmpXchg, but I don't know enough to figure that out.

Thanks!

1 files changed, 9 insertions, 0 deletions

diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index a8536595404..0391feaf499 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -382,9 +382,18 @@ LLVMRustBuildAtomicCmpXchg(LLVMBuilderRef B, LLVMValueRef Target,
                            LLVMValueRef Old, LLVMValueRef Source,
                            LLVMAtomicOrdering Order,
                            LLVMAtomicOrdering FailureOrder, LLVMBool Weak) {
+#if LLVM_VERSION_GE(13,0)
+  // Rust probably knows the alignment of the target value and should be able to
+  // specify something more precise than MaybeAlign here. See also
+  // https://reviews.llvm.org/D97224 which may be a useful reference.
+  AtomicCmpXchgInst *ACXI = unwrap(B)->CreateAtomicCmpXchg(
+      unwrap(Target), unwrap(Old), unwrap(Source), llvm::MaybeAlign(), fromRust(Order),
+      fromRust(FailureOrder));
+#else
   AtomicCmpXchgInst *ACXI = unwrap(B)->CreateAtomicCmpXchg(
       unwrap(Target), unwrap(Old), unwrap(Source), fromRust(Order),
       fromRust(FailureOrder));
+#endif
   ACXI->setWeak(Weak);
   return wrap(ACXI);
 }