Tell LLVM about read-only captures

`&Freeze` parameters are not only `readonly` within the function,
but any captures of the pointer can also only be used for reads.
This can now be encoded using the `captures(address, read_provenance)`
attribute.

1 files changed, 8 insertions, 0 deletions

diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index e4fe1fc2e42..e699e4b9c13 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -278,6 +278,7 @@ enum class LLVMRustAttributeKind {
   Writable = 42,
   DeadOnUnwind = 43,
   DeadOnReturn = 44,
+  CapturesReadOnly = 45,
 };
 
 static Attribute::AttrKind fromRust(LLVMRustAttributeKind Kind) {
@@ -376,6 +377,8 @@ static Attribute::AttrKind fromRust(LLVMRustAttributeKind Kind) {
 #else
     report_fatal_error("DeadOnReturn attribute requires LLVM 21 or later");
 #endif
+  case LLVMRustAttributeKind::CapturesReadOnly:
+    report_fatal_error("Should be handled separately");
   }
   report_fatal_error("bad LLVMRustAttributeKind");
 }
@@ -430,6 +433,11 @@ LLVMRustCreateAttrNoValue(LLVMContextRef C, LLVMRustAttributeKind RustAttr) {
   if (RustAttr == LLVMRustAttributeKind::NoCapture) {
     return wrap(Attribute::getWithCaptureInfo(*unwrap(C), CaptureInfo::none()));
   }
+  if (RustAttr == LLVMRustAttributeKind::CapturesReadOnly) {
+    return wrap(Attribute::getWithCaptureInfo(
+        *unwrap(C), CaptureInfo(CaptureComponents::Address |
+                                CaptureComponents::ReadProvenance)));
+  }
 #endif
   return wrap(Attribute::get(*unwrap(C), fromRust(RustAttr)));
 }