Mark pure asm as willreturn

compiler/rustc_codegen_llvm/src/asm.rs

@@ -304,6 +304,7 @@ impl AsmBuilderMethods<'tcx> for Builder<'a, 'll, 'tcx> {
             } else if options.contains(InlineAsmOptions::READONLY) {
                 llvm::Attribute::ReadOnly.apply_callsite(llvm::AttributePlace::Function, result);
             }
+            llvm::Attribute::WillReturn.apply_callsite(llvm::AttributePlace::Function, result);
         } else if options.contains(InlineAsmOptions::NOMEM) {
             llvm::Attribute::InaccessibleMemOnly
                 .apply_callsite(llvm::AttributePlace::Function, result);

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -132,6 +132,7 @@ pub enum Attribute {
     ReadNone = 26,
     InaccessibleMemOnly = 27,
     SanitizeHWAddress = 28,
+    WillReturn = 29,
 }
 
 /// LLVMIntPredicate

compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h

@@ -86,6 +86,7 @@ enum LLVMRustAttribute {
   ReadNone = 26,
   InaccessibleMemOnly = 27,
   SanitizeHWAddress = 28,
+  WillReturn = 29,
 };
 
 typedef struct OpaqueRustString *RustStringRef;

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -207,6 +207,8 @@ static Attribute::AttrKind fromRust(LLVMRustAttribute Kind) {
     return Attribute::InaccessibleMemOnly;
   case SanitizeHWAddress:
     return Attribute::SanitizeHWAddress;
+  case WillReturn:
+    return Attribute::WillReturn;
   }
   report_fatal_error("bad AttributeKind");
 }