[llvm] [TableGen] Inherit properties from the nearest allocatable superclass. (PR #127018)

[Pete Chou via llvm-commits]

================
@@ -861,23 +861,27 @@ CodeGenRegisterClass::CodeGenRegisterClass(CodeGenRegBank &RegBank,
   }
 }
 
-// Compute inherited propertied for a synthesized register class.
+// Compute inherited properties for a synthesized register class.
 void CodeGenRegisterClass::inheritProperties(CodeGenRegBank &RegBank) {
   assert(!getDef() && "Only synthesized classes can inherit properties");
   assert(!SuperClasses.empty() && "Synthesized class without super class");
 
-  // The last super-class is the smallest one.
-  CodeGenRegisterClass &Super = *SuperClasses.back();
+  // The last super-class is the smallest one in topological order. Check for
+  // allocatable super-classes and inherit from the nearest allocatable one if
+  // any.
+  auto NearestAllocSCRIt = std::find_if(
+      SuperClasses.rbegin(), SuperClasses.rend(),
+      [&](const CodeGenRegisterClass *S) { return S->Allocatable; });
----------------
petechou wrote:

Thanks for your suggestion. Update to use llvm::find_if with reverse as we want to find the last occurrence.

https://github.com/llvm/llvm-project/pull/127018