The metatype operand on AllocRefDynamicInst is not always at index 1, use getNumTailTypes()

Author: kubamracek

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyAllocRefDynamic.swift

@@ -26,9 +26,9 @@ extension AllocRefDynamicInst : OnoneSimplifyable {
     ///   %8 = (... some use of ...) %7 : $BaseClass
 
     let type: Type
-    if let metatypeInst = operands[1].value as? MetatypeInst {
+    if let metatypeInst = metatypeOperand.value as? MetatypeInst {
       type = metatypeInst.type.loweredInstanceTypeOfMetatype(in: parentFunction)
-    } else if let upcastInst = operands[1].value as? UpcastInst,
+    } else if let upcastInst = metatypeOperand.value as? UpcastInst,
         let metatypeInst = upcastInst.operands[0].value as? MetatypeInst {
       type = metatypeInst.type.loweredInstanceTypeOfMetatype(in: parentFunction)
     } else {

SwiftCompilerSources/Sources/SIL/Instruction.swift

@@ -1196,6 +1196,11 @@ final public class AllocRefDynamicInst : AllocRefInstBase {
   public var isDynamicTypeDeinitAndSizeKnownEquivalentToBaseType: Bool {
     bridged.AllocRefDynamicInst_isDynamicTypeDeinitAndSizeKnownEquivalentToBaseType()
   }
+
+  public var metatypeOperand: Operand {
+    let numTailTypes = bridged.AllocRefInstBase_getNumTailTypes()
+    return operands[numTailTypes]
+  }
 }
 
 final public class AllocBoxInst : SingleValueInstruction, Allocation, DebugVariableInstruction {