[GlobalISel] Disable vector types in narrowScalarAddSub

The implementation for vectors is broken and doesn't seem to be used by
anything. Explicitly remove support for them, they can be added again
later when they're properly implemented.

Reviewed By: aemerson

Differential Revision: https://reviews.llvm.org/D95699
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 6ec41c1..fa60913 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -4447,7 +4447,13 @@
   if (TypeIdx != 0)
     return UnableToLegalize;
 
-  uint64_t SizeOp0 = MRI.getType(MI.getOperand(0).getReg()).getSizeInBits();
+  Register DstReg = MI.getOperand(0).getReg();
+  LLT DstType = MRI.getType(DstReg);
+  // FIXME: add support for vector types
+  if (DstType.isVector())
+    return UnableToLegalize;
+
+  uint64_t SizeOp0 = DstType.getSizeInBits();
   uint64_t NarrowSize = NarrowTy.getSizeInBits();
 
   // FIXME: add support for when SizeOp0 isn't an exact multiple of
@@ -4492,12 +4498,7 @@
     DstRegs.push_back(DstReg);
     CarryIn = CarryOut;
   }
-
-  Register DstReg = MI.getOperand(0).getReg();
-  if (MRI.getType(DstReg).isVector())
-    MIRBuilder.buildBuildVector(DstReg, DstRegs);
-  else
-    MIRBuilder.buildMerge(DstReg, DstRegs);
+  MIRBuilder.buildMerge(DstReg, DstRegs);
   MI.eraseFromParent();
   return Legalized;
 }