[llvm] [LV][NFC] Factor out MinBWs of values from the cost model (PR #194492)

[David Sherwood via llvm-commits]

================
@@ -5507,10 +5495,10 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I,
       [[maybe_unused]] Instruction *Op0AsInstruction =
           dyn_cast<Instruction>(I->getOperand(0));
       assert((!canTruncateToMinimalBitwidth(Op0AsInstruction, VF) ||
-              MinBWs[I] == MinBWs[Op0AsInstruction]) &&
+              InstrMinBWs == MinBWs.lookup(Op0AsInstruction)) &&
----------------
david-arm wrote:

OK fair enough! I guess the `const` adds extra protection to avoid accidental modification.

https://github.com/llvm/llvm-project/pull/194492