[llvm] [TTI] getScalingFactorCost should return InstructionCost::getInvalid() instead of -1. (PR #129802)

[David Sherwood via llvm-commits]

================
@@ -364,7 +364,7 @@ class TargetTransformInfoImplBase {
                               Scale, AddrSpace, /*I=*/nullptr,
                               BaseOffset.getScalable()))
       return 0;
-    return -1;
+    return InstructionCost::getInvalid();
----------------
david-arm wrote:

Ah I see. That's fine then, and I guess since the LSR code asserts the cost is valid at least we should catch any problems.

https://github.com/llvm/llvm-project/pull/129802