[llvm] [PowerPC] Avoid repeated hash lookups (NFC) (PR #131724)

[Nikita Popov via llvm-commits]

================
@@ -2489,22 +2489,23 @@ bool PPCFrameLowering::spillCalleeSavedRegisters(
         if (Spilled[Dst])
           continue;
 
-        if (VSRContainingGPRs[Dst].second != 0) {
+        auto &VSR = VSRContainingGPRs[Dst];
----------------
nikic wrote:

```suggestion
        const auto &VSR = VSRContainingGPRs[Dst];
```

https://github.com/llvm/llvm-project/pull/131724