[llvm] [InstCombine] Fold `getelementptr inbounds null, idx -> null` (PR #130742)

[Matt Arsenault via llvm-commits]

================
@@ -383,7 +383,7 @@ bb:
   ret <2 x half> %result
 }
 
-define <2 x half> @chain_hi_to_lo_flat() {
+define <2 x half> @chain_hi_to_lo_flat() null_pointer_is_valid {
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arsenm wrote:

```suggestion
define <2 x half> @chain_hi_to_lo_flat(ptr inreg %ptr) {
```

https://github.com/llvm/llvm-project/pull/130742