[llvm] [RISCV] Prevent RISCVMergeBaseOffsetOpt from calling getVRegDef on a physical register. (PR #78762)

[Alex Bradbury via llvm-commits]

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@@ -964,3 +964,69 @@ for.body:                                         ; preds = %for.body.lr.ph, %fo
 }
 
 declare void @f(ptr)
+
+ at g = external dso_local global [100 x [100 x i8]]
+
+; This Test used to crash due to caling getVRegDef on X0.
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asb wrote:

Nit: Test => test, and caling => calling
(Sorry!)

https://github.com/llvm/llvm-project/pull/78762