[llvm] [RISCV] Add missing check before accessing pointer (PR #121816)

[Philip Reames via llvm-commits]

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@@ -320,6 +320,18 @@ define i64 @add_shl_moreOneUse_sh3add(i64 %x) {
   ret i64 %add
 }
 
+define i64 @add_shl_sext(ptr %0, i32 %1) {
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preames wrote:

Add a comment of the form
;; Covers a case which previously crashed (prXXXXX)

https://github.com/llvm/llvm-project/pull/121816