[llvm] [NFC][LLVM] Namespace cleanup in DeadStoreElimination (PR #163303)

[Rahul Joshi via llvm-commits]

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@@ -828,7 +828,7 @@ bool isNoopIntrinsic(Instruction *I) {
 }
 
 // Check if we can ignore \p D for DSE.
-bool canSkipDef(MemoryDef *D, bool DefVisibleToCaller) {
+static bool canSkipDef(MemoryDef *D, bool DefVisibleToCaller) {
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jurahul wrote:

To confirm to LLVM CS: https://llvm.org/docs/CodingStandards.html#restrict-visibility 
> Because of this, we have a simple guideline: make anonymous namespaces as small as possible, and only use them for class declarations

https://github.com/llvm/llvm-project/pull/163303