[llvm] [NFC][AMDGPU] Move PhiLoweringHelper and related types into AMDGPU namespace (PR #192586)

[via llvm-commits]

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@@ -29,6 +29,7 @@
 #define DEBUG_TYPE "si-i1-copies"
 
 using namespace llvm;
+using namespace llvm::AMDGPU;
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woruyu wrote:

Thanks for the review. If I remove `using namespace llvm::AMDGPU`; it would require updating more than ~20 call sites to fully qualify the AMDGPU symbols. Is it wroth?

https://github.com/llvm/llvm-project/pull/192586