[clang] [Clang][Driver] Enable internalization by default for AMDGPU (PR #138365)

[Matt Arsenault via cfe-commits]

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@@ -9284,6 +9284,12 @@ void LinkerWrapper::ConstructJob(Compilation &C, const JobAction &JA,
         CmdArgs.push_back(Args.MakeArgString(
             "--device-linker=" + TC->getTripleString() + "=" + Arg));
 
+      // Enable internalization for AMDGPU.
+      if (TC->getTriple().isAMDGPU())
+        CmdArgs.push_back(
+            Args.MakeArgString("--device-linker=" + TC->getTripleString() +
+                               "=-plugin-opt=-amdgpu-internalize-symbols"));
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arsenm wrote:

This looks more like "always" than "by default".

The implementation details are kind of a hack. We should be able to just run the ordinary internalize pass without the special AMDGPU filter. https://github.com/llvm/llvm-project/blob/c63687c04f96e3b1db9ce0f70e5f331fce69959b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp#L761

The most legitimate part of this is the isEntryFunctionCC, which we could just make the internalize pass directly do. The sanitizer name hacks are also obviously hacks.

The attempt to drop constant users looks like a bad side effect a predicate should not have, I don't know what that's doing there

https://github.com/llvm/llvm-project/pull/138365