[llvm] [AMDGPU][SplitModule] Do not create empty modules (PR #135761)

[Shilei Tian via llvm-commits]

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@@ -1487,6 +1491,13 @@ static void splitAMDGPUModule(
     for (unsigned NodeID : (*Proposal)[PID].set_bits())
       FnsInPart.insert(&SG.getNode(NodeID).getFunction());
 
+    // Don't create empty module, except for PID 0 because
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shiltian wrote:

because?

https://github.com/llvm/llvm-project/pull/135761