[llvm] [AMDGPU] Add islands to StructurizeCFG (PR #201675)

[Robert Imschweiler via llvm-commits]

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@@ -7,20 +7,34 @@ define void @callbr_inline_asm(ptr %src, ptr %dst1, ptr %dst2, i32 %c) {
 ; CHECK-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
 ; CHECK-NEXT:    flat_load_dword v0, v[0:1]
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ro-i wrote:

... by introducing isAlreadyStructuredIsland()

https://github.com/llvm/llvm-project/pull/201675