[llvm] [amdgpu] Add llvm.amdgcn.init.whole.wave intrinsic (PR #105822)

[Matt Arsenault via llvm-commits]

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@@ -575,6 +575,14 @@ def SI_INIT_EXEC_FROM_INPUT : SPseudoInstSI <
   let Defs = [EXEC];
 }
 
+// Sets EXEC to all lanes and returns the previous EXEC.
+def SI_INIT_WHOLE_WAVE : SPseudoInstSI <
+  (outs SReg_1:$dst), (ins),
+  [(set i1:$dst, (int_amdgcn_init_whole_wave))]> {
+  let Defs = [EXEC];
+  let Uses = [EXEC];
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arsenm wrote:

isConvergent = true? 

https://github.com/llvm/llvm-project/pull/105822