[llvm] [AMDGPU] New intrinsic llvm.amdgcn.pops.exiting.wave.id (PR #89612)

[Jay Foad via llvm-commits]

================
@@ -1865,6 +1870,12 @@ let SubtargetPredicate = isNotGFX9Plus in {
 def : GetFPModePat<fpmode_mask_gfx6plus>;
 }
 
+let SubtargetPredicate = isGFX9GFX10 in
+def : GCNPat<
+  (int_amdgcn_pops_exiting_wave_id),
+  (S_MOV_B32_sideeffects (i32 SRC_POPS_EXITING_WAVE_ID))
----------------
jayfoad wrote:

> Is this supposed to act more like readcyclecounter?

Yes. It's a volatile value that can change at any time, even without an explicit write in the IR.

https://github.com/llvm/llvm-project/pull/89612