[clang] [llvm] [AMDGPU] Change CF intrinsics lowering to reconverge on predecessors. (PR #92809)

[Matt Arsenault via llvm-commits]

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@@ -15740,6 +15740,32 @@ void SITargetLowering::finalizeLowering(MachineFunction &MF) const {
     }
   }
 
+  // ISel inserts copy to regs for the successor PHIs
+  // at the BB end. We need to move the SI_WAVE_RECONVERGE right before the
+  // branch.
+  for (auto &MBB : MF) {
+    for (auto &MI : MBB) {
+      if (MI.getOpcode() == AMDGPU::SI_WAVE_RECONVERGE) {
+        MachineBasicBlock::iterator I(MI);
+        MachineBasicBlock::iterator Next = std::next(I);
+        bool NeedToMove = false;
+        while (Next != MBB.end() && !Next->isBranch()) {
+          NeedToMove = true;
+          Next++;
+        }
+
+        assert((Next == MBB.end() || !Next->readsRegister(AMDGPU::SCC, TRI)) &&
+               "Malformed CFG detected!\n");
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arsenm wrote:

No newline in the string, this isn't real printing 

https://github.com/llvm/llvm-project/pull/92809