[llvm] [AMDGPU] SCC live interval must be recomputed after CF lowering (PR #81817)

[Matt Arsenault via llvm-commits]

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@@ -951,6 +945,11 @@ bool SILowerControlFlow::runOnMachineFunction(MachineFunction &MF) {
   optimizeEndCf();
 
   if (LIS) {
+    if (Changed) {
+      // These will need to be recomputed for insertions and removals.
+      LIS->removeAllRegUnitsForPhysReg(AMDGPU::EXEC);
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arsenm wrote:

exec is reserved and has no liveness tracking, not sure why it was handled before 

https://github.com/llvm/llvm-project/pull/81817