[llvm] [llvm][CodeGen] Fix the empty interval issue in Window Scheduler(#128714) (PR #129204)

[Matt Arsenault via llvm-commits]

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@@ -928,6 +948,26 @@ void ModuloScheduleExpander::addBranches(MachineBasicBlock &PreheaderBB,
   }
 }
 
+/// Some registers are generated during the kernel expansion. We calculate the
+/// live intervals of these registers after the expansion.
+void ModuloScheduleExpander::calculateIntervals() {
+  // The interval can be computed if all the register's non-debug users have
+  // slot indexes.
+  auto CanCalculateInterval = [this](Register Reg) -> bool {
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arsenm wrote:

You shouldn't need to pre-filter anything. Your function is broken if there are instructions without slot indexes 

https://github.com/llvm/llvm-project/pull/129204