[llvm] [AMDGPU] Add live-through register set printing to GCNRegPressurePrinter pass. (PR #71096)

[Valery Pykhtin via llvm-commits]

================
@@ -496,6 +496,34 @@ char &llvm::GCNRegPressurePrinterID = GCNRegPressurePrinter::ID;
 
 INITIALIZE_PASS(GCNRegPressurePrinter, "amdgpu-print-rp", "", true, true)
 
+// Return lanemask of Reg's subregs that are live-through at [Begin, End] and
+// are fully covered by Mask.
+static LaneBitmask
+getRegLiveThroughMask(const MachineRegisterInfo &MRI, const LiveIntervals &LIS,
+                      Register Reg, SlotIndex Begin, SlotIndex End,
+                      LaneBitmask Mask = LaneBitmask::getAll()) {
+
+  auto IsInOneSegment = [Begin, End](const LiveRange &LR) -> bool {
----------------
vpykhtin wrote:

This function checks if start and end slot indexes of a basic block lie within a single segment of a LiveRange thus having a single value, but isLocal seems different:

Comment on isLocal seems misleading to me:
```
    /// True iff this segment is a single segment that lies between the
    /// specified boundaries, exclusively. Vregs live across a backedge are not
    /// considered local. The boundaries are expected to lie within an extended
    /// basic block, so vregs that are not live out should contain no holes.
    bool isLocal(SlotIndex Start, SlotIndex End) const {
      return beginIndex() > Start.getBaseIndex() &&
        endIndex() < End.getBoundaryIndex();
    }
```
This is a member function of LiveRange class and it may contains several segments.
```
    /// beginIndex - Return the lowest numbered slot covered.
    SlotIndex beginIndex() const {
      assert(!empty() && "Call to beginIndex() on empty range.");
      return segments.front().start;
    }

    /// endNumber - return the maximum point of the range of the whole,
    /// exclusive.
    SlotIndex endIndex() const {
      assert(!empty() && "Call to endIndex() on empty range.");
      return segments.back().end;
    }
```




https://github.com/llvm/llvm-project/pull/71096