[llvm] [Xtensa] Implement support for the BranchRelaxation. (PR #113450)

[Matt Arsenault via llvm-commits]

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@@ -255,19 +256,42 @@ void XtensaFrameLowering::determineCalleeSaves(MachineFunction &MF,
     SavedRegs.set(FP);
 }
 
+static unsigned estimateFunctionSizeInBytes(const MachineFunction &MF,
+                                            const XtensaInstrInfo &TII) {
+  unsigned FnSize = 0;
+  for (auto &MBB : MF) {
+    for (auto &MI : MBB) {
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arsenm wrote:

Account for block (and function) alignment? 

https://github.com/llvm/llvm-project/pull/113450