[llvm] [BOLT][AArch64] Add support for long absolute LLD thunks/veneers (PR #113408)

[Paschalis Mpeis via llvm-commits]

================
@@ -29,30 +29,47 @@ static llvm::cl::opt<bool>
 namespace llvm {
 namespace bolt {
 
+static bool isPossibleVeneer(const BinaryFunction &BF) {
+  return BF.isAArch64Veneer() || BF.getOneName().starts_with("__AArch64");
+}
+
 Error VeneerElimination::runOnFunctions(BinaryContext &BC) {
   if (!opts::EliminateVeneers || !BC.isAArch64())
     return Error::success();
 
-  std::map<uint64_t, BinaryFunction> &BFs = BC.getBinaryFunctions();
   std::unordered_map<const MCSymbol *, const MCSymbol *> VeneerDestinations;
-  uint64_t VeneersCount = 0;
-  for (auto &It : BFs) {
-    BinaryFunction &VeneerFunction = It.second;
-    if (!VeneerFunction.isAArch64Veneer())
+  uint64_t NumEliminatedVeneers = 0;
+  for (BinaryFunction &BF : llvm::make_second_range(BC.getBinaryFunctions())) {
+    if (!isPossibleVeneer(BF))
       continue;
 
-    VeneersCount++;
-    VeneerFunction.setPseudo(true);
-    MCInst &FirstInstruction = *(VeneerFunction.begin()->begin());
-    const MCSymbol *VeneerTargetSymbol =
-        BC.MIB->getTargetSymbol(FirstInstruction, 1);
-    assert(VeneerTargetSymbol && "Expecting target symbol for instruction");
-    for (const MCSymbol *Symbol : VeneerFunction.getSymbols())
+    if (BF.isIgnored())
+      continue;
+
+    const MCSymbol *VeneerTargetSymbol = 0;
+    uint64_t TargetAddress;
+    if (BC.MIB->matchAbsLongVeneer(BF, TargetAddress)) {
+      if (BinaryFunction *TargetBF =
+              BC.getBinaryFunctionAtAddress(TargetAddress))
+        VeneerTargetSymbol = TargetBF->getSymbol();
+    } else {
+      MCInst &FirstInstruction = *(BF.begin()->begin());
+      if (BC.MIB->hasAnnotation(FirstInstruction, "AArch64Veneer"))
+        VeneerTargetSymbol = BC.MIB->getTargetSymbol(FirstInstruction, 1);
----------------
paschalis-mpeis wrote:

Maybe we could keep the assertion just for the else case?

```cpp
assert(VeneerTargetSymbol && "Expecting target symbol for instruction");
```

https://github.com/llvm/llvm-project/pull/113408