[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);
+    }
+
+    if (!VeneerTargetSymbol)
+      continue;
+
+    for (const MCSymbol *Symbol : BF.getSymbols())
       VeneerDestinations[Symbol] = VeneerTargetSymbol;
+
+    NumEliminatedVeneers++;
+    BF.setPseudo(true);
   }
 
   BC.outs() << "BOLT-INFO: number of removed linker-inserted veneers: "
-            << VeneersCount << "\n";
+            << NumEliminatedVeneers << '\n';
----------------
paschalis-mpeis wrote:

Not directly related, but was there a particular reason the other statistic at [L102](https://github.com/llvm/llvm-project/pull/113408/files#diff-a95d88f57c03d0d140e29f5378e67030fbe79efc675342ec8290ad6aeea22ff7R102) was a debug message?

In case the output is helpful to understand whether the number of eliminated veneers does match or not the number of patched call-sites, we could maybe combine them and emit them both at L102?

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