[llvm] [AIX][TLS] Produce a faster local-exec access sequence for the "aix-small-tls" global variable attribute (PR #83053)

[Kai Nacke via llvm-commits]

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@@ -7573,6 +7573,22 @@ static void reduceVSXSwap(SDNode *N, SelectionDAG *DAG) {
   DAG->ReplaceAllUsesOfValueWith(SDValue(N, 0), N->getOperand(0));
 }
 
+// Check if an SDValue has the 'aix-small-tls' global variable attribute.
+static bool hasAIXSmallTLSAttr(SDValue Val) {
+  GlobalAddressSDNode *GA = dyn_cast<GlobalAddressSDNode>(Val);
+  if (!GA)
+    return false;
+
+  const GlobalVariable *GV = dyn_cast<GlobalVariable>(GA->getGlobal());
+  if (!GV)
+    return false;
+
+  if (!GV->hasAttribute("aix-small-tls"))
+    return false;
+
+  return true;
----------------
redstar wrote:

IMHO you can collapse the lines without loosing readability:
```suggestion
  return GV->hasAttribute("aix-small-tls");
```

https://github.com/llvm/llvm-project/pull/83053