[clang] [PowerPC] Support local-dynamic TLS relocation on AIX (PR #66316)

[Amy Kwan via cfe-commits]

================
@@ -145,9 +163,88 @@ namespace {
                                                               .addImm(0);
 
         if (IsAIX) {
-          // The variable offset and region handle are copied in r4 and r3. The
-          // copies are followed by GETtlsADDR32AIX/GETtlsADDR64AIX.
-          if (!IsTLSTPRelMI) {
+          if (IsTLSLDAIXMI) {
+            // It is better to put TLSLDAIX node before LoadOffsetToc node,
+            // because LoadOffsetToc node can use clobbers r4/r5. Search for the
+            // first paired LoadOffsetToc node within the same BB.
+            unsigned LDTocOp =
+                Is64Bit ? (IsLargeModel ? PPC::LDtocL : PPC::LDtoc)
+                        : (IsLargeModel ? PPC::LWZtocL : PPC::LWZtoc);
+            MachineBasicBlock::iterator Anchor = I;
+            if (!RegInfo.use_empty(OutReg)) {
+              std::set<MachineInstr *> Uses;
+              // Collect all instructions that use OutReg
+              for (MachineOperand &MO : RegInfo.use_operands(OutReg)) {
+                if (Uses.count(MO.getParent()))
+                  continue;
+                Uses.insert(MO.getParent());
+              }
+              // Find the first Add within current BB.
----------------
amy-kwan wrote:

```suggestion
              // Find the first Add within the current BB.
```

https://github.com/llvm/llvm-project/pull/66316