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

[Amy Kwan via cfe-commits]

================
@@ -145,9 +160,78 @@ 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) {
+            // The relative order between the LoadOffset at toc node, and the
+            // ._tls_get_mod node is being tuned here. It is better to put the
+            // LoadOffset at toc node after the call, since the LoadOffset at toc node
+            // can use clobbers r4/r5. Search for the pattern of two Load at toc
+            // nodes, and then move the LoadOffset at toc node right before the
+            // node that uses the OutReg of the ._tls_get_mod node.
----------------
amy-kwan wrote:

```suggestion
            // node that uses the OutReg of the .__tls_get_mod node.
```

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