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

[Qiu Chaofan via llvm-commits]

================
@@ -660,15 +671,17 @@ void PPCAsmPrinter::EmitTlsCall(const MachineInstr *MI,
          "GETtls[ld]ADDR[32] must read GPR3");
 
   if (Subtarget->isAIXABI()) {
-    // On AIX, the variable offset should already be in R4 and the region handle
-    // should already be in R3.
-    // For TLSGD, which currently is the only supported access model, we only
-    // need to generate an absolute branch to .__tls_get_addr.
+    // On AIX, for TLSGD the variable offset should already be in R4 and the
+    // region handle should already be in R3, need to generate an absolute
+    // branch to .__tls_get_addr. For TLSLD the module handle should already be
+    // in R3, need to generate branch to .__tls_get_mod.
----------------
ecnelises wrote:

```suggestion
    // For TLSGD, the variable offset should already be in R4 and the region
    // handle should already be in R3, generate absolute branch to .__tls_get_addr.
    // For TLSLD, the module handle should already be in R3, generate branch
    // to .__tls_get_mod.
```

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