[llvm] [AIX][TLS] Optimize the small local-exec access sequence for non-zero offsets (PR #71485)

[via llvm-commits]

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@@ -2749,6 +2879,21 @@ bool PPCAIXAsmPrinter::doInitialization(Module &M) {
     Csect->ensureMinAlignment(GOAlign);
   };
 
+  // For all TLS variables, calculate their corresponding addresses and store
+  // them into TLSVarsToAddressMapping, which will be used to determine whether
+  // or not local-exec TLS variables require special assembly printing.
+  uint64_t Address = 0;
+  uint64_t TLSVarAddress = 0;
+  auto DL = M.getDataLayout();
+  for (const auto &G : M.globals()) {
+    if (G.isThreadLocal() && !G.isDeclaration()) {
+      TLSVarAddress = alignTo(Address, getGVAlignment(&G, DL));
+      unsigned GVSize = DL.getTypeAllocSize(G.getValueType());
+      Address = TLSVarAddress + GVSize;
+      TLSVarsToAddressMapping[&G] = TLSVarAddress;
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diggerlin wrote:

I think we do not need a `uint64_t Address = 0;` and `unsigned GVSize`

can we change the code to 

```
 TLSVarAddress = alignTo(TLSVarAddress , getGVAlignment(&G, DL));
 TLSVarsToAddressMapping[&G] = TLSVarAddress;
  TLSVarAddress += DL.getTypeAllocSize(G.getValueType());
```
?

https://github.com/llvm/llvm-project/pull/71485