[AIX] Support per global code model. (#79202)

Exploit the per global code model attribute on AIX. On AIX we need to
update both the code sequence used to access the global (either 1 or 2
instructions for small and large code model respectively) and the
storage mapping class that we emit the toc entry.

---------

Co-authored-by: Amy Kwan <akwan0907@gmail.com>

1 files changed, 26 insertions, 13 deletions

diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 6943ce2..15b5942 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -2680,21 +2680,34 @@ MCSection *TargetLoweringObjectFileXCOFF::getSectionForFunctionDescriptor(
 
 MCSection *TargetLoweringObjectFileXCOFF::getSectionForTOCEntry(
     const MCSymbol *Sym, const TargetMachine &TM) const {
-  // Use TE storage-mapping class when large code model is enabled so that
-  // the chance of needing -bbigtoc is decreased. Also, the toc-entry for
-  // EH info is never referenced directly using instructions so it can be
-  // allocated with TE storage-mapping class.
-  // The "_$TLSML" symbol for TLS local-dynamic mode requires XMC_TC, otherwise
-  // the AIX assembler will complain.
+  const XCOFF::StorageMappingClass SMC = [](const MCSymbol *Sym,
+                                            const TargetMachine &TM) {
+    const MCSymbolXCOFF *XSym = cast<MCSymbolXCOFF>(Sym);
+
+    // The "_$TLSML" symbol for TLS local-dynamic mode requires XMC_TC,
+    // otherwise the AIX assembler will complain.
+    if (XSym->getSymbolTableName() == "_$TLSML")
+      return XCOFF::XMC_TC;
+
+    // Use large code model toc entries for ehinfo symbols as they are
+    // never referenced directly. The runtime loads their TOC entry
+    // addresses from the trace-back table.
+    if (XSym->isEHInfo())
+      return XCOFF::XMC_TE;
+
+    // If the symbol does not have a code model specified use the module value.
+    if (!XSym->hasPerSymbolCodeModel())
+      return TM.getCodeModel() == CodeModel::Large ? XCOFF::XMC_TE
+                                                   : XCOFF::XMC_TC;
+
+    return XSym->getPerSymbolCodeModel() == MCSymbolXCOFF::CM_Large
+               ? XCOFF::XMC_TE
+               : XCOFF::XMC_TC;
+  }(Sym, TM);
+
   return getContext().getXCOFFSection(
       cast<MCSymbolXCOFF>(Sym)->getSymbolTableName(), SectionKind::getData(),
-      XCOFF::CsectProperties(
-          ((TM.getCodeModel() == CodeModel::Large &&
-            cast<MCSymbolXCOFF>(Sym)->getSymbolTableName() != "_$TLSML") ||
-           cast<MCSymbolXCOFF>(Sym)->isEHInfo())
-              ? XCOFF::XMC_TE
-              : XCOFF::XMC_TC,
-          XCOFF::XTY_SD));
+      XCOFF::CsectProperties(SMC, XCOFF::XTY_SD));
 }
 
 MCSection *TargetLoweringObjectFileXCOFF::getSectionForLSDA(