[clang] [llvm] [AVR] Handle flash RO data mapped to data space for newer devices (PR #146244)

[Patryk Wychowaniec via llvm-commits]

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@@ -263,11 +263,17 @@ bool AVRAsmPrinter::doFinalization(Module &M) {
     auto *Section = cast<MCSectionELF>(TLOF.SectionForGlobal(&GO, TM));
     if (Section->getName().starts_with(".data"))
       NeedsCopyData = true;
-    else if (Section->getName().starts_with(".rodata") && SubTM->hasLPM())
+    else if (Section->getName().starts_with(".rodata") && SubTM->hasLPM()) {
       // AVRs that have a separate program memory (that's most AVRs) store
-      // .rodata sections in RAM.
-      NeedsCopyData = true;
-    else if (Section->getName().starts_with(".bss"))
+      // .rodata sections in RAM,
+      // but XMEGA3 family maps all flash in the data space.
+      // Invoking __do_copy_data with 0 bytes to copy will crash,
+      // so we let the loader handle this for newer devices.
+      if (!(SubTM->hasFeatureSetFamilyXMEGA2() ||
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Patryk27 wrote:

Could we check for `FeatureFLMAP` in here instead?

Feels like that's what it is supposed to do eventually, but we use family as a proxy for the actual flag we're interested in.

https://github.com/llvm/llvm-project/pull/146244