[llvm] [yaml2obj][XOFF] Update yaml2obj for XCOFF to create valid XCOFF files in more cases. (PR #77620)

[James Henderson via llvm-commits]

================
@@ -134,23 +144,46 @@ bool XCOFFWriter::initSectionHeader(uint64_t &CurrentOffset) {
       }
     }
 
-    // Calculate the physical/virtual address. This field should contain 0 for
-    // all sections except the text, data and bss sections.
-    if (InitSections[I].Flags != XCOFF::STYP_TEXT &&
-        InitSections[I].Flags != XCOFF::STYP_DATA &&
-        InitSections[I].Flags != XCOFF::STYP_BSS)
-      InitSections[I].Address = 0;
-    else
-      InitSections[I].Address = CurrentSecAddr;
+    if (!InitSections[I].Size)
+      InitSections[I].Size = InitSections[I].SectionData.binary_size();
+
+    // We cannot compute section addresses in general. We only enforce
+    // the rule .data and .bss are consecutive, as are .tdata and .tbss.
+    switch (InitSections[I].Flags) {
+    case XCOFF::STYP_DATA:
+      CurrentDataAddr = InitSections[I].Address + InitSections[I].Size;
+      break;
+    case XCOFF::STYP_BSS:
+      if (!InitSections[I].Address)
+        InitSections[I].Address = CurrentDataAddr;
+      break;
+    case XCOFF::STYP_TDATA:
+      CurrentTDataAddr = InitSections[I].Address + InitSections[I].Size;
+      break;
+    case XCOFF::STYP_TBSS:
+      if (!InitSections[I].Address)
+        InitSections[I].Address = CurrentTDataAddr;
+      break;
+    }
 
-    // Calculate the FileOffsetToData and data size for sections.
     if (InitSections[I].SectionData.binary_size()) {
-      InitSections[I].FileOffsetToData = CurrentOffset;
+      if (InitSections[I].FileOffsetToData) {
+        // Use the providedFileOffsetToData.
+        if (CurrentOffset > InitSections[I].FileOffsetToData) {
+          ErrHandler("Specified FileOffsetToData will overwrite existing data");
+          return false;
+        }
+        CurrentOffset = InitSections[I].FileOffsetToData;
+      } else {
+        CurrentOffset = alignTo(CurrentOffset, DefaultSectionAlign);
+        InitSections[I].FileOffsetToData = CurrentOffset;
+      }
       CurrentOffset += InitSections[I].SectionData.binary_size();
-      // Ensure the offset is aligned to DefaultSectionAlign.
-      CurrentOffset = alignTo(CurrentOffset, DefaultSectionAlign);
-      InitSections[I].Size = CurrentOffset - InitSections[I].FileOffsetToData;
-      CurrentSecAddr += InitSections[I].Size;
+      if (CurrentOffset > MaxRawDataSize) {
+        ErrHandler("maximum object size of" + Twine(MaxRawDataSize) +
+                   "exceeded when writing section data");
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jh7370 wrote:

Could you include the name of the section that is being written?

https://github.com/llvm/llvm-project/pull/77620