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

[James Henderson via llvm-commits]

================
@@ -134,23 +155,58 @@ 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();
+
+    // Section data addresses (physical/virtual) are related to symbol
+    // addresses and alignments. Furthermore, it is possible to specify the
+    // same starting addresses for the .text, .data, and .tdata sections.
+    // Without examining all the symbols and their addreses and alignments,
+    // it is not possible to compute valid section addresses. The only
+    // condition required by XCOFF is that the .bss section immediately
+    // follows the .data section, and the .tbss section immediately follows
+    // the .tdata section. Therefore, we only assign addresses to the .bss
+    // and .tbss sections if they do not already have non-zero addresses.
+    // (If the YAML file is being used to generate a valid object file, we
+    // expect all section addresses to be specified explicitly.)
+    switch (InitSections[I].Flags) {
+    case XCOFF::STYP_DATA:
+      CurrentEndDataAddr = InitSections[I].Address + InitSections[I].Size;
+      break;
+    case XCOFF::STYP_BSS:
+      if (!InitSections[I].Address)
+        InitSections[I].Address = CurrentEndDataAddr;
+      break;
+    case XCOFF::STYP_TDATA:
+      CurrentEndTDataAddr = InitSections[I].Address + InitSections[I].Size;
+      break;
+    case XCOFF::STYP_TBSS:
+      if (!InitSections[I].Address)
+        InitSections[I].Address = CurrentEndTDataAddr;
+      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) {
+          ErrOverwrite(CurrentOffset, InitSections[I].FileOffsetToData,
+                       "FileOffsetToData for the " +
+                           InitSections[I].SectionName + " section");
+          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 (" + Twine(MaxRawDataSize) +
----------------
jh7370 wrote:

Is this tested?

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