From ecbc812e0ccaa6d969bb8ee672bc5146cad3d757 Mon Sep 17 00:00:00 2001
From: Jake Egan <5326451+jakeegan@users.noreply.github.com>
Date: Tue, 18 Jul 2023 22:08:46 -0400
Subject: [PATCH] [NFC][XCOFF] Use common function to calculate file offset

The file offset code is repeated in nearly identical form for every derivation of SectionEntry, so make it into a method in SectionEntry instead.

Reviewed By: scott.linder

Differential Revision: https://reviews.llvm.org/D155199
---
 llvm/lib/MC/XCOFFObjectWriter.cpp | 38 +++++++++++++++++++++++++-------------
 1 file changed, 25 insertions(+), 13 deletions(-)

diff --git a/llvm/lib/MC/XCOFFObjectWriter.cpp b/llvm/lib/MC/XCOFFObjectWriter.cpp
index a00e286..5d86ed0 100644
--- a/llvm/lib/MC/XCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/XCOFFObjectWriter.cpp
@@ -122,6 +122,15 @@ struct SectionEntry {
 
   int16_t Index;
 
+  virtual uint64_t advanceFileOffset(const uint64_t MaxRawDataSize,
+                                     const uint64_t RawPointer) {
+    FileOffsetToData = RawPointer;
+    uint64_t NewPointer = RawPointer + Size;
+    if (NewPointer > MaxRawDataSize)
+      report_fatal_error("Section raw data overflowed this object file.");
+    return NewPointer;
+  }
+
   // XCOFF has special section numbers for symbols:
   // -2 Specifies N_DEBUG, a special symbolic debugging symbol.
   // -1 Specifies N_ABS, an absolute symbol. The symbol has a value but is not
@@ -189,6 +198,19 @@ struct DwarfSectionEntry : public SectionEntry {
   // is for the size the DWARF section occupies including paddings.
   uint32_t MemorySize;
 
+  // TODO: Remove this override. Loadable sections (e.g., .text, .data) may need
+  // to be aligned. Other sections generally don't need any alignment, but if
+  // they're aligned, the RawPointer should be adjusted before writing the
+  // section. Then a dwarf-specific function wouldn't be needed.
+  uint64_t advanceFileOffset(const uint64_t MaxRawDataSize,
+                             const uint64_t RawPointer) override {
+    FileOffsetToData = RawPointer;
+    uint64_t NewPointer = RawPointer + MemorySize;
+    assert(NewPointer <= MaxRawDataSize &&
+           "Section raw data overflowed this object file.");
+    return NewPointer;
+  }
+
   DwarfSectionEntry(StringRef N, int32_t Flags,
                     std::unique_ptr<XCOFFSection> Sect)
       : SectionEntry(N, Flags | XCOFF::STYP_DWARF), DwarfSect(std::move(Sect)),
@@ -1162,28 +1184,18 @@ void XCOFFObjectWriter::finalizeSectionInfo() {
     if (Sec->Index == SectionEntry::UninitializedIndex || Sec->IsVirtual)
       continue;
 
-    Sec->FileOffsetToData = RawPointer;
-    RawPointer += Sec->Size;
-    if (RawPointer > MaxRawDataSize)
-      report_fatal_error("Section raw data overflowed this object file.");
+    RawPointer = Sec->advanceFileOffset(MaxRawDataSize, RawPointer);
   }
 
   if (!DwarfSections.empty()) {
     RawPointer += PaddingsBeforeDwarf;
     for (auto &DwarfSection : DwarfSections) {
-      DwarfSection.FileOffsetToData = RawPointer;
-      RawPointer += DwarfSection.MemorySize;
-      if (RawPointer > MaxRawDataSize)
-        report_fatal_error("Section raw data overflowed this object file.");
+      RawPointer = DwarfSection.advanceFileOffset(MaxRawDataSize, RawPointer);
     }
   }
 
   if (hasExceptionSection()) {
-    ExceptionSection.FileOffsetToData = RawPointer;
-    RawPointer += ExceptionSection.Size;
-
-    assert(RawPointer <= MaxRawDataSize &&
-           "Section raw data overflowed this object file.");
+    RawPointer = ExceptionSection.advanceFileOffset(MaxRawDataSize, RawPointer);
   }
 
   for (auto *Sec : Sections) {
-- 
2.7.4