[lld] 0f3d646 - [ELF] Simplify findOrphanPos. NFC

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2024-05-31T22:35:31-07:00
New Revision: 0f3d646cefbe00b4a1037dc68e9d76e5470e805f

URL: https://github.com/llvm/llvm-project/commit/0f3d646cefbe00b4a1037dc68e9d76e5470e805f
DIFF: https://github.com/llvm/llvm-project/commit/0f3d646cefbe00b4a1037dc68e9d76e5470e805f.diff

LOG: [ELF] Simplify findOrphanPos. NFC

Simplify the loop that considers sections of the same proximity. The two
involved conditions are due to:

* https://reviews.llvm.org/D111717 ("[ELF] Avoid adding an orphan section to a less suitable segment") and
* https://reviews.llvm.org/D112925 ("[ELF] Better resemble GNU ld when placing orphan sections into memory regions")

Added: 
    

Modified: 
    lld/ELF/Writer.cpp

Removed: 
    


################################################################################
diff  --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 05f2e95def4b3..c90bbeec2779d 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -949,25 +949,22 @@ findOrphanPos(SmallVectorImpl<SectionCommand *>::iterator b,
   }
   if (!isa<OutputDesc>(*i))
     return e;
-  auto foundSec = &cast<OutputDesc>(*i)->osec;
-
-  // Consider all existing sections with the same proximity.
-  unsigned sortRank = sec->sortRank;
-  if (script->hasPhdrsCommands() || !script->memoryRegions.empty())
-    // Prevent the orphan section to be placed before the found section. If
-    // custom program headers are defined, that helps to avoid adding it to a
-    // previous segment and changing flags of that segment, for example, making
-    // a read-only segment writable. If memory regions are defined, an orphan
-    // section should continue the same region as the found section to better
-    // resemble the behavior of GNU ld.
-    sortRank = std::max(sortRank, foundSec->sortRank);
-  for (; i != e; ++i) {
-    auto *curSecDesc = dyn_cast<OutputDesc>(*i);
-    if (!curSecDesc || !curSecDesc->osec.hasInputSections)
-      continue;
-    if (getRankProximity(sec, curSecDesc) != proximity ||
-        sortRank < curSecDesc->osec.sortRank)
-      break;
+
+  // If i's rank is larger, the orphan section can be placed before i.
+  //
+  // However, don't do this if custom program headers are defined. Otherwise,
+  // adding the orphan to a previous segment can change its flags, for example,
+  // making a read-only segment writable. If memory regions are defined, an
+  // orphan section should continue the same region as the found section to
+  // better resemble the behavior of GNU ld.
+  bool mustAfter = script->hasPhdrsCommands() || !script->memoryRegions.empty();
+  if (cast<OutputDesc>(*i)->osec.sortRank <= sec->sortRank || mustAfter) {
+    while (++i != e) {
+      auto *cur = dyn_cast<OutputDesc>(*i);
+      if (cur && cur->osec.hasInputSections &&
+          getRankProximity(sec, cur) != proximity)
+        break;
+    }
   }
 
   auto isOutputSecWithInputSections = [](SectionCommand *cmd) {