[lld] 9482aa9 - [lld/mac] Let OutputSegment store its start address

[Nico Weber via llvm-commits]

Author: Nico Weber
Date: 2021-07-23T11:43:25-04:00
New Revision: 9482aa98e5514f8d399bc5a16d0ff33a7f746e9d

URL: https://github.com/llvm/llvm-project/commit/9482aa98e5514f8d399bc5a16d0ff33a7f746e9d
DIFF: https://github.com/llvm/llvm-project/commit/9482aa98e5514f8d399bc5a16d0ff33a7f746e9d.diff

LOG: [lld/mac] Let OutputSegment store its start address

segment$start$/segment$end$ symbols allow creating segments without
sections, so getting the segment address off the first section
won't work there. Storing the address on the segment is arguably a
bit simpler too.

No behavior change, part of PR50760.

Differential Revision: https://reviews.llvm.org/D106665

Added: 
    

Modified: 
    lld/MachO/OutputSection.cpp
    lld/MachO/OutputSegment.h
    lld/MachO/SyntheticSections.cpp
    lld/MachO/Writer.cpp

Removed: 
    


################################################################################
diff  --git a/lld/MachO/OutputSection.cpp b/lld/MachO/OutputSection.cpp
index c006828267cf..7cf94a6a00d4 100644
--- a/lld/MachO/OutputSection.cpp
+++ b/lld/MachO/OutputSection.cpp
@@ -14,5 +14,5 @@ using namespace lld;
 using namespace lld::macho;
 
 uint64_t OutputSection::getSegmentOffset() const {
-  return addr - parent->firstSection()->addr;
+  return addr - parent->addr;
 }

diff  --git a/lld/MachO/OutputSegment.h b/lld/MachO/OutputSegment.h
index cd1fabbc7cf3..10d60b989a9b 100644
--- a/lld/MachO/OutputSegment.h
+++ b/lld/MachO/OutputSegment.h
@@ -39,9 +39,6 @@ class InputSection;
 
 class OutputSegment {
 public:
-  const OutputSection *firstSection() const { return sections.front(); }
-  const OutputSection *lastSection() const { return sections.back(); }
-
   void addOutputSection(OutputSection *os);
   void sortOutputSections();
 
@@ -50,6 +47,7 @@ class OutputSegment {
 
   uint64_t fileOff = 0;
   uint64_t fileSize = 0;
+  uint64_t addr = 0;
   uint64_t vmSize = 0;
   int inputOrder = UnspecifiedInputOrder;
   StringRef name;

diff  --git a/lld/MachO/SyntheticSections.cpp b/lld/MachO/SyntheticSections.cpp
index 70123167f282..f49340677270 100644
--- a/lld/MachO/SyntheticSections.cpp
+++ b/lld/MachO/SyntheticSections.cpp
@@ -693,7 +693,7 @@ uint32_t LazyBindingSection::encode(const DylibSymbol &sym) {
   OutputSegment *dataSeg = in.lazyPointers->parent;
   os << static_cast<uint8_t>(BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB |
                              dataSeg->index);
-  uint64_t offset = in.lazyPointers->addr - dataSeg->firstSection()->addr +
+  uint64_t offset = in.lazyPointers->addr - dataSeg->addr +
                     sym.stubsIndex * target->wordSize;
   encodeULEB128(offset, os);
   encodeDylibOrdinal(ordinalForDylibSymbol(sym), os);

diff  --git a/lld/MachO/Writer.cpp b/lld/MachO/Writer.cpp
index 81b3491cdb9b..416fef7984ec 100644
--- a/lld/MachO/Writer.cpp
+++ b/lld/MachO/Writer.cpp
@@ -239,10 +239,7 @@ template <class LP> class LCSegment final : public LoadCommand {
     c->maxprot = seg->maxProt;
     c->initprot = seg->initProt;
 
-    if (seg->getSections().empty())
-      return;
-
-    c->vmaddr = seg->firstSection()->addr;
+    c->vmaddr = seg->addr;
     c->vmsize = seg->vmSize;
     c->filesize = seg->fileSize;
     c->nsects = seg->numNonHiddenSections();
@@ -980,6 +977,7 @@ void Writer::finalizeAddresses() {
   for (OutputSegment *seg : outputSegments) {
     if (seg == linkEditSegment)
       continue;
+    seg->addr = addr;
     assignAddresses(seg);
     // codesign / libstuff checks for segment ordering by verifying that
     // `fileOff + fileSize == next segment fileOff`. So we call alignTo() before
@@ -987,7 +985,7 @@ void Writer::finalizeAddresses() {
     // contiguous. We handle addr / vmSize similarly for the same reason.
     fileOff = alignTo(fileOff, pageSize);
     addr = alignTo(addr, pageSize);
-    seg->vmSize = addr - seg->firstSection()->addr;
+    seg->vmSize = addr - seg->addr;
     seg->fileSize = fileOff - seg->fileOff;
   }
 }
@@ -1013,9 +1011,10 @@ void Writer::finalizeLinkEditSegment() {
 
   // Now that __LINKEDIT is filled out, do a proper calculation of its
   // addresses and offsets.
+  linkEditSegment->addr = addr;
   assignAddresses(linkEditSegment);
   // No need to page-align fileOff / addr here since this is the last segment.
-  linkEditSegment->vmSize = addr - linkEditSegment->firstSection()->addr;
+  linkEditSegment->vmSize = addr - linkEditSegment->addr;
   linkEditSegment->fileSize = fileOff - linkEditSegment->fileOff;
 }