[lld-macho] Ensure all sections in __TEXT get thunks if necessary

lld/MachO/ConcatOutputSection.cpp

@@ -127,10 +127,20 @@ bool TextOutputSection::needsThunks() const {
   uint64_t isecAddr = addr;
   for (ConcatInputSection *isec : inputs)
     isecAddr = alignToPowerOf2(isecAddr, isec->align) + isec->getSize();
-  if (isecAddr - addr + in.stubs->getSize() <=
-      std::min(target->backwardBranchRange, target->forwardBranchRange))
+  // Other sections besides __text might be small enough to pass this
+  // test but nevertheless need thunks for calling into oher sections.
+  // An imperfect heuristic to use in this case is that if a section
+  // we've already processed in this segment needs thunks, so do the
+  // rest.
+  bool needsThunks = parent && parent->needsThunks;
+  if (!needsThunks &&
+      isecAddr - addr + in.stubs->getSize() <=
+          std::min(target->backwardBranchRange, target->forwardBranchRange))
     return false;
   // Yes, this program is large enough to need thunks.
+  if (parent) {
+    parent->needsThunks = true;
+  }
   for (ConcatInputSection *isec : inputs) {
     for (Reloc &r : isec->relocs) {
       if (!target->hasAttr(r.type, RelocAttrBits::BRANCH))

lld/MachO/OutputSegment.h

@@ -57,6 +57,7 @@ class OutputSegment {
   uint32_t initProt = 0;
   uint32_t flags = 0;
   uint8_t index;
+  bool needsThunks = false;
 
   llvm::TinyPtrVector<Defined *> segmentStartSymbols;
   llvm::TinyPtrVector<Defined *> segmentEndSymbols;

lld/test/MachO/arm64-thunks.s

@@ -7,6 +7,7 @@
 ## (3) a second thunk is created when the first one goes out of range
 ## (4) early calls to a dylib stub use a thunk, and later calls the stub
 ##     directly
+## (5) Thunks are created for all sections in the text segment with branches.
 ## Notes:
 ## 0x4000000 = 64 Mi = half the magnitude of the forward-branch range
 
@@ -168,6 +169,10 @@
 
 # CHECK: [[#%x, NAN_PAGE + NAN_OFFSET]] <__stubs>:
 
+# CHECK: Disassembly of section __TEXT,__lcxx_override:
+# CHECK: <_z>:
+# CHECK:  bl 0x[[#%x, A_THUNK_0]] <_a.thunk.0>
+
 .subsections_via_symbols
 .text
 
@@ -300,3 +305,12 @@ _main:
   bl _h
   bl ___nan
   ret
+
+.section __TEXT,__lcxx_override,regular,pure_instructions
+
+.globl _z
+.no_dead_strip _z
+.p2align 2
+_z:
+  bl _a
+  ret