[PATCH] D116263: [lld-macho] Fix alignment of TLV data sections

[Mike Hommey via Phabricator via llvm-commits]

glandium created this revision.
Herald added a project: lld-macho.
Herald added a reviewer: lld-macho.
glandium requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D116263

Files:
  lld/MachO/Writer.cpp
  lld/test/MachO/tlv.s


Index: lld/test/MachO/tlv.s
===================================================================
--- lld/test/MachO/tlv.s
+++ lld/test/MachO/tlv.s
@@ -41,6 +41,7 @@
 # TBSS:       <_f>:
 # TBSS-NEXT:  leaq    {{.*}}(%rip), %rax  ## {{.*}} <_baz>
 # TBSS-NEXT:  leaq    {{.*}}(%rip), %rax  ## {{.*}} <_qux>
+# TBSS-NEXT:  leaq    {{.*}}(%rip), %rax  ## {{.*}} <_hoge>
 # TBSS-NEXT:  retq
 
 # REG-TLVP:      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
@@ -53,10 +54,12 @@
 
 # REG-TBSS-TLVP:      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 # REG-TBSS-TLVP-NEXT: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-# REG-TBSS-TLVP-NEXT: 00 00 00 00 00 00 00 00 08 00 00 00 00 00 00 00
+# REG-TBSS-TLVP-NEXT: 00 00 00 00 00 00 00 00 10 00 00 00 00 00 00 00
 # REG-TBSS-TLVP-NEXT: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-# REG-TBSS-TLVP-NEXT: 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
-# REG-TBSS-TLVP-NEXT: 00 00 00 00 00 00 00 00 18 00 00 00 00 00 00 00
+# REG-TBSS-TLVP-NEXT: 20 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+# REG-TBSS-TLVP-NEXT: 00 00 00 00 00 00 00 00 28 00 00 00 00 00 00 00
+# REG-TBSS-TLVP-NEXT: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+# REG-TBSS-TLVP-NEXT: 30 00 00 00 00 00 00 00
 
 ## Make sure we don't emit rebase opcodes for relocations in __thread_vars.
 # LINKEDIT:       Rebase table:
@@ -102,10 +105,12 @@
 _f:
   mov _baz at TLVP(%rip), %rax
   mov _qux at TLVP(%rip), %rax
+  mov _hoge at TLVP(%rip), %rax
   ret
 
 .tbss _baz$tlv$init, 8, 3
 .tbss _qux$tlv$init, 8, 3
+.tbss _hoge$tlv$init, 16, 4
 
 .section __DATA,__thread_vars,thread_local_variables
 _baz:
@@ -116,3 +121,7 @@
   .quad  __tlv_bootstrap
   .quad  0
   .quad  _qux$tlv$init
+_hoge:
+  .quad  __tlv_bootstrap
+  .quad  0
+  .quad  _hoge$tlv$init
Index: lld/MachO/Writer.cpp
===================================================================
--- lld/MachO/Writer.cpp
+++ lld/MachO/Writer.cpp
@@ -908,13 +908,29 @@
   uint32_t sectionIndex = 0;
   for (OutputSegment *seg : outputSegments) {
     seg->sortOutputSections();
+    // References from thread-local variable sections are treated as offsets
+    // relative to the start of the thread-local data memory area, which
+    // is initialized via copying all the TLV data sections (which are all
+    // contiguous). If later data sections require a greater alignment than
+    // earlier ones, the offsets of data within those sections won't be
+    // guaranteed to aligned unless we normalize alignments. We use the largest
+    // alignment for all TLV data sections.
+    uint32_t tlv_align = 0;
+    for (OutputSection *osec : seg->getSections()) {
+      if (isThreadLocalData(osec->flags) && osec->align > tlv_align) {
+        tlv_align = osec->align;
+      }
+    }
     for (OutputSection *osec : seg->getSections()) {
       // Now that the output sections are sorted, assign the final
       // output section indices.
       if (!osec->isHidden())
         osec->index = ++sectionIndex;
-      if (!firstTLVDataSection && isThreadLocalData(osec->flags))
-        firstTLVDataSection = osec;
+      if (isThreadLocalData(osec->flags)) {
+        if (!firstTLVDataSection)
+          firstTLVDataSection = osec;
+	osec->align = tlv_align;
+      }
 
       if (!isecPriorities.empty()) {
         if (auto *merged = dyn_cast<ConcatOutputSection>(osec)) {


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