[lld-macho] Fold cfstrings with --deduplicate-literals

Similar to cstrings ld64 always deduplicates cfstrings. This was already being done when enabling ICF, but for debug builds you may want to flip this on if you cannot eliminate your instances of this, so this change makes --deduplicate-literals also apply to cfstrings. Differential Revision: https://reviews.llvm.org/D130134
llvm · Jul 20, 2022 · 15f685e · 15f685e
1 parent a73a84c
commit 15f685e
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Showing 5 changed files with 26 additions and 17 deletions.
diff --git a/lld/MachO/Driver.cpp b/lld/MachO/Driver.cpp
@@ -1666,7 +1666,9 @@ bool macho::link(ArrayRef<const char *> argsArr, llvm::raw_ostream &stdoutOS,
     if (config->icfLevel != ICFLevel::none) {
       if (config->icfLevel == ICFLevel::safe)
         markAddrSigSymbols();
-      foldIdenticalSections();
+      foldIdenticalSections(/*onlyCfStrings=*/false);
+    } else if (config->dedupLiterals) {
+      foldIdenticalSections(/*onlyCfStrings=*/true);
     }
 
     // Write to an output file.

diff --git a/lld/MachO/ICF.cpp b/lld/MachO/ICF.cpp
@@ -395,7 +395,7 @@ void macho::markAddrSigSymbols() {
   }
 }
 
-void macho::foldIdenticalSections() {
+void macho::foldIdenticalSections(bool onlyCfStrings) {
   TimeTraceScope timeScope("Fold Identical Code Sections");
   // The ICF equivalence-class segregation algorithm relies on pre-computed
   // hashes of InputSection::data for the ConcatOutputSection::inputs and all
@@ -416,6 +416,7 @@ void macho::foldIdenticalSections() {
   for (ConcatInputSection *isec : inputSections) {
     // FIXME: consider non-code __text sections as hashable?
     bool isHashable =
+        (!onlyCfStrings || isCfStringSection(isec)) &&
         (isCodeSection(isec) || isCfStringSection(isec) ||
          isClassRefsSection(isec) || isGccExceptTabSection(isec)) &&
         !isec->keepUnique && !isec->shouldOmitFromOutput() &&

diff --git a/lld/MachO/ICF.h b/lld/MachO/ICF.h
@@ -19,7 +19,7 @@ class Symbol;
 
 void markAddrSigSymbols();
 void markSymAsAddrSig(Symbol *s);
-void foldIdenticalSections();
+void foldIdenticalSections(bool onlyCfStrings);
 
 } // namespace macho
 } // namespace lld

diff --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp
@@ -263,11 +263,15 @@ static Optional<size_t> getRecordSize(StringRef segname, StringRef name) {
     if (segname == segment_names::ld)
       return target->wordSize == 8 ? 32 : 20;
   }
-  if (config->icfLevel == ICFLevel::none)
+  if (!config->dedupLiterals)
     return {};
 
   if (name == section_names::cfString && segname == segment_names::data)
     return target->wordSize == 8 ? 32 : 16;
+
+  if (config->icfLevel == ICFLevel::none)
+    return {};
+
   if (name == section_names::objcClassRefs && segname == segment_names::data)
     return target->wordSize;
   return {};

diff --git a/lld/test/MachO/cfstring-dedup.s b/lld/test/MachO/cfstring-dedup.s
@@ -3,7 +3,9 @@
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/foo1.s -o %t/foo1.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/foo2.s -o %t/foo2.o
 # RUN: %lld -dylib --icf=all -framework CoreFoundation %t/foo1.o %t/foo2.o -o %t/foo
-# RUN: llvm-objdump --macho --rebase --bind --syms -d %t/foo | FileCheck %s
+# RUN: llvm-objdump --macho --rebase --bind --syms -d %t/foo | FileCheck %s --check-prefixes=CHECK,LITERALS
+# RUN: %lld -dylib --deduplicate-literals -framework CoreFoundation %t/foo1.o %t/foo2.o -o %t/foo
+# RUN: llvm-objdump --macho --rebase --bind --syms -d %t/foo | FileCheck %s --check-prefix=LITERALS
 
 # CHECK:       (__TEXT,__text) section
 # CHECK-NEXT:  _foo1:
@@ -22,18 +24,18 @@
 # CHECK-DAG:   [[#FOO]]        g     F __TEXT,__text _foo2
 
 ## Make sure we don't emit redundant bind / rebase opcodes for folded sections.
-# CHECK:       Rebase table:
-# CHECK-NEXT:  segment  section          address  type
-# CHECK-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer
-# CHECK-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer
-# CHECK-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer
-# CHECK-EMPTY:
-# CHECK-NEXT:  Bind table:
-# CHECK-NEXT:  segment      section      address  type       addend dylib            symbol
-# CHECK-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer         0 CoreFoundation   ___CFConstantStringClassReference
-# CHECK-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer         0 CoreFoundation   ___CFConstantStringClassReference
-# CHECK-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer         0 CoreFoundation   ___CFConstantStringClassReference
-# CHECK-EMPTY:
+# LITERALS:       Rebase table:
+# LITERALS-NEXT:  segment  section          address  type
+# LITERALS-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer
+# LITERALS-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer
+# LITERALS-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer
+# LITERALS-EMPTY:
+# LITERALS-NEXT:  Bind table:
+# LITERALS-NEXT:  segment      section      address  type       addend dylib            symbol
+# LITERALS-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer         0 CoreFoundation   ___CFConstantStringClassReference
+# LITERALS-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer         0 CoreFoundation   ___CFConstantStringClassReference
+# LITERALS-NEXT:  __DATA_CONST __cfstring   {{.*}}   pointer         0 CoreFoundation   ___CFConstantStringClassReference
+# LITERALS-EMPTY:
 
 #--- foo1.s
 .cstring