[lld] 141391a - [lld] Fix -ObjC load behavior with LTO (#92162)

[via llvm-commits]

Author: Nuri Amari
Date: 2024-05-15T09:21:02-07:00
New Revision: 141391ad2f22885342935442642c6c892f43e1ed

URL: https://github.com/llvm/llvm-project/commit/141391ad2f22885342935442642c6c892f43e1ed
DIFF: https://github.com/llvm/llvm-project/commit/141391ad2f22885342935442642c6c892f43e1ed.diff

LOG: [lld] Fix -ObjC load behavior with LTO (#92162)

When -ObjC is passed, the linker must force load any object files that
contain special sections that store Objective-C / Swift information that
is used at runtime.

This should work regadless if input files are bitcode or native, but it
was not working with bitcode. This is because the sections that identify
an object file that should be loaded were inconsistent when dealing with
a native file vs bitcode file. In particular, bitcode files were not
searched for `__TEXT,__swift` prefixed sections, while native files
were.

This means LLD wasn't loading certain bitcode files and forcing the user
to introduce --force-load to their linker invocation for that archive.

Co-authored-by: Nuri Amari <nuriamari at fb.com>

Added: 
    

Modified: 
    lld/test/MachO/objc.s
    llvm/lib/Bitcode/Reader/BitcodeReader.cpp

Removed: 
    


################################################################################
diff  --git a/lld/test/MachO/objc.s b/lld/test/MachO/objc.s
index e7074141f0113..dbb9f1df27571 100644
--- a/lld/test/MachO/objc.s
+++ b/lld/test/MachO/objc.s
@@ -5,12 +5,14 @@
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/has-objc-category.s -o %t/has-objc-category.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/has-objc-symbol-and-category.s -o %t/has-objc-symbol-and-category.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/has-swift.s -o %t/has-swift.o
+# RUN: llvm-as %t/has-swift-ir-loaded.ll -o %t/has-swift-ir-loaded.o
+# RUN: llvm-as %t/has-swift-ir-not-loaded.ll -o %t/has-swift-ir-not-loaded.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/has-swift-proto.s -o %t/has-swift-proto.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/no-objc.s -o %t/no-objc.o
 ## Make sure we don't mis-parse a 32-bit file as 64-bit
 # RUN: llvm-mc -filetype=obj -triple=armv7-apple-watchos %t/no-objc.s -o %t/wrong-arch.o
-# RUN: llvm-ar rcs %t/libHasSomeObjC.a %t/no-objc.o %t/has-objc-symbol.o %t/has-objc-category.o %t/has-swift.o %t/has-swift-proto.o %t/wrong-arch.o
-# RUN: llvm-ar rcs %t/libHasSomeObjC2.a %t/no-objc.o %t/has-objc-symbol-and-category.o %t/has-swift.o %t/has-swift-proto.o %t/wrong-arch.o
+# RUN: llvm-ar rcs %t/libHasSomeObjC.a %t/no-objc.o %t/has-objc-symbol.o %t/has-objc-category.o %t/has-swift.o %t/has-swift-proto.o %t/has-swift-ir-loaded.o %t/has-swift-ir-not-loaded.o %t/wrong-arch.o
+# RUN: llvm-ar rcs %t/libHasSomeObjC2.a %t/no-objc.o %t/has-objc-symbol-and-category.o %t/has-swift.o %t/has-swift-proto.o %t/has-swift-ir-loaded.o %t/has-swift-ir-not-loaded.o %t/wrong-arch.o
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/test.s -o %t/test.o
 
@@ -20,7 +22,7 @@
 # RUN: %lld -lSystem %t/test.o -o %t/test -L%t -lHasSomeObjC2 -ObjC
 # RUN: llvm-objdump --section-headers --syms %t/test | FileCheck %s --check-prefix=OBJC
 
-# RUN: %no-fatal-warnings-lld -lSystem %t/test.o -o %t/test --start-lib %t/no-objc.o %t/has-objc-symbol.o %t/has-objc-category.o %t/has-swift.o %t/has-swift-proto.o %t/wrong-arch.o --end-lib -ObjC 2>&1 \
+# RUN: %no-fatal-warnings-lld -lSystem %t/test.o -o %t/test --start-lib %t/no-objc.o %t/has-objc-symbol.o %t/has-objc-category.o %t/has-swift.o %t/has-swift-proto.o %t/has-swift-ir-loaded.o %t/has-swift-ir-not-loaded.o %t/wrong-arch.o --end-lib -ObjC 2>&1 \
 # RUN:     | FileCheck -check-prefix=WARNING %s
 # RUN: llvm-objdump --section-headers --syms %t/test | FileCheck %s --check-prefix=OBJC
 
@@ -36,6 +38,7 @@
 # OBJC-NEXT:    4 has_objc_symbol {{.*}}      DATA
 # OBJC-EMPTY:
 # OBJC-NEXT:  SYMBOL TABLE:
+# OBJC-DAG:   g     O __TEXT,__swift _foo
 # OBJC-DAG:   g     F __TEXT,__text _main
 # OBJC-DAG:   g     F __TEXT,__text _OBJC_CLASS_$_MyObject
 # OBJC-DAG:   g     O __TEXT,__swift5_fieldmd $s7somelib4Blah_pMF
@@ -100,6 +103,20 @@ _has_dup:
 .section __TEXT,__swift
 .quad 0x1234
 
+#--- has-swift-ir-loaded.ll
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+target triple = "x86_64-apple-darwin"
+
+ at foo = global i64 1234, section "__TEXT,__swift"
+ at llvm.used = appending global [1 x ptr] [ptr @foo]
+
+#--- has-swift-ir-not-loaded.ll
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+target triple = "x86_64-apple-darwin"
+
+ at bar = global i64 1234
+ at llvm.used = appending global [1 x ptr] [ptr @bar]
+
 #--- has-swift-proto.s
 .section __TEXT,__swift5_fieldmd
 .globl $s7somelib4Blah_pMF

diff  --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 19a15209f8b66..e64051cf53862 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -306,7 +306,8 @@ static Expected<bool> hasObjCCategoryInModule(BitstreamCursor &Stream) {
         return error("Invalid section name record");
       // Check for the i386 and other (x86_64, ARM) conventions
       if (S.find("__DATA,__objc_catlist") != std::string::npos ||
-          S.find("__OBJC,__category") != std::string::npos)
+          S.find("__OBJC,__category") != std::string::npos ||
+          S.find("__TEXT,__swift") != std::string::npos)
         return true;
       break;
     }