[lld] e5347f2 - [lld-macho] Allow deduplicate-literals to be overridden

[Vincent Lee via llvm-commits]

Author: Vincent Lee
Date: 2022-01-18T15:42:59-08:00
New Revision: e5347f2556cbdd13235ebf5b4994ac6f5276a0dd

URL: https://github.com/llvm/llvm-project/commit/e5347f2556cbdd13235ebf5b4994ac6f5276a0dd
DIFF: https://github.com/llvm/llvm-project/commit/e5347f2556cbdd13235ebf5b4994ac6f5276a0dd.diff

LOG: [lld-macho] Allow deduplicate-literals to be overridden

It's still uncertain but whether we want to have `deduplicate-literals` be the
default flag for LLD out of the box or not. If `deduplicate-literals` is the default
behavior, then we will need a way override it and not deduplicate. Luckily, we
have `no_deduplicate` to fill this gap. For now, I've set the default to be false
which aligns with the existing behavior. That can only always be changed after
discussions on D117250.

Reviewed By: #lld-macho, int3

Differential Revision: https://reviews.llvm.org/D117387

Added: 
    

Modified: 
    lld/MachO/Driver.cpp
    lld/MachO/ld64-vs-lld.rst
    lld/test/MachO/literal-dedup.s
    lld/test/MachO/silent-ignore.s

Removed: 
    


################################################################################
diff  --git a/lld/MachO/Driver.cpp b/lld/MachO/Driver.cpp
index f4b294888b070..5761e85f619c4 100644
--- a/lld/MachO/Driver.cpp
+++ b/lld/MachO/Driver.cpp
@@ -1281,8 +1281,9 @@ bool macho::link(ArrayRef<const char *> argsArr, bool canExitEarly,
   config->emitDataInCodeInfo =
       args.hasFlag(OPT_data_in_code_info, OPT_no_data_in_code_info, true);
   config->icfLevel = getICFLevel(args);
-  config->dedupLiterals = args.hasArg(OPT_deduplicate_literals) ||
-                          config->icfLevel != ICFLevel::none;
+  config->dedupLiterals =
+      args.hasFlag(OPT_deduplicate_literals, OPT_icf_eq, false) ||
+      config->icfLevel != ICFLevel::none;
   config->warnDylibInstallName = args.hasFlag(
       OPT_warn_dylib_install_name, OPT_no_warn_dylib_install_name, false);
   config->callGraphProfileSort = args.hasFlag(

diff  --git a/lld/MachO/ld64-vs-lld.rst b/lld/MachO/ld64-vs-lld.rst
index 14fb72a2ac8fb..d40c5a4196666 100644
--- a/lld/MachO/ld64-vs-lld.rst
+++ b/lld/MachO/ld64-vs-lld.rst
@@ -4,6 +4,13 @@ LD64 vs LLD-MACHO
 
 This doc lists all significant deliberate 
diff erences in behavior between LD64 and LLD-MachO.
 
+``-no_deduplicate`` Flag
+**********************
+- LD64:
+   * This turns off ICF (deduplication pass) in the linker.
+- LLD
+   * This turns off ICF and string merging in the linker.
+
 ObjC symbols treatment
 **********************
 There are 
diff erences in how LLD and LD64 handle ObjC symbols loaded from archives.

diff  --git a/lld/test/MachO/literal-dedup.s b/lld/test/MachO/literal-dedup.s
index df74e70ff8fde..1f3fd47737d78 100644
--- a/lld/test/MachO/literal-dedup.s
+++ b/lld/test/MachO/literal-dedup.s
@@ -6,6 +6,29 @@
 # RUN: llvm-objdump --macho --section="__TEXT,__literals" --section="__DATA,ptrs" --syms %t/test | FileCheck %s
 # RUN: llvm-readobj --section-headers %t/test | FileCheck %s --check-prefix=HEADER
 
+## Make sure literal deduplication can be overridden or that the later flag wins.
+# RUN: %lld -dylib --deduplicate-literals -no_deduplicate %t/test.o %t/qux.o -o %t/no-dedup-test
+# RUN: llvm-objdump --macho --section="__TEXT,__literals" --section="__DATA,ptrs" %t/no-dedup-test | FileCheck %s --check-prefix=NO-DEDUP
+
+# RUN: %lld -dylib -no_deduplicate --deduplicate-literals %t/test.o %t/qux.o -o %t/test
+# RUN: llvm-objdump --macho --section="__TEXT,__literals" --section="__DATA,ptrs" --syms %t/test | FileCheck %s
+# RUN: llvm-readobj --section-headers %t/test | FileCheck %s --check-prefix=HEADER
+
+# NO-DEDUP-NOT:  Contents of (__TEXT,__literals) section
+# NO-DEDUP:      Contents of (__DATA,ptrs) section
+# NO-DEDUP-NEXT: __TEXT:__literal16:0xdeadbeef 0xdeadbeef 0xdeadbeef 0xdeadbeef
+# NO-DEDUP-NEXT: __TEXT:__literal16:0xdeadbeef 0xdeadbeef 0xdeadbeef 0xdeadbeef
+# NO-DEDUP-NEXT: __TEXT:__literal16:0xfeedface 0xfeedface 0xfeedface 0xfeedface
+# NO-DEDUP-NEXT: __TEXT:__literal16:0xdeadbeef 0xdeadbeef 0xdeadbeef 0xdeadbeef
+# NO-DEDUP-NEXT: __TEXT:__literal8:0xdeadbeef 0xdeadbeef
+# NO-DEDUP-NEXT: __TEXT:__literal8:0xdeadbeef 0xdeadbeef
+# NO-DEDUP-NEXT: __TEXT:__literal8:0xfeedface 0xfeedface
+# NO-DEDUP-NEXT: __TEXT:__literal8:0xdeadbeef 0xdeadbeef
+# NO-DEDUP-NEXT: __TEXT:__literal4:0xdeadbeef
+# NO-DEDUP-NEXT: __TEXT:__literal4:0xdeadbeef
+# NO-DEDUP-NEXT: __TEXT:__literal4:0xfeedface
+# NO-DEDUP-NEXT: __TEXT:__literal4:0xdeadbeef
+
 # CHECK:      Contents of (__TEXT,__literals) section
 # CHECK-NEXT: [[#%.16x,DEADBEEF16:]] ef be ad de ef be ad de ef be ad de ef be ad de
 # CHECK-NEXT: [[#%.16x,FEEDFACE16:]] ce fa ed fe ce fa ed fe ce fa ed fe ce fa ed fe

diff  --git a/lld/test/MachO/silent-ignore.s b/lld/test/MachO/silent-ignore.s
index 5700a77c9313e..efbe30ec421a0 100644
--- a/lld/test/MachO/silent-ignore.s
+++ b/lld/test/MachO/silent-ignore.s
@@ -6,7 +6,6 @@
 ## `--version` flag.)
 # RUN: %lld --version \
 # RUN:   -dynamic \
-# RUN:   -no_deduplicate \
 # RUN:   -lto_library /lib/foo \
 # RUN:   -macosx_version_min 0 \
 # RUN:   -no_dtrace_dof \