Add --print-icf-sections flag

[gbreynoo]

Summary

Currently ICF information is output through stderr if the "--verbose" flag is used. This differs to Gold for example, which uses an explicit flag to output this to stdout. This diff adds the "--print-icf-sections" and "--no-print-icf-sections" flags and changes the output message format for clarity and consistency with "--print-gc-sections". These messages are still output to stderr if using the verbose flag. However to avoid intermingled message output to console, this will not occur when the "--print-icf-sections" flag is used.

Existing tests have been modified to expect the new message format from stderr.

[gbreynoo]

Updated tests that used existing icf output

[ruiu]

ELF/Driver.cpp

647 ↗

(On Diff #130904)

hasFlag ( -> hasFlag(

ELF/ICF.cpp

436–440 ↗

(On Diff #130904)

Can you define this function

static void print(const Twine &S) {
  if (Config->PrintIcf)
    message(S);
  else
    log(S);
}

and use it?

[gbreynoo]

Changes following Rui's comments

[gbreynoo]

Changes following Rafael's comment on the mailing list:
"gold calls this option --print-icf-sections, why not use the same name?"

[grimar]

test/ELF/print-icf.s

7 ↗

(On Diff #131092)

I think it is better to use explicit way of checking the output:

1. RUN: ld.lld %t %t1 -o %t2 --icf=all --print-icf-sections --no-print-icf-sections | FileCheck %s --check-prefix=PREFIX
2. PREFIX-NOT: selected
3. PREFIX-NOT: removing

Otherwise test can pass by mistake.

[gbreynoo]

Changes following George and Rafaels comments.

[gbreynoo]

Changes following Rafael's comment:

+ auto PrintICF = [&](const Twine &prefix, size_t I) {

prefix -> Prefix

+ const auto *F = Sections[I]->File;
+ Twine S = prefix + " section '" + Sections[I]->Name + "' from file '" +
+ (F ? Twine(F->getName()) : "<internal>") + "'";

It is in general dangerous to use a Twine Value. I would suggest
writting this as:

if (!Config->Verbose && !Config->PrintIcfSections)
return;

std::string S = ....;

[ruiu]

ELF/ICF.cpp

427 ↗

(On Diff #131987)

Everything in this file is related to ICF, so "ICF" is redundant unless it is in the global namespace. I'd name this just Print.

430 ↗

(On Diff #131987)

Please avoid auto unless the actual type is obvious.

Maybe this code is a bit better.

std::string Filename = Sections[I]->File ? Sections[I]->File->getName() : "<internal>";

431–433 ↗

(On Diff #131987)

I believe you can do this (which creates a Twine and call its str() function).

std::string S = (Prefix + " section '" + Sections[I]->Name +
                  "' from file '" + (F ? F->getName() : "<internal>") +
                  "'").str();

[gbreynoo]

Changes following Rui's comments

[gbreynoo]

Change following Rui's comments, missed in last diff

[ruiu]

LGTM

lld/trunk/ELF/Config.h

struct Configuration {
   bool NoUndefinedVersion;
   bool NoinhibitExec;
   bool Nostdlib;
   bool OFormatBinary;
   bool Omagic;
   bool OptRemarksWithHotness;
   bool Pie;
   bool PrintGcSections;
+  bool PrintIcfSections;
   bool Relocatable;
   bool SaveTemps;
   bool SingleRoRx;
   bool Shared;
   bool Static = false;
   bool SysvHash = false;
   bool Target1Rel;
   bool Trace;

lld/trunk/ELF/Driver.cpp

void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   Config->OFormatBinary = isOutputFormatBinary(Args);
   Config->Omagic = Args.hasFlag(OPT_omagic, OPT_no_omagic, false);
   Config->OptRemarksFilename = Args.getLastArgValue(OPT_opt_remarks_filename);
   Config->OptRemarksWithHotness = Args.hasArg(OPT_opt_remarks_with_hotness);
   Config->Optimize = args::getInteger(Args, OPT_O, 1);
   Config->OrphanHandling = getOrphanHandling(Args);
   Config->OutputFile = Args.getLastArgValue(OPT_o);
   Config->Pie = Args.hasFlag(OPT_pie, OPT_nopie, false);
+  Config->PrintIcfSections =
+      Args.hasFlag(OPT_print_icf_sections, OPT_no_print_icf_sections, false);
   Config->PrintGcSections =
       Args.hasFlag(OPT_print_gc_sections, OPT_no_print_gc_sections, false);
   Config->Rpath = getRpath(Args);
   Config->Relocatable = Args.hasArg(OPT_relocatable);
   Config->SaveTemps = Args.hasArg(OPT_save_temps);
   Config->SearchPaths = args::getStrings(Args, OPT_library_path);
   Config->SectionStartMap = getSectionStartMap(Args);
   Config->Shared = Args.hasArg(OPT_shared);

lld/trunk/ELF/ICF.cpp

template <class ELFT> void ICF<ELFT>::run() {
   do {
     Repeat = false;
     forEachClass(
         [&](size_t Begin, size_t End) { segregate(Begin, End, false); });
   } while (Repeat);
 
   log("ICF needed " + Twine(Cnt) + " iterations");
 
+  auto Print = [&](const Twine &Prefix, size_t I) {
+    if (!Config->Verbose && !Config->PrintIcfSections)
+      return;
+    std::string Filename =
+        Sections[I]->File ? Sections[I]->File->getName() : "<internal>";
+    std::string S = (Prefix + " section '" + Sections[I]->Name +
+                     "' from file '" + Filename + "'")
+                        .str();
+    if (Config->PrintIcfSections)
+      message(S);
+    else
+      log(S);
+  };
+
   // Merge sections by the equivalence class.
   forEachClass([&](size_t Begin, size_t End) {
     if (End - Begin == 1)
       return;
 
-    log("selected " + Sections[Begin]->Name);
+    Print("selected", Begin);
     for (size_t I = Begin + 1; I < End; ++I) {
-      log("  removed " + Sections[I]->Name);
+      Print("  removing identical", I);
       Sections[Begin]->replace(Sections[I]);
     }
   });
 
   // Mark ARM Exception Index table sections that refer to folded code
   // sections as not live. These sections have an implict dependency
   // via the link order dependency.
   if (Config->EMachine == EM_ARM)

lld/trunk/ELF/Options.td

 def nopie: F<"nopie">, HelpText<"Do not create a position independent executable">;
 
 def no_omagic: Flag<["--"], "no-omagic">, MetaVarName<"<magic>">,
   HelpText<"Do not set the text data sections to be writable">;
 
 def no_print_gc_sections: F<"no-print-gc-sections">,
   HelpText<"Do not list removed unused sections">;
 
+def no_print_icf_sections: F<"no-print-icf-sections">,
+  HelpText<"Do not list identical folded sections">;
+
 def no_rosegment: F<"no-rosegment">,
   HelpText<"Do not put read-only non-executable sections in their own segment">;
 
 def no_undefined: F<"no-undefined">,
   HelpText<"Report unresolved symbols even if the linker is creating a shared library">;
 
 def no_undefined_version: F<"no-undefined-version">,
   HelpText<"Report version scripts that refer undefined symbols">;

 def pack_dyn_relocs_eq: J<"pack-dyn-relocs=">, MetaVarName<"<format>">,
   HelpText<"Pack dynamic relocations in the given format (none or android)">;
 
 def pie: F<"pie">, HelpText<"Create a position independent executable">;
 
 def print_gc_sections: F<"print-gc-sections">,
   HelpText<"List removed unused sections">;
 
+def print_icf_sections: F<"print-icf-sections">,
+  HelpText<"List identical folded sections">;
+
 def print_map: F<"print-map">,
   HelpText<"Print a link map to the standard output">;
 
 defm reproduce: Eq<"reproduce">,
   HelpText<"Dump linker invocation and input files for debugging">;
 
 defm rpath: Eq<"rpath">, HelpText<"Add a DT_RUNPATH to the output">;
 

lld/trunk/test/ELF/Inputs/print-icf.s

+.section .text.f6, "ax"
+f6:
+  mov $60, %rax
+  mov $42, %rdi
+  syscall
+
+  .section .text.f7, "ax"
+f7:
+  mov $0, %rax

lld/trunk/test/ELF/icf-absolute.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %S/Inputs/icf-absolute.s -o %t2
 # RUN: ld.lld %t %t2 -o %t3 --icf=all --verbose 2>&1 | FileCheck %s
 
-# CHECK: selected .text.f1
-# CHECK:   removed .text.f2
+# CHECK: selected section '.text.f1' from file
+# CHECK:   removing identical section '.text.f2' from file
 
 .globl _start, f1, f2
 _start:
   ret
 
 .section .text.f1, "ax"
 f1:
   .byte a1
 
 .section .text.f2, "ax"
 f2:
   .byte a2

lld/trunk/test/ELF/icf-comdat.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: ld.lld %t -o %t2 --icf=all --verbose 2>&1 | FileCheck %s
 
-# CHECK: selected .text.f1
-# CHECK:   removed .text.f2
+# CHECK: selected section '.text.f1' from file [[T:'.*']]
+# CHECK:   removing identical section '.text.f2' from file [[T]]
 
 .globl _start, f1, f2
 _start:
   ret
 
 .section .text.f1,"ax"
 f1:
   mov $60, %rax
   mov $42, %rdi
   syscall
 
 .section .text.f2,"axG",@progbits,foo,comdat
 f2:
   mov $60, %rax
   mov $42, %rdi
   syscall

lld/trunk/test/ELF/icf-i386.s

 # REQUIRES: x86
 # This test is to make sure that we can handle implicit addends properly.
 
 # RUN: llvm-mc -filetype=obj -triple=i386-unknown-linux %s -o %t
 # RUN: ld.lld %t -o %t2 --icf=all --verbose 2>&1 | FileCheck %s
 
-# CHECK:     selected .text.f1
-# CHECK:       removed .text.f2
-# CHECK-NOT:   removed .text.f3
+# CHECK:     selected section '.text.f1' from file [[T:'.*']]
+# CHECK:       removing identical section '.text.f2' from file [[T]]
+# CHECK-NOT:   removing identical section '.text.f3' from file [[T]]
 
 .globl _start, f1, f2, f3
 _start:
   ret
 
 .section .text.f1, "ax"
 f1:
   movl $42, 4(%edi)
 
 .section .text.f2, "ax"
 f2:
   movl $42, 4(%edi)
 
 .section .text.f3, "ax"
 f3:
   movl $42, 8(%edi)

lld/trunk/test/ELF/icf-merge-sec.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %S/Inputs/icf-merge-sec.s -o %t2
 # RUN: ld.lld %t %t2 -o %t3 --icf=all --verbose 2>&1 | FileCheck %s
 
-# CHECK: selected .text.f1
-# CHECK:   removed .text.f2
+# CHECK: selected section '.text.f1' from file
+# CHECK:   removing identical section '.text.f2' from file
 
 .section .rodata.str,"aMS",@progbits,1
 .asciz "foo"
 .asciz "string 1"
 .asciz "string 2"
 
 .section .text.f1,"ax"
 .globl f1
 f1:
 .quad .rodata.str

lld/trunk/test/ELF/icf-merge.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %S/Inputs/icf-merge.s -o %t1
 # RUN: ld.lld %t %t1 -o %t1.out --icf=all --verbose 2>&1 | FileCheck %s
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %S/Inputs/icf-merge2.s -o %t2
 # RUN: ld.lld %t %t2 -o %t3.out --icf=all --verbose 2>&1 | FileCheck --check-prefix=NOMERGE %s
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %S/Inputs/icf-merge3.s -o %t3
 # RUN: ld.lld %t %t3 -o %t3.out --icf=all --verbose 2>&1 | FileCheck --check-prefix=NOMERGE %s
 
-# CHECK: selected .text.f1
-# CHECK:   removed .text.f2
+# CHECK: selected section '.text.f1' from file
+# CHECK:   removing identical section '.text.f2' from file
 
-# NOMERGE-NOT: selected .text.f
+# NOMERGE-NOT: selected section '.text.f
 
 .section .rodata.str,"aMS",@progbits,1
 foo:
 .asciz "foo"
 .asciz "string 1"
 .asciz "string 2"
 
 .section .text.f1,"ax"
 .globl f1
 f1:
 lea foo+42(%rip), %rax

lld/trunk/test/ELF/icf-non-mergeable.s

 // REQUIRES: x86
 
 // This file contains two functions. They are themselves identical,
 // but because they have relocations against different data sections,
 // they are not mergeable.
 
 // RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1
 // RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux \
 // RUN:    %p/Inputs/icf-non-mergeable.s -o %t2
 
 // RUN: ld.lld %t1 %t2 -o %t3 --icf=all --verbose 2>&1 | FileCheck %s
 
-// CHECK-NOT: selected .text.f1
-// CHECK-NOT:   removed .text.f2
+// CHECK-NOT: selected section '.text.f1'
+// CHECK-NOT:   removing identical section '.text.f2'
 
 .globl _start, f1, f2, d1, d2
 _start:
   ret
 
 .section .text.f1, "ax"
 f1:
   movl $5, d1
   ret
 
 .section .text.f2, "ax"
 f2:
   movl $5, d2
   ret

lld/trunk/test/ELF/icf-none.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: ld.lld %t -o %t2 --icf=all --icf=none --verbose 2>&1 | FileCheck %s
 
-# CHECK-NOT: selected .text.f1
+# CHECK-NOT: selected section '.text.f1'
 
 .globl _start, f1, f2
 _start:
   ret
 
 .section .text.f1, "ax"
 f1:
   mov $60, %rax
   mov $42, %rdi
   syscall
 
 .section .text.f2, "ax"
 f2:
   mov $60, %rax
   mov $42, %rdi
   syscall

lld/trunk/test/ELF/icf1.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: ld.lld %t -o %t2 --icf=all --verbose 2>&1 | FileCheck %s
 
-# CHECK: selected .text.f1
-# CHECK:   removed .text.f2
+# CHECK: selected section '.text.f1' from file [[T:'.*']]
+# CHECK:   removing identical section '.text.f2' from file [[T]]
 
 .globl _start, f1, f2
 _start:
   ret
 
 .section .text.f1, "ax"
 f1:
   mov $60, %rax
   mov $42, %rdi
   syscall
 
 .section .text.f2, "ax"
 f2:
   mov $60, %rax
   mov $42, %rdi
   syscall

lld/trunk/test/ELF/icf2.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/icf2.s -o %t2
 # RUN: ld.lld %t1 %t2 -o %t --icf=all --verbose 2>&1 | FileCheck %s
 
-# CHECK: selected .text.f1
-# CHECK:   removed .text.f2
+# CHECK: selected section '.text.f1' from file
+# CHECK:   removing identical section '.text.f2' from file
 
 .globl _start, f1, f2
 _start:
   ret
 
 .section .text.f1, "ax"
 f1:
   mov $60, %rdi
   call f2

lld/trunk/test/ELF/icf3.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/icf2.s -o %t2
 # RUN: ld.lld %t1 %t2 -o %t --icf=all --verbose 2>&1 | FileCheck %s
 
-# CHECK-NOT: Selected .text.f1
-# CHECK-NOT: Selected .text.f2
+# CHECK-NOT: selected section '.text.f1' from file
+# CHECK-NOT: selected section '.text.f2' from file
 
 .globl _start, f1, f2
 _start:
   ret
 
 # This section is not mergeable because the content is different from f2.
 .section .text.f1, "ax"
 f1:
   mov $60, %rdi
   call f2
   mov $0, %rax

lld/trunk/test/ELF/icf4.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: ld.lld %t -o %t2 --icf=all --verbose 2>&1 | FileCheck %s
 
-# CHECK-NOT: Selected .text.f1
-# CHECK-NOT: Selected .text.f2
+# CHECK-NOT: selected section '.text.f1'
+# CHECK-NOT: selected section '.text.f2'
 
 .globl _start, f1, f2
 _start:
   ret
 
 .section .text.f1, "ax"
 f1:
   mov $1, %rax
 
 .section .text.f2, "ax"
 f2:
   mov $0, %rax

lld/trunk/test/ELF/icf5.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: ld.lld %t -o %t2 --icf=all --verbose 2>&1 | FileCheck %s
 
-# CHECK-NOT: Selected .text.f1
-# CHECK-NOT: Selected .text.f2
+# CHECK-NOT: selected section '.text.f1'
+# CHECK-NOT: selected section '.text.f2'
 
 .globl _start, f1, f2
 _start:
   ret
 
 .section .text.f1, "ax"
 f1:
   mov $0, %rax
 
 .section .text.f2, "awx"
 f2:
   mov $0, %rax

lld/trunk/test/ELF/icf6.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: ld.lld %t -o %t2 --icf=all --verbose 2>&1 | FileCheck %s
 
-# CHECK-NOT: Selected .text.f1
-# CHECK-NOT: Selected .text.f2
+# CHECK-NOT: selected section '.text.f1'
+# CHECK-NOT: selected section '.text.f2'
 
 .globl _start, f1, f2
 _start:
   ret
 
 .section .init, "ax"
 f1:
   mov $60, %rax
   mov $42, %rdi
   syscall
 
 .section .fini, "ax"
 f2:
   mov $60, %rax
   mov $42, %rdi
   syscall

lld/trunk/test/ELF/icf7.s

 # REQUIRES: x86
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: ld.lld %t -o %t2 --icf=all --verbose 2>&1 | FileCheck %s
 # RUN: llvm-objdump -t %t2 | FileCheck -check-prefix=ALIGN %s
 
-# CHECK: selected .text.f1
-# CHECK:   removed .text.f2
+# CHECK: selected section '.text.f1' from file [[T:'.*']]
+# CHECK:   removing identical section '.text.f2' from file [[T]]
 
 # ALIGN: 0000000000201000 .text 00000000 _start
 # ALIGN: 0000000000201100 .text 00000000 f1
 
 .globl _start, f1, f2
 _start:
   ret
 

lld/trunk/test/ELF/icf9.s

 # REQUIRES: x86
 
 ### Make sure that we do not merge data.
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: ld.lld %t -o %t2 --icf=all --verbose 2>&1 | FileCheck %s
 # RUN: llvm-readelf -S -W %t2 | FileCheck --check-prefix=SEC %s
 
 # SEC:  .rodata      PROGBITS  0000000000200120 000120 000002 00 A 0 0 1
 
-# CHECK-NOT: selected .rodata.d1
-# CHECK-NOT: selected .rodata.d2
+# CHECK-NOT: selected section '.rodata.d1'
+# CHECK-NOT: selected section '.rodata.d2'
 
 # We do merge rodata if passed --icf-data
 # RUN: ld.lld %t -o %t2 --icf=all --verbose --ignore-data-address-equality 2>&1 | FileCheck --check-prefix=DATA %s
 # RUN: llvm-readelf -S -W %t2 | FileCheck --check-prefix=DATA-SEC %s
 
-# DATA: selected .rodata.d1
-# DATA: removed .rodata.d2
+# DATA: selected section '.rodata.d1' from file [[T:'.*']]
+# DATA:   removing identical section '.rodata.d2' from file [[T]]
 
 # DATA-SEC:  .rodata      PROGBITS  0000000000200120 000120 000001 00 A 0 0 1
 
 .globl _start, d1, d2
 _start:
   ret
 
 .section .rodata.d1, "a"
 d1:
   .byte 1
 
 .section .rodata.d2, "a"
 d2:
   .byte 1

lld/trunk/test/ELF/print-icf.s

+# REQUIRES: x86
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/print-icf.s -o %t1
+# RUN: ld.lld %t %t1 -o %t2 --icf=all --print-icf-sections | FileCheck %s
+# RUN: ld.lld %t %t1 -o %t2 --icf=all --no-print-icf-sections --print-icf-sections | FileCheck %s
+# RUN: ld.lld %t %t1 -o %t2 --icf=all --print-icf-sections --no-print-icf-sections | FileCheck -allow-empty -check-prefix=PRINT %s
+
+# CHECK: selected section '.text.f2' from file [[T:'.*']]
+# CHECK:   removing identical section '.text.f4' from file [[T]]
+# CHECK:   removing identical section '.text.f7' from file [[T1:'.*']]
+# CHECK: selected section '.text.f1' from file [[T]]
+# CHECK:   removing identical section '.text.f3' from file [[T]]
+# CHECK:   removing identical section '.text.f5' from file [[T]]
+# CHECK:   removing identical section '.text.f6' from file [[T1]]
+
+# PRINT-NOT: selected
+# PRINT-NOT: removing
+
+.globl _start, f1, f2
+_start:
+  ret
+
+.section .text.f1, "ax"
+f1:
+  mov $60, %rax
+  mov $42, %rdi
+  syscall
+
+  .section .text.f2, "ax"
+f2:
+  mov $0, %rax
+
+.section .text.f3, "ax"
+f3:
+  mov $60, %rax
+  mov $42, %rdi
+  syscall
+
+.section .text.f4, "ax"
+f4:
+  mov $0, %rax
+
+.section .text.f5, "ax"
+f5:
+  mov $60, %rax
+  mov $42, %rdi
+  syscall