[lld] r266953 - [LTO] Discard names for Values that are not global.

[Davide Italiano via llvm-commits]

r267020, thanks for benchmarking!

On Thu, Apr 21, 2016 at 6:59 AM, Rafael Espíndola
<rafael.espindola at gmail.com> wrote:
> According to heaptrack this takes the peak memory consumption when
> linking llvm-as from 185.14 MB to 159.89MB, so I would highly
> recommend changing the default now :-)
>
> Cheers,
> Rafael
>
>
> On 21 April 2016 at 00:46, Davide Italiano via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>> Author: davide
>> Date: Wed Apr 20 23:46:22 2016
>> New Revision: 266953
>>r267020
>> URL: http://llvm.org/viewvc/llvm-project?rev=266953&view=rev
>> Log:
>> [LTO] Discard names for Values that are not global.
>>
>> This is not on by default (but it might be in the future).
>> The knob to enable the optimization is -lto-discard-value-names.
>>
>> Added:
>>     lld/trunk/test/ELF/lto/discard-value-names.ll
>> Modified:
>>     lld/trunk/ELF/Config.h
>>     lld/trunk/ELF/Driver.cpp
>>     lld/trunk/ELF/LTO.h
>>     lld/trunk/ELF/Options.td
>>
>> Modified: lld/trunk/ELF/Config.h
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Config.h?rev=266953&r1=266952&r2=266953&view=diff
>> ==============================================================================
>> --- lld/trunk/ELF/Config.h (original)
>> +++ lld/trunk/ELF/Config.h Wed Apr 20 23:46:22 2016
>> @@ -58,6 +58,7 @@ struct Configuration {
>>    bool Demangle = true;
>>    bool DisableVerify;
>>    bool DiscardAll;
>> +  bool DiscardValueNames;
>>    bool DiscardLocals;
>>    bool DiscardNone;
>>    bool EhFrameHdr;
>>
>> Modified: lld/trunk/ELF/Driver.cpp
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Driver.cpp?rev=266953&r1=266952&r2=266953&view=diff
>> ==============================================================================
>> --- lld/trunk/ELF/Driver.cpp (original)
>> +++ lld/trunk/ELF/Driver.cpp Wed Apr 20 23:46:22 2016
>> @@ -289,6 +289,7 @@ void LinkerDriver::readConfigs(opt::Inpu
>>    Config->Demangle = !Args.hasArg(OPT_no_demangle);
>>    Config->DisableVerify = Args.hasArg(OPT_disable_verify);
>>    Config->DiscardAll = Args.hasArg(OPT_discard_all);
>> +  Config->DiscardValueNames = Args.hasArg(OPT_lto_discard_value_names);
>>    Config->DiscardLocals = Args.hasArg(OPT_discard_locals);
>>    Config->DiscardNone = Args.hasArg(OPT_discard_none);
>>    Config->EhFrameHdr = Args.hasArg(OPT_eh_frame_hdr);
>>
>> Modified: lld/trunk/ELF/LTO.h
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LTO.h?rev=266953&r1=266952&r2=266953&view=diff
>> ==============================================================================
>> --- lld/trunk/ELF/LTO.h (original)
>> +++ lld/trunk/ELF/LTO.h Wed Apr 20 23:46:22 2016
>> @@ -21,6 +21,7 @@
>>  #ifndef LLD_ELF_LTO_H
>>  #define LLD_ELF_LTO_H
>>
>> +#include "Config.h"
>>  #include "lld/Core/LLVM.h"
>>  #include "llvm/ADT/SmallString.h"
>>  #include "llvm/ADT/StringSet.h"
>> @@ -41,6 +42,7 @@ public:
>>
>>    BitcodeCompiler()
>>        : Combined(new llvm::Module("ld-temp.o", Context)), Mover(*Combined) {
>> +    Context.setDiscardValueNames(Config->DiscardValueNames);
>>      Context.enableDebugTypeODRUniquing();
>>    }
>>
>>
>> Modified: lld/trunk/ELF/Options.td
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Options.td?rev=266953&r1=266952&r2=266953&view=diff
>> ==============================================================================
>> --- lld/trunk/ELF/Options.td (original)
>> +++ lld/trunk/ELF/Options.td Wed Apr 20 23:46:22 2016
>> @@ -238,6 +238,7 @@ def G : Separate<["-"], "G">;
>>  def alias_version_script_version_script : Joined<["--"], "version-script=">, Alias<version_script>;
>>
>>  // LTO-related options.
>> +def lto_discard_value_names : Flag<["-"], "lto-discard-value-names">;
>>  def lto_jobs : Joined<["--"], "lto-jobs=">,
>>    HelpText<"Number of threads to run codegen">;
>>  def disable_verify : Flag<["-"], "disable-verify">;
>>
>> Added: lld/trunk/test/ELF/lto/discard-value-names.ll
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/lto/discard-value-names.ll?rev=266953&view=auto
>> ==============================================================================
>> --- lld/trunk/test/ELF/lto/discard-value-names.ll (added)
>> +++ lld/trunk/test/ELF/lto/discard-value-names.ll Wed Apr 20 23:46:22 2016
>> @@ -0,0 +1,33 @@
>> +; RUN: llvm-as %s -o %t.o
>> +
>> +; RUN: ld.lld -m elf_x86_64 -shared -save-temps %t.o -o %t2.o
>> +; RUN: llvm-dis < %t2.o.lto.bc | FileCheck %s
>> +
>> +; RUN: ld.lld -m elf_x86_64 -lto-discard-value-names -shared -save-temps %t.o -o %t2.o
>> +; RUN: llvm-dis < %t2.o.lto.bc | FileCheck --check-prefix=NONAME %s
>> +
>> +; CHECK: @GlobalValueName
>> +; CHECK: @foo(i32 %in)
>> +; CHECK: somelabel:
>> +; CHECK:  %GV = load i32, i32* @GlobalValueName
>> +; CHECK:  %add = add i32 %in, %GV
>> +; CHECK:  ret i32 %add
>> +
>> +; NONAME: @GlobalValueName
>> +; NONAME: @foo(i32)
>> +; NONAME-NOT: somelabel:
>> +; NONAME:  %2 = load i32, i32* @GlobalValueName
>> +; NONAME:  %3 = add i32 %0, %2
>> +; NONAME:  ret i32 %3
>> +
>> +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
>> +target triple = "x86_64-unknown-linux-gnu"
>> +
>> + at GlobalValueName = global i32 0
>> +
>> +define i32 @foo(i32 %in) {
>> +somelabel:
>> +  %GV = load i32, i32* @GlobalValueName
>> +  %add = add i32 %in, %GV
>> +  ret i32 %add
>> +}
>>
>>
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-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare