[LTO] Add support for existing Config::Freestanding option.

lto::Config has a field to control whether the build is "freestanding"
(no builtins) or not, but it is not hooked up to the code actually
running the passes.

This patch adds support for the flag to both the code that runs
optimization with the new and old pass managers, by explicitly adding a
TargetLibraryInfo instance. If Freestanding is true, all library functions
are disabled.

Reviewed By: steven_wu

Differential Revision: https://reviews.llvm.org/D94630

Author: fhahn

llvm/lib/LTO/LTOBackend.cpp

@@ -237,6 +237,12 @@ static void runNewPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
   CGSCCAnalysisManager CGAM(Conf.DebugPassManager);
   ModuleAnalysisManager MAM(Conf.DebugPassManager);
 
+  std::unique_ptr<TargetLibraryInfoImpl> TLII(
+      new TargetLibraryInfoImpl(Triple(TM->getTargetTriple())));
+  if (Conf.Freestanding)
+    TLII->disableAllFunctions();
+  FAM.registerPass([&] { return TargetLibraryAnalysis(*TLII); });
+
   // Register the AA manager first so that our version is the one used.
   FAM.registerPass([&] { return std::move(AA); });
 
@@ -302,6 +308,12 @@ static void runNewPMCustomPasses(const Config &Conf, Module &Mod,
   CGSCCAnalysisManager CGAM;
   ModuleAnalysisManager MAM;
 
+  std::unique_ptr<TargetLibraryInfoImpl> TLII(
+      new TargetLibraryInfoImpl(Triple(TM->getTargetTriple())));
+  if (Conf.Freestanding)
+    TLII->disableAllFunctions();
+  FAM.registerPass([&] { return TargetLibraryAnalysis(*TLII); });
+
   // Register the AA manager first so that our version is the one used.
   FAM.registerPass([&] { return std::move(AA); });
 
@@ -335,6 +347,8 @@ static void runOldPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
 
   PassManagerBuilder PMB;
   PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM->getTargetTriple()));
+  if (Conf.Freestanding)
+    PMB.LibraryInfo->disableAllFunctions();
   PMB.Inliner = createFunctionInliningPass();
   PMB.ExportSummary = ExportSummary;
   PMB.ImportSummary = ImportSummary;

llvm/test/LTO/X86/tli-nobuiltin.ll

@@ -11,6 +11,31 @@
 ; RUN: llvm-nm %t.o | FileCheck %s --check-prefix=LTO-FREESTANDING
 ; LTO-FREESTANDING: fprintf
 
+; Test -lto-freestanding option for LTOBackend & legacy PM.
+
+; RUN: llvm-lto2 run -r %t.bc,_fprintf,px -r %t.bc,_hello_world,px -r %t.bc,_percent_s,px  -r %t.bc,_foo,px %t.bc -o %t1.o 2>&1
+; RUN: llvm-nm %t1.o.0 | FileCheck %s --check-prefix=LTO
+
+; RUN: llvm-lto2 run -lto-freestanding -r %t.bc,_fprintf,px -r %t.bc,_hello_world,px -r %t.bc,_percent_s,px  -r %t.bc,_foo,px %t.bc -o %t2.o 2>&1
+; RUN: llvm-nm %t2.o.0 | FileCheck %s --check-prefix=LTO-FREESTANDING
+
+; Test -lto-freestanding option for LTOBackend & new PM.
+
+; RUN: llvm-lto2 run -use-new-pm -r %t.bc,_fprintf,px -r %t.bc,_hello_world,px -r %t.bc,_percent_s,px  -r %t.bc,_foo,px %t.bc -o %t1.o 2>&1
+; RUN: llvm-nm %t1.o.0 | FileCheck %s --check-prefix=LTO
+
+; RUN: llvm-lto2 run -use-new-pm -lto-freestanding -r %t.bc,_fprintf,px -r %t.bc,_hello_world,px -r %t.bc,_percent_s,px  -r %t.bc,_foo,px %t.bc -o %t2.o 2>&1
+; RUN: llvm-nm %t2.o.0 | FileCheck %s --check-prefix=LTO-FREESTANDING
+
+; Test -lto-freestanding option for LTOBackend & new PM with custom pipeline.
+
+; RUN: llvm-lto2 run -use-new-pm -opt-pipeline='default<O3>' -r %t.bc,_fprintf,px -r %t.bc,_hello_world,px -r %t.bc,_percent_s,px  -r %t.bc,_foo,px %t.bc -o %t1.o 2>&1
+; RUN: llvm-nm %t1.o.0 | FileCheck %s --check-prefix=LTO
+
+; RUN: llvm-lto2 run -use-new-pm -opt-pipeline='default<O3>' -lto-freestanding -r %t.bc,_fprintf,px -r %t.bc,_hello_world,px -r %t.bc,_percent_s,px  -r %t.bc,_foo,px %t.bc -o %t2.o 2>&1
+; RUN: llvm-nm %t2.o.0 | FileCheck %s --check-prefix=LTO-FREESTANDING
+
+
 target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.11.0"
 

llvm/tools/llvm-lto2/llvm-lto2.cpp

@@ -158,6 +158,11 @@ static cl::list<std::string>
     PassPlugins("load-pass-plugin",
                 cl::desc("Load passes from plugin library"));
 
+static cl::opt<bool> EnableFreestanding(
+    "lto-freestanding",
+    cl::desc("Enable Freestanding (disable builtins / TLI) during LTO"),
+    cl::init(false), cl::Hidden);
+
 static void check(Error E, std::string Msg) {
   if (!E)
     return;
@@ -269,6 +274,7 @@ static int run(int argc, char **argv) {
 
   Conf.OptLevel = OptLevel - '0';
   Conf.UseNewPM = UseNewPM;
+  Conf.Freestanding = EnableFreestanding;
   for (auto &PluginFN : PassPlugins)
     Conf.PassPlugins.push_back(PluginFN);
   switch (CGOptLevel) {