From 962b77008431d120a513bf7e021e5acd1660c911 Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo@fhahn.com>
Date: Fri, 22 Jan 2021 13:13:54 +0000
Subject: [PATCH] [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
---
 lib/LTO/LTOBackend.cpp        | 14 ++++++++++++++
 test/LTO/X86/tli-nobuiltin.ll | 25 +++++++++++++++++++++++++
 tools/llvm-lto2/llvm-lto2.cpp |  6 ++++++
 3 files changed, 45 insertions(+)

diff --git a/lib/LTO/LTOBackend.cpp b/lib/LTO/LTOBackend.cpp
index 83282249ef4..1796d6ba60c 100644
--- a/lib/LTO/LTOBackend.cpp
+++ b/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;
diff --git a/test/LTO/X86/tli-nobuiltin.ll b/test/LTO/X86/tli-nobuiltin.ll
index 4f6b3ef63f4..a83e4219068 100644
--- a/test/LTO/X86/tli-nobuiltin.ll
+++ b/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"
 
diff --git a/tools/llvm-lto2/llvm-lto2.cpp b/tools/llvm-lto2/llvm-lto2.cpp
index b84bfff8158..ca4278fafb8 100644
--- a/tools/llvm-lto2/llvm-lto2.cpp
+++ b/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) {