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-rw-r--r--llvm/include/llvm/InitializePasses.h1
-rw-r--r--llvm/include/llvm/Transforms/IPO.h6
-rw-r--r--llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h1
-rw-r--r--llvm/lib/Transforms/IPO/CMakeLists.txt1
-rw-r--r--llvm/lib/Transforms/IPO/ElimAvailExtern.cpp96
-rw-r--r--llvm/lib/Transforms/IPO/PassManagerBuilder.cpp12
6 files changed, 117 insertions, 0 deletions
diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
index 4f95c886800..f6b497dc78c 100644
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/include/llvm/InitializePasses.h
@@ -130,6 +130,7 @@ void initializeSanitizerCoverageModulePass(PassRegistry&);
void initializeDataFlowSanitizerPass(PassRegistry&);
void initializeScalarizerPass(PassRegistry&);
void initializeEarlyCSELegacyPassPass(PassRegistry &);
+void initializeEliminateAvailableExternallyPass(PassRegistry&);
void initializeExpandISelPseudosPass(PassRegistry&);
void initializeFunctionAttrsPass(PassRegistry&);
void initializeGCMachineCodeAnalysisPass(PassRegistry&);
diff --git a/llvm/include/llvm/Transforms/IPO.h b/llvm/include/llvm/Transforms/IPO.h
index fbd999cbc94..2ea47301bb4 100644
--- a/llvm/include/llvm/Transforms/IPO.h
+++ b/llvm/include/llvm/Transforms/IPO.h
@@ -71,6 +71,12 @@ ModulePass *createGlobalOptimizerPass();
ModulePass *createGlobalDCEPass();
//===----------------------------------------------------------------------===//
+/// This transform is designed to eliminate available external globals
+/// (functions or global variables)
+///
+ModulePass *createEliminateAvailableExternallyPass();
+
+//===----------------------------------------------------------------------===//
/// createGVExtractionPass - If deleteFn is true, this pass deletes
/// the specified global values. Otherwise, it deletes as much of the module as
/// possible, except for the global values specified.
diff --git a/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h b/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
index 5d574ae0bf0..1334dd0da23 100644
--- a/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
+++ b/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
@@ -121,6 +121,7 @@ public:
bool VerifyInput;
bool VerifyOutput;
bool MergeFunctions;
+ bool PrepareForLTO;
private:
/// ExtensionList - This is list of all of the extensions that are registered.
diff --git a/llvm/lib/Transforms/IPO/CMakeLists.txt b/llvm/lib/Transforms/IPO/CMakeLists.txt
index 3df17b920a9..336dac45e13 100644
--- a/llvm/lib/Transforms/IPO/CMakeLists.txt
+++ b/llvm/lib/Transforms/IPO/CMakeLists.txt
@@ -3,6 +3,7 @@ add_llvm_library(LLVMipo
BarrierNoopPass.cpp
ConstantMerge.cpp
DeadArgumentElimination.cpp
+ ElimAvailExtern.cpp
ExtractGV.cpp
FunctionAttrs.cpp
GlobalDCE.cpp
diff --git a/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp b/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp
new file mode 100644
index 00000000000..e70ab871b88
--- /dev/null
+++ b/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp
@@ -0,0 +1,96 @@
+//===-- ElimAvailExtern.cpp - DCE unreachable internal functions ----------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This transform is designed to eliminate available external global
+// definitions from the program, turning them into declarations.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/IPO.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Transforms/Utils/CtorUtils.h"
+#include "llvm/Transforms/Utils/GlobalStatus.h"
+#include "llvm/Pass.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "elim-avail-extern"
+
+STATISTIC(NumAliases , "Number of global aliases removed");
+STATISTIC(NumFunctions, "Number of functions removed");
+STATISTIC(NumVariables, "Number of global variables removed");
+
+namespace {
+ struct EliminateAvailableExternally : public ModulePass {
+ static char ID; // Pass identification, replacement for typeid
+ EliminateAvailableExternally() : ModulePass(ID) {
+ initializeEliminateAvailableExternallyPass(
+ *PassRegistry::getPassRegistry());
+ }
+
+ // run - Do the EliminateAvailableExternally pass on the specified module,
+ // optionally updating the specified callgraph to reflect the changes.
+ //
+ bool runOnModule(Module &M) override;
+ };
+}
+
+char EliminateAvailableExternally::ID = 0;
+INITIALIZE_PASS(EliminateAvailableExternally, "elim-avail-extern",
+ "Eliminate Available Externally Globals", false, false)
+
+ModulePass *llvm::createEliminateAvailableExternallyPass() {
+ return new EliminateAvailableExternally();
+}
+
+bool EliminateAvailableExternally::runOnModule(Module &M) {
+ bool Changed = false;
+
+ // Drop initializers of available externally global variables.
+ for (Module::global_iterator I = M.global_begin(), E = M.global_end();
+ I != E; ++I) {
+ if (!I->hasAvailableExternallyLinkage())
+ continue;
+ if (I->hasInitializer()) {
+ Constant *Init = I->getInitializer();
+ I->setInitializer(nullptr);
+ if (isSafeToDestroyConstant(Init))
+ Init->destroyConstant();
+ }
+ I->removeDeadConstantUsers();
+ I->setLinkage(GlobalValue::ExternalLinkage);
+ NumVariables++;
+ }
+
+ // Drop the bodies of available externally functions.
+ for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
+ if (!I->hasAvailableExternallyLinkage())
+ continue;
+ if (!I->isDeclaration())
+ // This will set the linkage to external
+ I->deleteBody();
+ I->removeDeadConstantUsers();
+ NumFunctions++;
+ }
+
+ // Drop targets of available externally aliases.
+ for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); I != E;
+ ++I) {
+ if (!I->hasAvailableExternallyLinkage())
+ continue;
+ I->setAliasee(nullptr);
+ I->removeDeadConstantUsers();
+ I->setLinkage(GlobalValue::ExternalLinkage);
+ NumAliases++;
+ }
+
+ return Changed;
+}
diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index 963f1bb13aa..a067a4b4525 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -105,6 +105,7 @@ PassManagerBuilder::PassManagerBuilder() {
VerifyInput = false;
VerifyOutput = false;
MergeFunctions = false;
+ PrepareForLTO = false;
}
PassManagerBuilder::~PassManagerBuilder() {
@@ -401,6 +402,17 @@ void PassManagerBuilder::populateModulePassManager(
// GlobalOpt already deletes dead functions and globals, at -O2 try a
// late pass of GlobalDCE. It is capable of deleting dead cycles.
if (OptLevel > 1) {
+ if (!PrepareForLTO) {
+ // Remove avail extern fns and globals definitions if we aren't
+ // compiling an object file for later LTO. For LTO we want to preserve
+ // these so they are eligible for inlining at link-time. Note if they
+ // are unreferenced they will be removed by GlobalDCE below, so
+ // this only impacts referenced available externally globals.
+ // Eventually they will be suppressed during codegen, but eliminating
+ // here enables more opportunity for GlobalDCE as it may make
+ // globals referenced by available external functions dead.
+ MPM.add(createEliminateAvailableExternallyPass());
+ }
MPM.add(createGlobalDCEPass()); // Remove dead fns and globals.
MPM.add(createConstantMergePass()); // Merge dup global constants
}
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