3 files changed, 41 insertions, 7 deletions
diff --git a/llvm/lib/CodeGen/GlobalMerge.cpp b/llvm/lib/CodeGen/GlobalMerge.cpp
index 30e12cc2ec4..8c760b724d1 100644
--- a/llvm/lib/CodeGen/GlobalMerge.cpp
+++ b/llvm/lib/CodeGen/GlobalMerge.cpp
@@ -91,6 +91,11 @@ EnableGlobalMerge("enable-global-merge", cl::Hidden,
                   cl::desc("Enable the global merge pass"),
                   cl::init(true));
 
+static cl::opt<unsigned>
+GlobalMergeMaxOffset("global-merge-max-offset", cl::Hidden,
+                     cl::desc("Set maximum offset for global merge pass"),
+                     cl::init(0));
+
 static cl::opt<bool> GlobalMergeGroupByUse(
     "global-merge-group-by-use", cl::Hidden,
     cl::desc("Improve global merge pass to look at uses"), cl::init(true));
@@ -130,6 +135,8 @@ namespace {
     /// Whether we should merge global variables that have external linkage.
     bool MergeExternalGlobals;
 
+    bool IsMachO;
+
     bool doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
                  Module &M, bool isConst, unsigned AddrSpace) const;
     /// \brief Merge everything in \p Globals for which the corresponding bit
@@ -157,10 +164,14 @@ namespace {
 
   public:
     static char ID;             // Pass identification, replacement for typeid.
-    explicit GlobalMerge(const TargetMachine *TM = nullptr,
-                         unsigned MaximalOffset = 0,
-                         bool OnlyOptimizeForSize = false,
-                         bool MergeExternalGlobals = false)
+    explicit GlobalMerge()
+        : FunctionPass(ID), TM(nullptr), MaxOffset(GlobalMergeMaxOffset),
+          OnlyOptimizeForSize(false), MergeExternalGlobals(false) {
+      initializeGlobalMergePass(*PassRegistry::getPassRegistry());
+    }
+
+    explicit GlobalMerge(const TargetMachine *TM, unsigned MaximalOffset,
+                         bool OnlyOptimizeForSize, bool MergeExternalGlobals)
         : FunctionPass(ID), TM(TM), MaxOffset(MaximalOffset),
           OnlyOptimizeForSize(OnlyOptimizeForSize),
           MergeExternalGlobals(MergeExternalGlobals) {
@@ -458,8 +469,7 @@ bool GlobalMerge::doMerge(const SmallVectorImpl<GlobalVariable *> &Globals,
       // we can also emit an alias for internal linkage as it's safe to do so.
       // It's not safe on Mach-O as the alias (and thus the portion of the
       // MergedGlobals variable) may be dead stripped at link time.
-      if (Linkage != GlobalValue::InternalLinkage ||
-          !TM->getTargetTriple().isOSBinFormatMachO()) {
+      if (Linkage != GlobalValue::InternalLinkage || !IsMachO) {
         GlobalAlias::create(Tys[idx], AddrSpace, Linkage, Name, GEP, &M);
       }
 
@@ -512,6 +522,8 @@ bool GlobalMerge::doInitialization(Module &M) {
   if (!EnableGlobalMerge)
     return false;
 
+  IsMachO = Triple(M.getTargetTriple()).isOSBinFormatMachO();
+
   auto &DL = M.getDataLayout();
   DenseMap<unsigned, SmallVector<GlobalVariable*, 16> > Globals, ConstGlobals,
                                                         BSSGlobals;
@@ -549,7 +561,8 @@ bool GlobalMerge::doInitialization(Module &M) {
       continue;
 
     if (DL.getTypeAllocSize(Ty) < MaxOffset) {
-      if (TargetLoweringObjectFile::getKindForGlobal(&GV, *TM).isBSSLocal())
+      if (TM &&
+          TargetLoweringObjectFile::getKindForGlobal(&GV, *TM).isBSSLocal())
         BSSGlobals[AddressSpace].push_back(&GV);
       else if (GV.isConstant())
         ConstGlobals[AddressSpace].push_back(&GV);
diff --git a/llvm/test/Transforms/GlobalMerge/basic.ll b/llvm/test/Transforms/GlobalMerge/basic.ll
new file mode 100644
index 00000000000..598d917f74a
--- /dev/null
+++ b/llvm/test/Transforms/GlobalMerge/basic.ll
@@ -0,0 +1,20 @@
+; RUN: opt -global-merge -global-merge-max-offset=100 -S -o - %s | FileCheck %s
+
+target datalayout = "e-p:64:64"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK: @_MergedGlobals = private global { i32, i32 } { i32 1, i32 2 }
+
+; CHECK: @a = internal alias i32, getelementptr inbounds ({ i32, i32 }, { i32, i32 }* @_MergedGlobals, i32 0, i32 0)
+@a = internal global i32 1
+
+; CHECK: @b = internal alias i32, getelementptr inbounds ({ i32, i32 }, { i32, i32 }* @_MergedGlobals, i32 0, i32 1)
+@b = internal global i32 2
+
+define void @use() {
+  ; CHECK: load i32, i32* getelementptr inbounds ({ i32, i32 }, { i32, i32 }* @_MergedGlobals, i32 0, i32 0)
+  %x = load i32, i32* @a
+  ; CHECK: load i32, i32* getelementptr inbounds ({ i32, i32 }, { i32, i32 }* @_MergedGlobals, i32 0, i32 1)
+  %y = load i32, i32* @b
+  ret void
+}
diff --git a/llvm/tools/opt/opt.cpp b/llvm/tools/opt/opt.cpp
index afa66819f11..a790ccfe356 100644
--- a/llvm/tools/opt/opt.cpp
+++ b/llvm/tools/opt/opt.cpp
@@ -362,6 +362,7 @@ int main(int argc, char **argv) {
   initializeSafeStackPass(Registry);
   initializeSjLjEHPreparePass(Registry);
   initializePreISelIntrinsicLoweringPass(Registry);
+  initializeGlobalMergePass(Registry);
 
 #ifdef LINK_POLLY_INTO_TOOLS
   polly::initializePollyPasses(Registry);