Rewrite the global merge pass to be subprogram agnostic for now.

It was previously using the subtarget to get values for the global
offset without actually checking each function as it was generating
code. Go ahead and solidify the current behavior and make the
existing FIXMEs more prominent.

As a note the ARM backend previously had a thumb1 and non-thumb1
set of defaults. Only the former was tested so I've changed the
behavior to only use that for now.

llvm-svn: 230245

1 files changed, 18 insertions, 19 deletions

diff --git a/llvm/lib/CodeGen/GlobalMerge.cpp b/llvm/lib/CodeGen/GlobalMerge.cpp
index 6da9766379e..32543b7723a 100644
--- a/llvm/lib/CodeGen/GlobalMerge.cpp
+++ b/llvm/lib/CodeGen/GlobalMerge.cpp
@@ -90,10 +90,16 @@ EnableGlobalMergeOnExternal("global-merge-on-external", cl::Hidden,
      cl::desc("Enable global merge pass on external linkage"),
      cl::init(false));
 
-STATISTIC(NumMerged      , "Number of globals merged");
+STATISTIC(NumMerged, "Number of globals merged");
 namespace {
   class GlobalMerge : public FunctionPass {
     const TargetMachine *TM;
+    const DataLayout *DL;
+    // FIXME: Infer the maximum possible offset depending on the actual users
+    // (these max offsets are different for the users inside Thumb or ARM
+    // functions), see the code that passes in the offset in the ARM backend
+    // for more information.
+    unsigned MaxOffset;
 
     bool doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
                  Module &M, bool isConst, unsigned AddrSpace) const;
@@ -117,8 +123,10 @@ namespace {
 
   public:
     static char ID;             // Pass identification, replacement for typeid.
-    explicit GlobalMerge(const TargetMachine *TM = nullptr)
-      : FunctionPass(ID), TM(TM) {
+    explicit GlobalMerge(const TargetMachine *TM = nullptr,
+                         unsigned MaximalOffset = 0)
+        : FunctionPass(ID), TM(TM), DL(TM->getDataLayout()),
+          MaxOffset(MaximalOffset) {
       initializeGlobalMergePass(*PassRegistry::getPassRegistry());
     }
 
@@ -138,22 +146,16 @@ namespace {
 } // end anonymous namespace
 
 char GlobalMerge::ID = 0;
-INITIALIZE_TM_PASS(GlobalMerge, "global-merge", "Merge global variables",
-                   false, false)
+INITIALIZE_PASS_BEGIN(GlobalMerge, "global-merge", "Merge global variables",
+                      false, false)
+INITIALIZE_PASS_END(GlobalMerge, "global-merge", "Merge global variables",
+                    false, false)
 
 bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
                           Module &M, bool isConst, unsigned AddrSpace) const {
-  const TargetLowering *TLI = TM->getSubtargetImpl()->getTargetLowering();
-  const DataLayout *DL = TM->getDataLayout();
-
-  // FIXME: Infer the maximum possible offset depending on the actual users
-  // (these max offsets are different for the users inside Thumb or ARM
-  // functions)
-  unsigned MaxOffset = TLI->getMaximalGlobalOffset();
-
   // FIXME: Find better heuristics
   std::stable_sort(Globals.begin(), Globals.end(),
-                   [DL](const GlobalVariable *GV1, const GlobalVariable *GV2) {
+                   [this](const GlobalVariable *GV1, const GlobalVariable *GV2) {
     Type *Ty1 = cast<PointerType>(GV1->getType())->getElementType();
     Type *Ty2 = cast<PointerType>(GV2->getType())->getElementType();
 
@@ -282,9 +284,6 @@ bool GlobalMerge::doInitialization(Module &M) {
 
   DenseMap<unsigned, SmallVector<GlobalVariable*, 16> > Globals, ConstGlobals,
                                                         BSSGlobals;
-  const TargetLowering *TLI = TM->getSubtargetImpl()->getTargetLowering();
-  const DataLayout *DL = TM->getDataLayout();
-  unsigned MaxOffset = TLI->getMaximalGlobalOffset();
   bool Changed = false;
   setMustKeepGlobalVariables(M);
 
@@ -357,6 +356,6 @@ bool GlobalMerge::doFinalization(Module &M) {
   return false;
 }
 
-Pass *llvm::createGlobalMergePass(const TargetMachine *TM) {
-  return new GlobalMerge(TM);
+Pass *llvm::createGlobalMergePass(const TargetMachine *TM, unsigned Offset) {
+  return new GlobalMerge(TM, Offset);
 }