[GlobalMerge] Take into account minsize on Global users' parents.

[oota-llvm.git] / lib / CodeGen / GlobalMerge.cpp

diff --git a/lib/CodeGen/GlobalMerge.cpp b/lib/CodeGen/GlobalMerge.cpp
index 79de17567f764624c79d33deac9fab307614bdf4..df54a9c6916216b3b5bd357a3c1cb821d9c93a21 100644 (file)
--- a/lib/CodeGen/GlobalMerge.cpp
+++ b/lib/CodeGen/GlobalMerge.cpp
@@ -124,6 +124,12 @@ namespace {
     // for more information.
     unsigned MaxOffset;
 
+    /// Whether we should try to optimize for size only.
+    /// Currently, this applies a dead simple heuristic: only consider globals
+    /// used in minsize functions for merging.
+    /// FIXME: This could learn about optsize, and be used in the cost model.
+    bool OnlyOptimizeForSize;
+
     bool doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
                  Module &M, bool isConst, unsigned AddrSpace) const;
     /// \brief Merge everything in \p Globals for which the corresponding bit
@@ -152,9 +158,10 @@ namespace {
   public:
     static char ID;             // Pass identification, replacement for typeid.
     explicit GlobalMerge(const TargetMachine *TM = nullptr,
-                         unsigned MaximalOffset = 0)
+                         unsigned MaximalOffset = 0,
+                         bool OnlyOptimizeForSize = false)
         : FunctionPass(ID), TM(TM), DL(TM->getDataLayout()),
-          MaxOffset(MaximalOffset) {
+          MaxOffset(MaximalOffset), OnlyOptimizeForSize(OnlyOptimizeForSize) {
       initializeGlobalMergePass(*PassRegistry::getPassRegistry());
     }
 
@@ -290,6 +297,12 @@ bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
           continue;
 
         Function *ParentFn = I->getParent()->getParent();
+
+        // If we're only optimizing for size, ignore non-minsize functions.
+        if (OnlyOptimizeForSize &&
+            !ParentFn->hasFnAttribute(Attribute::MinSize))
+          continue;
+
         size_t UGSIdx = GlobalUsesByFunction[ParentFn];
 
         // If this is the first global the basic block uses, map it to the set
@@ -585,6 +598,7 @@ bool GlobalMerge::doFinalization(Module &M) {
   return false;
 }
 
-Pass *llvm::createGlobalMergePass(const TargetMachine *TM, unsigned Offset) {
-  return new GlobalMerge(TM, Offset);
+Pass *llvm::createGlobalMergePass(const TargetMachine *TM, unsigned Offset,
+                                  bool OnlyOptimizeForSize) {
+  return new GlobalMerge(TM, Offset, OnlyOptimizeForSize);
 }