[llvm] r230245 - Rewrite the global merge pass to be subprogram agnostic for now.

Eric Christopher echristo at gmail.com
Mon Feb 23 11:28:46 PST 2015


Author: echristo
Date: Mon Feb 23 13:28:45 2015
New Revision: 230245

URL: http://llvm.org/viewvc/llvm-project?rev=230245&view=rev
Log:
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.

Modified:
    llvm/trunk/include/llvm/Target/TargetLowering.h
    llvm/trunk/include/llvm/Transforms/Scalar.h
    llvm/trunk/lib/CodeGen/GlobalMerge.cpp
    llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
    llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.h
    llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp
    llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
    llvm/trunk/lib/Target/ARM/ARMISelLowering.h
    llvm/trunk/lib/Target/ARM/ARMTargetMachine.cpp

Modified: llvm/trunk/include/llvm/Target/TargetLowering.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Target/TargetLowering.h?rev=230245&r1=230244&r2=230245&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Target/TargetLowering.h (original)
+++ llvm/trunk/include/llvm/Target/TargetLowering.h Mon Feb 23 13:28:45 2015
@@ -959,12 +959,6 @@ public:
     return false;
   }
 
-  /// Returns the maximal possible offset which can be used for loads / stores
-  /// from the global.
-  virtual unsigned getMaximalGlobalOffset() const {
-    return 0;
-  }
-
   /// Returns true if a cast between SrcAS and DestAS is a noop.
   virtual bool isNoopAddrSpaceCast(unsigned SrcAS, unsigned DestAS) const {
     return false;

Modified: llvm/trunk/include/llvm/Transforms/Scalar.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Scalar.h?rev=230245&r1=230244&r2=230245&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Scalar.h (original)
+++ llvm/trunk/include/llvm/Transforms/Scalar.h Mon Feb 23 13:28:45 2015
@@ -145,7 +145,7 @@ Pass *createLICMPass();
 //
 Pass *createLoopStrengthReducePass();
 
-Pass *createGlobalMergePass(const TargetMachine *TM = nullptr);
+Pass *createGlobalMergePass(const TargetMachine *TM, unsigned MaximalOffset);
 
 //===----------------------------------------------------------------------===//
 //

Modified: llvm/trunk/lib/CodeGen/GlobalMerge.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/GlobalMerge.cpp?rev=230245&r1=230244&r2=230245&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/GlobalMerge.cpp (original)
+++ llvm/trunk/lib/CodeGen/GlobalMerge.cpp Mon Feb 23 13:28:45 2015
@@ -90,10 +90,16 @@ EnableGlobalMergeOnExternal("global-merg
      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(Modul
 
   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
   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);
 }

Modified: llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp?rev=230245&r1=230244&r2=230245&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp Mon Feb 23 13:28:45 2015
@@ -730,13 +730,6 @@ MVT AArch64TargetLowering::getScalarShif
   return MVT::i64;
 }
 
-unsigned AArch64TargetLowering::getMaximalGlobalOffset() const {
-  // FIXME: On AArch64, this depends on the type.
-  // Basically, the addressable offsets are up to 4095 * Ty.getSizeInBytes().
-  // and the offset has to be a multiple of the related size in bytes.
-  return 4095;
-}
-
 FastISel *
 AArch64TargetLowering::createFastISel(FunctionLoweringInfo &funcInfo,
                                       const TargetLibraryInfo *libInfo) const {

Modified: llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.h?rev=230245&r1=230244&r2=230245&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.h (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.h Mon Feb 23 13:28:45 2015
@@ -246,10 +246,6 @@ public:
   /// getFunctionAlignment - Return the Log2 alignment of this function.
   unsigned getFunctionAlignment(const Function *F) const;
 
-  /// getMaximalGlobalOffset - Returns the maximal possible offset which can
-  /// be used for loads / stores from the global.
-  unsigned getMaximalGlobalOffset() const override;
-
   /// Returns true if a cast between SrcAS and DestAS is a noop.
   bool isNoopAddrSpaceCast(unsigned SrcAS, unsigned DestAS) const override {
     // Addrspacecasts are always noops.

Modified: llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp?rev=230245&r1=230244&r2=230245&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64TargetMachine.cpp Mon Feb 23 13:28:45 2015
@@ -236,8 +236,11 @@ bool AArch64PassConfig::addPreISel() {
   // get a chance to be merged
   if (TM->getOptLevel() != CodeGenOpt::None && EnablePromoteConstant)
     addPass(createAArch64PromoteConstantPass());
+  // FIXME: On AArch64, this depends on the type.
+  // Basically, the addressable offsets are up to 4095 * Ty.getSizeInBytes().
+  // and the offset has to be a multiple of the related size in bytes.
   if (TM->getOptLevel() != CodeGenOpt::None)
-    addPass(createGlobalMergePass(TM));
+    addPass(createGlobalMergePass(TM, 4095));
   if (TM->getOptLevel() != CodeGenOpt::None)
     addPass(createAArch64AddressTypePromotionPass());
 

Modified: llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp?rev=230245&r1=230244&r2=230245&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp Mon Feb 23 13:28:45 2015
@@ -1170,12 +1170,6 @@ ARMTargetLowering::createFastISel(Functi
   return ARM::createFastISel(funcInfo, libInfo);
 }
 
-/// getMaximalGlobalOffset - Returns the maximal possible offset which can
-/// be used for loads / stores from the global.
-unsigned ARMTargetLowering::getMaximalGlobalOffset() const {
-  return (Subtarget->isThumb1Only() ? 127 : 4095);
-}
-
 Sched::Preference ARMTargetLowering::getSchedulingPreference(SDNode *N) const {
   unsigned NumVals = N->getNumValues();
   if (!NumVals)

Modified: llvm/trunk/lib/Target/ARM/ARMISelLowering.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMISelLowering.h?rev=230245&r1=230244&r2=230245&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMISelLowering.h (original)
+++ llvm/trunk/lib/Target/ARM/ARMISelLowering.h Mon Feb 23 13:28:45 2015
@@ -353,10 +353,6 @@ namespace llvm {
     /// specified value type.
     const TargetRegisterClass *getRegClassFor(MVT VT) const override;
 
-    /// getMaximalGlobalOffset - Returns the maximal possible offset which can
-    /// be used for loads / stores from the global.
-    unsigned getMaximalGlobalOffset() const override;
-
     /// Returns true if a cast between SrcAS and DestAS is a noop.
     bool isNoopAddrSpaceCast(unsigned SrcAS, unsigned DestAS) const override {
       // Addrspacecasts are always noops.

Modified: llvm/trunk/lib/Target/ARM/ARMTargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMTargetMachine.cpp?rev=230245&r1=230244&r2=230245&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMTargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMTargetMachine.cpp Mon Feb 23 13:28:45 2015
@@ -326,7 +326,12 @@ void ARMPassConfig::addIRPasses() {
 
 bool ARMPassConfig::addPreISel() {
   if (TM->getOptLevel() != CodeGenOpt::None)
-    addPass(createGlobalMergePass(TM));
+    // FIXME: This is using the thumb1 only constant value for
+    // maximal global offset for merging globals. We may want
+    // to look into using the old value for non-thumb1 code of
+    // 4095 based on the TargetMachine, but this starts to become
+    // tricky when doing code gen per function.
+    addPass(createGlobalMergePass(TM, 127));
 
   return false;
 }





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