Lower static global into allocas. (#299)

lib/Transforms/Scalar/ScalarReplAggregatesHLSL.cpp

@@ -3527,7 +3527,7 @@ void PointerStatus::analyzePointer(const Value *V, PointerStatus &PS,
     if (const Instruction *I = dyn_cast<Instruction>(U)) {
       const Function *F = I->getParent()->getParent();
       if (!PS.AccessingFunction) {
-        F = PS.AccessingFunction;
+        PS.AccessingFunction = F;
       } else {
         if (F != PS.AccessingFunction)
           PS.HasMultipleAccessingFunctions = true;
@@ -3943,6 +3943,24 @@ public:
       }
     }
 
+    // Lower static global into allocas.
+    staticGVs.clear();
+    for (GlobalVariable &GV : M.globals()) {
+      bool isStaticGlobal =
+          HLModule::IsStaticGlobal(&GV) &&
+          GV.getType()->getAddressSpace() == DXIL::kDefaultAddrSpace;
+      bool noInitializer =
+          !GV.hasInitializer() || isa<UndefValue>(GV.getInitializer());
+      if (isStaticGlobal && noInitializer) {
+        staticGVs.emplace_back(&GV);
+      }
+    }
+
+    const DataLayout &DL = M.getDataLayout();
+    for (GlobalVariable *GV : staticGVs) {
+      lowerStaticGlobalIntoAlloca(GV, DL);
+    }
+
     return true;
   }
 
@@ -3977,6 +3995,7 @@ private:
     unsigned startArgIndex, llvm::StringMap<Type *> &semanticTypeMap);
   bool hasDynamicVectorIndexing(Value *V);
   void flattenGlobal(GlobalVariable *GV);
+  void lowerStaticGlobalIntoAlloca(GlobalVariable *GV, const DataLayout &DL);
   /// DeadInsts - Keep track of instructions we have made dead, so that
   /// we can remove them after we are done working.
   SmallVector<Value *, 32> DeadInsts;
@@ -4064,8 +4083,6 @@ void SROA_Parameter_HLSL::flattenGlobal(GlobalVariable *GV) {
   while (!WorkList.empty()) {
     GlobalVariable *EltGV = cast<GlobalVariable>(WorkList.front());
     WorkList.pop_front();
-    // Flat Global vector if no dynamic vector indexing.
-    bool bFlatVector = !hasDynamicVectorIndexing(EltGV);
 
     const bool bAllowReplace = true;
     if (SROA_Helper::LowerMemcpy(EltGV, /*annoation*/ nullptr, dxilTypeSys, DL,
@@ -4073,6 +4090,8 @@ void SROA_Parameter_HLSL::flattenGlobal(GlobalVariable *GV) {
       continue;
     }
 
+    // Flat Global vector if no dynamic vector indexing.
+    bool bFlatVector = !hasDynamicVectorIndexing(EltGV);
     std::vector<Value *> Elts;
     bool SROAed = SROA_Helper::DoScalarReplacement(
         EltGV, Elts, Builder, bFlatVector,
@@ -4118,6 +4137,23 @@ void SROA_Parameter_HLSL::flattenGlobal(GlobalVariable *GV) {
   }
 }
 
+void SROA_Parameter_HLSL::lowerStaticGlobalIntoAlloca(GlobalVariable *GV, const DataLayout &DL) {
+  DxilTypeSystem &typeSys = m_pHLModule->GetTypeSystem();
+  unsigned size = DL.getTypeAllocSize(GV->getType()->getElementType());
+  PointerStatus PS(size);
+  GV->removeDeadConstantUsers();
+  PS.analyzePointer(GV, PS, typeSys, /*bStructElt*/false);
+  // Make sure GV only used in one function.
+  if (PS.HasMultipleAccessingFunctions)
+    return;
+
+  Function *F = const_cast<Function*>(PS.AccessingFunction);
+  IRBuilder<> Builder(F->getEntryBlock().getFirstInsertionPt());
+  AllocaInst *AI = Builder.CreateAlloca(GV->getType()->getElementType());
+  ReplaceConstantWithInst(GV, AI, Builder);
+  GV->eraseFromParent();
+}
+
 static DxilFieldAnnotation &GetEltAnnotation(Type *Ty, unsigned idx, DxilFieldAnnotation &annotation, DxilTypeSystem &dxilTypeSys) {
   while (Ty->isArrayTy())
     Ty = Ty->getArrayElementType();

tools/clang/test/CodeGenHLSL/cbuffer_copy1.hlsl

@@ -0,0 +1,32 @@
+// RUN: %dxc -E not_main -T ps_6_0 %s | FileCheck %s
+
+// Make sure no load and store
+// CHECK-NOT: store float
+// CHECK-NOT: = load
+
+
+
+cbuffer T
+{
+	float4 a;
+	float4 b;
+}
+static struct X
+{
+	float4 a;
+	float4 b;
+} ST = { a, b};
+
+uint t;
+
+// Not use main as entry name to disable GlobalOpt.
+float4 not_main() : SV_Target
+{
+  float tmp = 0;
+  // Make big number of instructions to disable gvn.
+  [unroll]
+  for (uint i=0;i<100;i++)
+    tmp += sin(t+i);
+
+  return tmp + i + sin(ST.a) + ST.b;
+}

tools/clang/unittests/HLSL/CompilerTest.cpp

@@ -392,6 +392,7 @@ public:
   TEST_METHOD(CodeGenCast7)
   TEST_METHOD(CodeGenCbuf_init_static)
   TEST_METHOD(CodeGenCbufferCopy)
+  TEST_METHOD(CodeGenCbufferCopy1)
   TEST_METHOD(CodeGenCbufferCopy2)
   TEST_METHOD(CodeGenCbufferCopy3)
   TEST_METHOD(CodeGenCbufferCopy4)
@@ -2314,6 +2315,10 @@ TEST_F(CompilerTest, CodeGenCbufferCopy) {
   CodeGenTestCheck(L"..\\CodeGenHLSL\\cbuffer_copy.hlsl");
 }
 
+TEST_F(CompilerTest, CodeGenCbufferCopy1) {
+  CodeGenTestCheck(L"..\\CodeGenHLSL\\cbuffer_copy1.hlsl");
+}
+
 TEST_F(CompilerTest, CodeGenCbufferCopy2) {
   CodeGenTestCheck(L"..\\CodeGenHLSL\\cbuffer_copy2.hlsl");
 }