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diff gen/passes/GarbageCollect2Stack.cpp @ 1317:4099548c80e0

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Allocate objects on the stack if they (a) don't have a destructor, and (b) don't override the delete operator (on top of the regular conditions for stack allocation that also apply to arrays, structs, etc.). The "no destructor" clause is not strictly necessary, but calling them at the right time would be tricky to say the least; it would involve, among other things, "manually" inserting a try-finally block around anything that might throw exceptions not caught in the current function. Note: objects with custom new operators are automatically ignored because they don't use the regular allocation runtime call, so there's no need to pay special attention to them.
author Frits van Bommel <fvbommel wxs.nl>
date Sat, 09 May 2009 00:50:15 +0200
parents 8c65217be813
children c21a6654cce2
line wrap: on
line diff
--- a/gen/passes/GarbageCollect2Stack.cpp	Fri May 08 16:00:44 2009 +0200
+++ b/gen/passes/GarbageCollect2Stack.cpp	Sat May 09 00:50:15 2009 +0200
@@ -180,6 +180,53 @@
             return alloca;
         }
     };
+    
+    // FunctionInfo for _d_allocclass
+    class AllocClassFI : public FunctionInfo {
+        public:
+        virtual bool analyze(CallSite CS, const Analysis& A) {
+            // This call contains no TypeInfo parameter, so don't call the
+            // base class implementation here...
+            if (CS.arg_size() != 1)
+                return false;
+            Value* arg = CS.getArgument(0)->stripPointerCasts();
+            GlobalVariable* ClassInfo = dyn_cast<GlobalVariable>(arg);
+            if (!ClassInfo)
+                return false;
+            
+            std::string metaname = CD_PREFIX;
+            metaname.append(ClassInfo->getNameStart(), ClassInfo->getNameEnd());
+            
+            GlobalVariable* global = A.M.getGlobalVariable(metaname);
+            if (!global || !global->hasInitializer())
+                return false;
+            
+            MDNode* node = dyn_cast<MDNode>(global->getInitializer());
+            if (!node || node->getNumOperands() != CD_NumFields)
+                return false;
+            
+            // Inserting destructor calls is not implemented yet, so classes
+            // with destructors are ignored for now.
+            Constant* hasDestructor = dyn_cast<Constant>(node->getOperand(CD_Finalize));
+            // We can't stack-allocate if the class has a custom deallocator
+            // (Custom allocators don't get turned into this runtime call, so
+            // those can be ignored)
+            Constant* hasCustomDelete = dyn_cast<Constant>(node->getOperand(CD_CustomDelete));
+            if (hasDestructor == NULL || hasCustomDelete == NULL)
+                return false;
+            
+            if (ConstantExpr::getOr(hasDestructor, hasCustomDelete)
+                    != ConstantInt::getFalse())
+                return false;
+            
+            Ty = node->getOperand(CD_BodyType)->getType();
+            return true;
+        }
+        
+        // The default promote() should be fine.
+        
+        AllocClassFI() : FunctionInfo(-1, true) {}
+    };
 }
 
 
@@ -197,6 +244,7 @@
         FunctionInfo AllocMemoryT;
         ArrayFI NewArrayVT;
         ArrayFI NewArrayT;
+        AllocClassFI AllocClass;
         
     public:
         static char ID; // Pass identification
@@ -233,6 +281,7 @@
     KnownFunctions["_d_allocmemoryT"] = &AllocMemoryT;
     KnownFunctions["_d_newarrayvT"] = &NewArrayVT;
     KnownFunctions["_d_newarrayT"] = &NewArrayT;
+    KnownFunctions["_d_allocclass"] = &AllocClass;
 }
 
 static void RemoveCall(Instruction* Inst) {