Add new Pass infrastructure and some examples
llvm-svn: 836
diff --git a/llvm/lib/Transforms/Scalar/LowerAllocations.cpp b/llvm/lib/Transforms/Scalar/LowerAllocations.cpp
new file mode 100644
index 0000000..ba78ce1
--- /dev/null
+++ b/llvm/lib/Transforms/Scalar/LowerAllocations.cpp
@@ -0,0 +1,121 @@
+//===- llvm/Transforms/LowerAllocations.h - Remove Malloc & Free Insts ------=//
+//
+// This file implements a pass that lowers malloc and free instructions to
+// calls to %malloc & %free functions. This transformation is a target
+// dependant tranformation because we depend on the size of data types and
+// alignment constraints.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/LowerAllocations.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/iMemory.h"
+#include "llvm/iOther.h"
+#include "llvm/SymbolTable.h"
+
+// doPassInitialization - For the lower allocations pass, this ensures that a
+// module contains a declaration for a malloc and a free function.
+//
+// This function is always successful.
+//
+bool LowerAllocations::doPassInitializationVirt(Module *M) {
+ const MethodType *MallocType =
+ MethodType::get(PointerType::get(Type::UByteTy),
+ vector<const Type*>(1, Type::UIntTy), false);
+
+ SymbolTable *SymTab = M->getSymbolTableSure();
+
+ // Check for a definition of malloc
+ if (Value *V = SymTab->lookup(PointerType::get(MallocType), "malloc")) {
+ MallocMeth = cast<Method>(V); // Yup, got it
+ } else { // Nope, add one
+ M->getMethodList().push_back(MallocMeth = new Method(MallocType, "malloc"));
+ }
+
+ const MethodType *FreeType =
+ MethodType::get(Type::VoidTy,
+ vector<const Type*>(1, PointerType::get(Type::UByteTy)),
+ false);
+
+ // Check for a definition of free
+ if (Value *V = SymTab->lookup(PointerType::get(FreeType), "free")) {
+ FreeMeth = cast<Method>(V); // Yup, got it
+ } else { // Nope, add one
+ M->getMethodList().push_back(FreeMeth = new Method(FreeType, "free"));
+ }
+
+ return false; // Always successful
+}
+
+// doPerMethodWork - This method does the actual work of converting
+// instructions over, assuming that the pass has already been initialized.
+//
+bool LowerAllocations::doPerMethodWorkVirt(Method *M) {
+ assert(MallocMeth && FreeMeth && M && "Pass not initialized!");
+
+ // Loop over all of the instructions, looking for malloc or free instructions
+ for (Method::iterator BBI = M->begin(), BBE = M->end(); BBI != BBE; ++BBI) {
+ BasicBlock *BB = *BBI;
+ for (unsigned i = 0; i < BB->size(); ++i) {
+ BasicBlock::InstListType &BBIL = BB->getInstList();
+ if (MallocInst *MI = dyn_cast<MallocInst>(*(BBIL.begin()+i))) {
+ BBIL.remove(BBIL.begin()+i); // remove the malloc instr...
+
+ const Type *AllocTy = cast<PointerType>(MI->getType())->getValueType();
+
+ // If the user is allocating an unsized array with a dynamic size arg,
+ // start by getting the size of one element.
+ //
+ if (const ArrayType *ATy = dyn_cast<ArrayType>(AllocTy))
+ if (ATy->isUnsized()) AllocTy = ATy->getElementType();
+
+ // Get the number of bytes to be allocated for one element of the
+ // requested type...
+ unsigned Size = DataLayout.getTypeSize(AllocTy);
+
+ // malloc(type) becomes sbyte *malloc(constint)
+ Value *MallocArg = ConstPoolUInt::get(Type::UIntTy, Size);
+ if (MI->getNumOperands() && Size == 1) {
+ MallocArg = MI->getOperand(0); // Operand * 1 = Operand
+ } else if (MI->getNumOperands()) {
+ // Multiply it by the array size if neccesary...
+ MallocArg = BinaryOperator::create(Instruction::Mul,MI->getOperand(0),
+ MallocArg);
+ BBIL.insert(BBIL.begin()+i++, cast<Instruction>(MallocArg));
+ }
+
+ // Create the call to Malloc...
+ CallInst *MCall = new CallInst(MallocMeth,
+ vector<Value*>(1, MallocArg));
+ BBIL.insert(BBIL.begin()+i, MCall);
+
+ // Create a cast instruction to convert to the right type...
+ CastInst *MCast = new CastInst(MCall, MI->getType());
+ BBIL.insert(BBIL.begin()+i+1, MCast);
+
+ // Replace all uses of the old malloc inst with the cast inst
+ MI->replaceAllUsesWith(MCast);
+ delete MI; // Delete the malloc inst
+ } else if (FreeInst *FI = dyn_cast<FreeInst>(*(BBIL.begin()+i))) {
+ BBIL.remove(BB->getInstList().begin()+i);
+
+ // Cast the argument to free into a ubyte*...
+ CastInst *MCast = new CastInst(FI->getOperand(0),
+ PointerType::get(Type::UByteTy));
+ BBIL.insert(BBIL.begin()+i, MCast);
+
+ // Insert a call to the free function...
+ CallInst *FCall = new CallInst(FreeMeth,
+ vector<Value*>(1, MCast));
+ BBIL.insert(BBIL.begin()+i+1, FCall);
+
+ // Delete the old free instruction
+ delete FI;
+ }
+ }
+ }
+
+ return false; // Always successful
+}
+