Initial checkin of a pass to lower packed operations to scalars operations.

This also registers the pass with opt with a -lower-packed command line
option.

Patch contributed by Brad Jones.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15987 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/LowerPacked.cpp

@@ -0,0 +1,359 @@
+//===- LowerPacked.cpp -  Implementation of LowerPacked Transform ---------===//
+// 
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Brad Jones and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
+//
+// This file implements lowering Packed datatypes into more primitive
+// Packed datatypes, and finally to scalar operations.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Argument.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Function.h"
+#include "llvm/Instructions.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/InstVisitor.h"
+#include "Support/StringExtras.h"
+#include <algorithm>
+#include <map>
+#include <iostream>
+
+using namespace llvm;
+
+namespace {
+
+/// This pass converts packed operators to an
+/// equivalent operations on smaller packed data, to possibly
+/// scalar operations.  Currently it supports lowering
+/// to scalar operations.
+///
+/// @brief Transforms packed instructions to simpler instructions.
+///
+class LowerPacked : public FunctionPass, public InstVisitor<LowerPacked> {
+public:
+   /// @brief Lowers packed operations to scalar operations. 
+   /// @param F The fuction to process
+   virtual bool runOnFunction(Function &F);
+
+   /// @brief Lowers packed load instructions.
+   /// @param LI the load instruction to convert
+   void visitLoadInst(LoadInst& LI);
+
+   /// @brief Lowers packed store instructions.
+   /// @param SI the store instruction to convert
+   void visitStoreInst(StoreInst& SI);
+
+   /// @brief Lowers packed binary operations.
+   /// @param BO the binary operator to convert
+   void visitBinaryOperator(BinaryOperator& BO);
+
+   /// @brief Lowers packed select instructions.
+   /// @param SELI the select operator to convert
+   void visitSelectInst(SelectInst& SELI);
+
+   /// This function asserts if the instruction is a PackedType but
+   /// is handled by another function.
+   /// 
+   /// @brief Asserts if PackedType instruction is not handled elsewhere.
+   /// @param I the unhandled instruction
+   void visitInstruction(Instruction &I)
+   {
+      if(isa<PackedType>(I.getType())) {
+         std::cerr << "Unhandled Instruction with Packed ReturnType: " << 
+                      I << '\n';
+      }
+   }
+private:
+   /// @brief Retrieves lowered values for a packed value.
+   /// @param val the packed value
+   /// @return the lowered values
+   std::vector<Value*>& getValues(Value* val);
+
+   /// @brief Sets lowered values for a packed value.
+   /// @param val the packed value
+   /// @param values the corresponding lowered values
+   void setValues(Value* val,const std::vector<Value*>& values);
+
+   // Data Members
+   /// @brief whether we changed the function or not   
+   bool Changed;
+
+   /// @brief a map from old packed values to new smaller packed values
+   std::map<Value*,std::vector<Value*> > packedToScalarMap;
+
+   /// Instructions in the source program to get rid of
+   /// after we do a pass (the old packed instructions)
+   std::vector<Instruction*> instrsToRemove;
+}; 
+
+RegisterOpt<LowerPacked> 
+X("lower-packed", 
+  "lowers packed operations to operations on smaller packed datatypes");
+
+} // end namespace   
+
+// This function sets lowered values for a corresponding
+// packed value.  Note, in the case of a forward reference
+// getValues(Value*) will have already been called for 
+// the packed parameter.  This function will then replace 
+// all references in the in the function of the "dummy" 
+// value the previous getValues(Value*) call 
+// returned with actual references.
+void LowerPacked::setValues(Value* value,const std::vector<Value*>& values)
+{
+   std::map<Value*,std::vector<Value*> >::iterator it = 
+         packedToScalarMap.lower_bound(value);
+   if (it == packedToScalarMap.end() || it->first != value) {
+       // there was not a forward reference to this element
+       packedToScalarMap.insert(it,std::make_pair(value,values));
+   }
+   else {
+      // replace forward declarations with actual definitions
+      assert(it->second.size() == values.size() && 
+             "Error forward refences and actual definition differ in size");
+      for (unsigned i = 0, e = values.size(); i != e; ++i) {
+           // replace and get rid of old forward references
+           it->second[i]->replaceAllUsesWith(values[i]);
+           delete it->second[i];
+           it->second[i] = values[i];
+      }
+   }
+}
+
+// This function will examine the packed value parameter
+// and if it is a packed constant or a forward reference
+// properly create the lowered values needed.  Otherwise
+// it will simply retreive values from a  
+// setValues(Value*,const std::vector<Value*>&) 
+// call.  Failing both of these cases, it will abort
+// the program.
+std::vector<Value*>& LowerPacked::getValues(Value* value)
+{
+   assert(isa<PackedType>(value->getType()) &&
+          "Value must be PackedType");
+
+   // reject further processing if this one has
+   // already been handled
+   std::map<Value*,std::vector<Value*> >::iterator it = 
+      packedToScalarMap.lower_bound(value);
+   if (it != packedToScalarMap.end() && it->first == value) {
+       return it->second;
+   }
+
+   if (ConstantPacked* CP = dyn_cast<ConstantPacked>(value)) {
+       // non-zero constant case
+       std::vector<Value*> results;
+       results.reserve(CP->getNumOperands());
+       for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i) {
+          results.push_back(CP->getOperand(i));
+       }
+       return packedToScalarMap.insert(it,
+                                       std::make_pair(value,results))->second;
+   }
+   else if (ConstantAggregateZero* CAZ =
+            dyn_cast<ConstantAggregateZero>(value)) {
+       // zero constant 
+       const PackedType* PKT = cast<PackedType>(CAZ->getType());
+       std::vector<Value*> results;
+       results.reserve(PKT->getNumElements());
+   
+       Constant* C = Constant::getNullValue(PKT->getElementType());
+       for (unsigned i = 0, e = PKT->getNumElements(); i != e; ++i) {
+            results.push_back(C);
+       }
+       return packedToScalarMap.insert(it,
+                                       std::make_pair(value,results))->second;
+   }
+   else if (isa<Instruction>(value)) {
+       // foward reference
+       const PackedType* PKT = cast<PackedType>(value->getType());
+       std::vector<Value*> results;
+       results.reserve(PKT->getNumElements());
+   
+      for (unsigned i = 0, e = PKT->getNumElements(); i != e; ++i) {
+           results.push_back(new Argument(PKT->getElementType()));
+      }
+      return packedToScalarMap.insert(it,
+                                      std::make_pair(value,results))->second;
+   }
+   else {
+       // we don't know what it is, and we are trying to retrieve
+       // a value for it
+       assert(false && "Unhandled PackedType value");
+       abort();
+   }
+}
+
+void LowerPacked::visitLoadInst(LoadInst& LI)
+{
+   // Make sure what we are dealing with is a packed type
+   if (const PackedType* PKT = dyn_cast<PackedType>(LI.getType())) {
+       // Initialization, Idx is needed for getelementptr needed later
+       std::vector<Value*> Idx(2);
+       Idx[0] = ConstantUInt::get(Type::UIntTy,0);
+
+       ArrayType* AT = ArrayType::get(PKT->getContainedType(0),
+                                      PKT->getNumElements());
+       PointerType* APT = PointerType::get(AT);
+
+       // Cast the packed type to an array
+       Value* array = new CastInst(LI.getPointerOperand(),
+                                   APT,
+                                   LI.getName() + ".a",
+                                   &LI);
+
+       // Convert this load into num elements number of loads
+       std::vector<Value*> values;
+       values.reserve(PKT->getNumElements());
+
+       for (unsigned i = 0, e = PKT->getNumElements(); i != e; ++i) {
+            // Calculate the second index we will need
+            Idx[1] = ConstantUInt::get(Type::UIntTy,i);
+
+            // Get the pointer
+            Value* val = new GetElementPtrInst(array, 
+                                               Idx,
+                                               LI.getName() + 
+                                               ".ge." + utostr(i),
+                                               &LI);
+
+            // generate the new load and save the result in packedToScalar map
+            values.push_back(new LoadInst(val, 
+                             LI.getName()+"."+utostr(i),
+                             LI.isVolatile(),
+                             &LI));
+       }
+               
+       setValues(&LI,values);
+       Changed = true;
+       instrsToRemove.push_back(&LI);
+   }
+}
+
+void LowerPacked::visitBinaryOperator(BinaryOperator& BO)
+{
+   // Make sure both operands are PackedTypes
+   if (isa<PackedType>(BO.getOperand(0)->getType())) {
+       std::vector<Value*>& op0Vals = getValues(BO.getOperand(0));
+       std::vector<Value*>& op1Vals = getValues(BO.getOperand(1));
+       std::vector<Value*> result;
+       assert((op0Vals.size() == op1Vals.size()) &&
+              "The two packed operand to scalar maps must be equal in size.");
+
+       result.reserve(op0Vals.size());
+   
+       // generate the new binary op and save the result
+       for (unsigned i = 0; i != op0Vals.size(); ++i) {
+            result.push_back(BinaryOperator::create(BO.getOpcode(), 
+                                                    op0Vals[i], 
+                                                    op1Vals[i],
+                                                    BO.getName() + 
+                                                    "." + utostr(i),
+                                                    &BO));
+       }
+
+       setValues(&BO,result);
+       Changed = true;
+       instrsToRemove.push_back(&BO);
+   }
+}
+
+void LowerPacked::visitStoreInst(StoreInst& SI)
+{
+   if (const PackedType* PKT = 
+       dyn_cast<PackedType>(SI.getOperand(0)->getType())) {
+       // We will need this for getelementptr
+       std::vector<Value*> Idx(2);
+       Idx[0] = ConstantUInt::get(Type::UIntTy,0);
+         
+       ArrayType* AT = ArrayType::get(PKT->getContainedType(0),
+                                      PKT->getNumElements());
+       PointerType* APT = PointerType::get(AT);
+
+       // cast the packed to an array type
+       Value* array = new CastInst(SI.getPointerOperand(),
+                                   APT,
+                                   "store.ge.a.",
+                                   &SI);
+       std::vector<Value*>& values = getValues(SI.getOperand(0));
+      
+       assert((values.size() == PKT->getNumElements()) &&
+              "Scalar must have the same number of elements as Packed Type");
+
+       for (unsigned i = 0, e = PKT->getNumElements(); i != e; ++i) {
+            // Generate the indices for getelementptr
+            Idx[1] = ConstantUInt::get(Type::UIntTy,i);
+            Value* val = new GetElementPtrInst(array, 
+                                               Idx,
+                                               "store.ge." +
+                                               utostr(i) + ".",
+                                               &SI);
+            new StoreInst(values[i], val, SI.isVolatile(),&SI);
+       }
+                 
+       Changed = true;
+       instrsToRemove.push_back(&SI);
+   }
+}
+
+void LowerPacked::visitSelectInst(SelectInst& SELI)
+{
+   // Make sure both operands are PackedTypes
+   if (isa<PackedType>(SELI.getType())) {
+       std::vector<Value*>& op0Vals = getValues(SELI.getTrueValue());
+       std::vector<Value*>& op1Vals = getValues(SELI.getFalseValue());
+       std::vector<Value*> result;
+
+      assert((op0Vals.size() == op1Vals.size()) &&
+             "The two packed operand to scalar maps must be equal in size.");
+
+      for (unsigned i = 0; i != op0Vals.size(); ++i) {
+           result.push_back(new SelectInst(SELI.getCondition(),
+                                           op0Vals[i], 
+                                           op1Vals[i],
+                                           SELI.getName()+ "." + utostr(i),
+                                           &SELI));
+      }
+   
+      setValues(&SELI,result);
+      Changed = true;
+      instrsToRemove.push_back(&SELI);
+   }
+}
+
+bool LowerPacked::runOnFunction(Function& F)
+{
+   // initialize
+   Changed = false; 
+  
+   // Does three passes:
+   // Pass 1) Converts Packed Operations to 
+   //         new Packed Operations on smaller
+   //         datatypes
+   visit(F);
+  
+   // Pass 2) Drop all references
+   std::for_each(instrsToRemove.begin(),
+                 instrsToRemove.end(),
+                 std::mem_fun(&Instruction::dropAllReferences));
+
+   // Pass 3) Delete the Instructions to remove aka packed instructions
+   for (std::vector<Instruction*>::iterator i = instrsToRemove.begin(), 
+                                            e = instrsToRemove.end(); 
+        i != e; ++i) {
+        (*i)->getParent()->getInstList().erase(*i);   
+   }
+
+   // clean-up
+   packedToScalarMap.clear();
+   instrsToRemove.clear();
+
+   return Changed;
+}
+