[llvm-commits] CVS: llvm/lib/Target/SparcV9/DecomposeMultiDimRefs.cpp

[Chris Lattner]

Changes in directory llvm/lib/Target/SparcV9:

DecomposeMultiDimRefs.cpp added (r1.1)
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Log message:

Move this file from lib/Transforms/Scalar


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Diffs of the changes:  (+136 -0)

Index: llvm/lib/Target/SparcV9/DecomposeMultiDimRefs.cpp
diff -c /dev/null llvm/lib/Target/SparcV9/DecomposeMultiDimRefs.cpp:1.1
*** /dev/null	Sat Nov  6 18:39:19 2004
--- llvm/lib/Target/SparcV9/DecomposeMultiDimRefs.cpp	Sat Nov  6 18:39:09 2004
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*** 0 ****
--- 1,136 ----
+ //===- llvm/Transforms/DecomposeMultiDimRefs.cpp - Lower array refs to 1D -===//
+ // 
+ //                     The LLVM Compiler Infrastructure
+ //
+ // This file was developed by the LLVM research group and is distributed under
+ // the University of Illinois Open Source License. See LICENSE.TXT for details.
+ // 
+ //===----------------------------------------------------------------------===//
+ //
+ // DecomposeMultiDimRefs - Convert multi-dimensional references consisting of
+ // any combination of 2 or more array and structure indices into a sequence of
+ // instructions (using getelementpr and cast) so that each instruction has at
+ // most one index (except structure references, which need an extra leading
+ // index of [0]).
+ //
+ //===----------------------------------------------------------------------===//
+ 
+ #include "llvm/Transforms/Scalar.h"
+ #include "llvm/DerivedTypes.h"
+ #include "llvm/Constants.h"
+ #include "llvm/Constant.h"
+ #include "llvm/Instructions.h"
+ #include "llvm/BasicBlock.h"
+ #include "llvm/Pass.h"
+ #include "llvm/ADT/Statistic.h"
+ #include "llvm/Support/Debug.h"
+ using namespace llvm;
+ 
+ namespace {
+   Statistic<> NumAdded("lowerrefs", "# of getelementptr instructions added");
+ 
+   struct DecomposePass : public BasicBlockPass {
+     virtual bool runOnBasicBlock(BasicBlock &BB);
+   };
+   RegisterOpt<DecomposePass> X("lowerrefs", "Decompose multi-dimensional "
+                                "structure/array references");
+ }
+ 
+ // runOnBasicBlock - Entry point for array or structure references with multiple
+ // indices.
+ //
+ bool DecomposePass::runOnBasicBlock(BasicBlock &BB) {
+   bool changed = false;
+   for (BasicBlock::iterator II = BB.begin(); II != BB.end(); )
+     if (GetElementPtrInst *gep = dyn_cast<GetElementPtrInst>(II++)) // pre-inc
+       if (gep->getNumIndices() >= 2)
+         changed |= DecomposeArrayRef(gep); // always modifies II
+   return changed;
+ }
+ 
+ FunctionPass *llvm::createDecomposeMultiDimRefsPass() {
+   return new DecomposePass();
+ }
+ 
+ static inline bool isZeroConst (Value *V) {
+   return isa<Constant> (V) && (cast<Constant>(V)->isNullValue());
+ }
+ 
+ // Function: DecomposeArrayRef()
+ //  
+ // For any GetElementPtrInst with 2 or more array and structure indices:
+ // 
+ //      opCode CompositeType* P, [uint|ubyte] idx1, ..., [uint|ubyte] idxN
+ // 
+ // this function generates the following sequence:
+ // 
+ //      ptr1   = getElementPtr P,         idx1
+ //      ptr2   = getElementPtr ptr1,   0, idx2
+ //      ...
+ //      ptrN-1 = getElementPtr ptrN-2, 0, idxN-1
+ //      opCode                 ptrN-1, 0, idxN  // New-MAI
+ // 
+ // Then it replaces the original instruction with this sequence,
+ // and replaces all uses of the original instruction with New-MAI.
+ // If idx1 is 0, we simply omit the first getElementPtr instruction.
+ // 
+ // On return: BBI points to the instruction after the current one
+ //            (whether or not *BBI was replaced).
+ // 
+ // Return value: true if the instruction was replaced; false otherwise.
+ // 
+ bool llvm::DecomposeArrayRef(GetElementPtrInst* GEP) {
+   if (GEP->getNumIndices() < 2
+       || (GEP->getNumIndices() == 2
+           && isZeroConst(GEP->getOperand(1)))) {
+     DEBUG (std::cerr << "DecomposeArrayRef: Skipping " << *GEP);
+     return false;
+   } else {
+     DEBUG (std::cerr << "DecomposeArrayRef: Decomposing " << *GEP);
+   }
+ 
+   BasicBlock *BB = GEP->getParent();
+   Value *LastPtr = GEP->getPointerOperand();
+   Instruction *InsertPoint = GEP->getNext(); // Insert before the next insn
+ 
+   // Process each index except the last one.
+   User::const_op_iterator OI = GEP->idx_begin(), OE = GEP->idx_end();
+   for (; OI+1 != OE; ++OI) {
+     std::vector<Value*> Indices;
+     
+     // If this is the first index and is 0, skip it and move on!
+     if (OI == GEP->idx_begin()) {
+       if (isZeroConst (*OI))
+         continue;
+     }
+     else // Not the first index: include initial [0] to deref the last ptr
+       Indices.push_back(Constant::getNullValue(Type::LongTy));
+ 
+     Indices.push_back(*OI);
+ 
+     // New Instruction: nextPtr1 = GetElementPtr LastPtr, Indices
+     LastPtr = new GetElementPtrInst(LastPtr, Indices, "ptr1", InsertPoint);
+     ++NumAdded;
+   }
+ 
+   // Now create a new instruction to replace the original one
+   //
+   const PointerType *PtrTy = cast<PointerType>(LastPtr->getType());
+ 
+   // Get the final index vector, including an initial [0] as before.
+   std::vector<Value*> Indices;
+   Indices.push_back(Constant::getNullValue(Type::LongTy));
+   Indices.push_back(*OI);
+ 
+   Value *NewVal = new GetElementPtrInst(LastPtr, Indices, GEP->getName(),
+                                         InsertPoint);
+ 
+   // Replace all uses of the old instruction with the new
+   GEP->replaceAllUsesWith(NewVal);
+ 
+   // Now remove and delete the old instruction...
+   BB->getInstList().erase(GEP);
+ 
+   return true;
+ }
+