Move this file from lib/Transforms/Scalar
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17544 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/SparcV9/DecomposeMultiDimRefs.cpp b/lib/Target/SparcV9/DecomposeMultiDimRefs.cpp
new file mode 100644
index 0000000..40e1be5
--- /dev/null
+++ b/lib/Target/SparcV9/DecomposeMultiDimRefs.cpp
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+//===- 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;
+}
+