1 files changed, 91 insertions, 0 deletions
diff --git a/include/llvm/Analysis/Utils/Local.h b/include/llvm/Analysis/Utils/Local.h
new file mode 100644
index 000000000000..b4141bbff28d
--- /dev/null
+++ b/include/llvm/Analysis/Utils/Local.h
@@ -0,0 +1,91 @@
+//===- Local.h - Functions to perform local transformations -----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This family of functions perform various local transformations to the
+// program.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_UTILS_LOCAL_H
+#define LLVM_ANALYSIS_UTILS_LOCAL_H
+
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/GetElementPtrTypeIterator.h"
+
+namespace llvm {
+
+/// Given a getelementptr instruction/constantexpr, emit the code necessary to
+/// compute the offset from the base pointer (without adding in the base
+/// pointer). Return the result as a signed integer of intptr size.
+/// When NoAssumptions is true, no assumptions about index computation not
+/// overflowing is made.
+template <typename IRBuilderTy>
+Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &DL, User *GEP,
+                     bool NoAssumptions = false) {
+  GEPOperator *GEPOp = cast<GEPOperator>(GEP);
+  Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
+  Value *Result = Constant::getNullValue(IntPtrTy);
+
+  // If the GEP is inbounds, we know that none of the addressing operations will
+  // overflow in an unsigned sense.
+  bool isInBounds = GEPOp->isInBounds() && !NoAssumptions;
+
+  // Build a mask for high order bits.
+  unsigned IntPtrWidth = IntPtrTy->getScalarType()->getIntegerBitWidth();
+  uint64_t PtrSizeMask =
+      std::numeric_limits<uint64_t>::max() >> (64 - IntPtrWidth);
+
+  gep_type_iterator GTI = gep_type_begin(GEP);
+  for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
+       ++i, ++GTI) {
+    Value *Op = *i;
+    uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
+    if (Constant *OpC = dyn_cast<Constant>(Op)) {
+      if (OpC->isZeroValue())
+        continue;
+
+      // Handle a struct index, which adds its field offset to the pointer.
+      if (StructType *STy = GTI.getStructTypeOrNull()) {
+        if (OpC->getType()->isVectorTy())
+          OpC = OpC->getSplatValue();
+
+        uint64_t OpValue = cast<ConstantInt>(OpC)->getZExtValue();
+        Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
+
+        if (Size)
+          Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),
+                                      GEP->getName()+".offs");
+        continue;
+      }
+
+      Constant *Scale = ConstantInt::get(IntPtrTy, Size);
+      Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
+      Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/);
+      // Emit an add instruction.
+      Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
+      continue;
+    }
+    // Convert to correct type.
+    if (Op->getType() != IntPtrTy)
+      Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
+    if (Size != 1) {
+      // We'll let instcombine(mul) convert this to a shl if possible.
+      Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size),
+                              GEP->getName()+".idx", isInBounds /*NUW*/);
+    }
+
+    // Emit an add instruction.
+    Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
+  }
+  return Result;
+}
+
+}
+
+#endif // LLVM_TRANSFORMS_UTILS_LOCAL_H