Add a new visitor for walking the uses of a pointer value.

[oota-llvm.git] / lib / Analysis / PtrUseVisitor.cpp

diff --git a/lib/Analysis/PtrUseVisitor.cpp b/lib/Analysis/PtrUseVisitor.cpp
new file mode 100644 (file)
index 0000000..b48e86e
--- /dev/null
+++ b/lib/Analysis/PtrUseVisitor.cpp
@@ -0,0 +1,58 @@
+//===- PtrUseVisitor.cpp - InstVisitors over a pointers uses --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// Implementation of the pointer use visitors.
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/PtrUseVisitor.h"
+
+using namespace llvm;
+
+void detail::PtrUseVisitorBase::enqueueUsers(Instruction &I) {
+  for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
+       UI != UE; ++UI) {
+    if (VisitedUses.insert(&UI.getUse())) {
+      UseToVisit NewU = {
+        UseToVisit::UseAndIsOffsetKnownPair(&UI.getUse(), IsOffsetKnown),
+        Offset
+      };
+      Worklist.push_back(llvm_move(NewU));
+    }
+  }
+}
+
+bool detail::PtrUseVisitorBase::adjustOffsetForGEP(GetElementPtrInst &GEPI) {
+  if (!IsOffsetKnown)
+    return false;
+
+  for (gep_type_iterator GTI = gep_type_begin(GEPI), GTE = gep_type_end(GEPI);
+       GTI != GTE; ++GTI) {
+    ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
+    if (!OpC)
+      return false;
+    if (OpC->isZero())
+      continue;
+
+    // Handle a struct index, which adds its field offset to the pointer.
+    if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+      unsigned ElementIdx = OpC->getZExtValue();
+      const StructLayout *SL = DL.getStructLayout(STy);
+      Offset += APInt(Offset.getBitWidth(),
+                         SL->getElementOffset(ElementIdx));
+      continue;
+    }
+
+    // For array or vector indices, scale the index by the size of the type.
+    APInt Index = OpC->getValue().sextOrTrunc(Offset.getBitWidth());
+    Offset += Index * APInt(Offset.getBitWidth(),
+                               DL.getTypeAllocSize(GTI.getIndexedType()));
+  }
+  return true;
+}