Refactor some methods to look through bitcasts and GEPs on pointers into

a common collection of methods on Value, and share their implementation.
We had two variations in two different places already, and I need the
third variation for inline cost estimation.

Reviewed by Duncan Sands on IRC, but further comments here welcome.

llvm-svn: 152490

1 files changed, 42 insertions, 6 deletions

diff --git a/llvm/lib/VMCore/Value.cpp b/llvm/lib/VMCore/Value.cpp
index 207c06d2231..40b2d95e3d0 100644
--- a/llvm/lib/VMCore/Value.cpp
+++ b/llvm/lib/VMCore/Value.cpp
@@ -317,20 +317,43 @@ void Value::replaceAllUsesWith(Value *New) {
     BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
 }
 
-Value *Value::stripPointerCasts() {
-  if (!getType()->isPointerTy())
-    return this;
+namespace {
+// Various metrics for how much to strip off of pointers.
+enum PointerStripKind {
+  PSK_ZeroIndices,
+  PSK_ConstantIndices,
+  PSK_InBounds,
+  PSK_All
+};
+
+template <PointerStripKind StripKind>
+static Value *stripPointerCastsAndOffsets(Value *V) {
+  if (!V->getType()->isPointerTy())
+    return V;
 
   // Even though we don't look through PHI nodes, we could be called on an
   // instruction in an unreachable block, which may be on a cycle.
   SmallPtrSet<Value *, 4> Visited;
 
-  Value *V = this;
   Visited.insert(V);
   do {
     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
-      if (!GEP->hasAllZeroIndices())
-        return V;
+      switch (StripKind) {
+      case PSK_ZeroIndices:
+        if (!GEP->hasAllZeroIndices())
+          return V;
+        break;
+      case PSK_ConstantIndices:
+        if (!GEP->hasAllConstantIndices())
+          return V;
+        break;
+      case PSK_InBounds:
+        if (!GEP->isInBounds())
+          return V;
+        break;
+      case PSK_All:
+        break;
+      }
       V = GEP->getPointerOperand();
     } else if (Operator::getOpcode(V) == Instruction::BitCast) {
       V = cast<Operator>(V)->getOperand(0);
@@ -346,6 +369,19 @@ Value *Value::stripPointerCasts() {
 
   return V;
 }
+} // namespace
+
+Value *Value::stripPointerCasts() {
+  return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
+}
+
+Value *Value::stripConstantOffsets() {
+  return stripPointerCastsAndOffsets<PSK_ConstantIndices>(this);
+}
+
+Value *Value::stripInBoundsOffsets() {
+  return stripPointerCastsAndOffsets<PSK_InBounds>(this);
+}
 
 /// isDereferenceablePointer - Test if this value is always a pointer to
 /// allocated and suitably aligned memory for a simple load or store.