NFC. Introduce Value::getPointerDerferecnceableBytes

Extract a part of isDereferenceableAndAlignedPointer functionality to Value::getPointerDerferecnceableBytes. Currently it's a NFC, but in future I'm going to accumulate all the logic about value dereferenceability in this function similarly to Value::getPointerAlignment function (D16144).

Reviewed By: reames

Differential Revision: http://reviews.llvm.org/D17572

llvm-svn: 267708

1 files changed, 34 insertions, 0 deletions

diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index 08b4936..fb8d00f 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -525,6 +525,40 @@ Value *Value::stripInBoundsOffsets() {
   return stripPointerCastsAndOffsets<PSK_InBounds>(this);
 }
 
+unsigned Value::getPointerDereferenceableBytes(bool &CanBeNull) const {
+  assert(getType()->isPointerTy() && "must be pointer");
+
+  unsigned DerefBytes = 0;
+  CanBeNull = false;
+  if (const Argument *A = dyn_cast<Argument>(this)) {
+    DerefBytes = A->getDereferenceableBytes();
+    if (DerefBytes == 0) {
+      DerefBytes = A->getDereferenceableOrNullBytes();
+      CanBeNull = true;
+    }
+  } else if (auto CS = ImmutableCallSite(this)) {
+    DerefBytes = CS.getDereferenceableBytes(0);
+    if (DerefBytes == 0) {
+      DerefBytes = CS.getDereferenceableOrNullBytes(0);
+      CanBeNull = true;
+    }
+  } else if (const LoadInst *LI = dyn_cast<LoadInst>(this)) {
+    if (MDNode *MD = LI->getMetadata(LLVMContext::MD_dereferenceable)) {
+      ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(0));
+      DerefBytes = CI->getLimitedValue();
+    }
+    if (DerefBytes == 0) {
+      if (MDNode *MD =
+              LI->getMetadata(LLVMContext::MD_dereferenceable_or_null)) {
+        ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(0));
+        DerefBytes = CI->getLimitedValue();
+      }
+      CanBeNull = true;
+    }
+  }
+  return DerefBytes;
+}
+
 unsigned Value::getPointerAlignment(const DataLayout &DL) const {
   assert(getType()->isPointerTy() && "must be pointer");