Teach isDereferenceablePointer to look through returned-argument functions

For functions which are known to return their argument,
isDereferenceableAndAlignedPointer can examine the argument value.

Differential Revision: http://reviews.llvm.org/D9384

llvm-svn: 275038

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/Loads.cpp b/llvm/lib/Analysis/Loads.cpp
index 309a1d95efb..75426b54195 100644
--- a/llvm/lib/Analysis/Loads.cpp
+++ b/llvm/lib/Analysis/Loads.cpp
@@ -101,6 +101,11 @@ static bool isDereferenceableAndAlignedPointer(
     return isDereferenceableAndAlignedPointer(ASC->getOperand(0), Align, Size,
                                               DL, CtxI, DT, Visited);
 
+  if (auto CS = ImmutableCallSite(V))
+    if (const Value *RV = CS.getReturnedArgOperand())
+      return isDereferenceableAndAlignedPointer(RV, Align, Size, DL, CtxI, DT,
+                                                Visited);
+
   // If we don't know, assume the worst.
   return false;
 }