Teach SCEV to look through returned-argument functions

When building SCEVs, if a function is known to return its argument, then we can
build the SCEV using the corresponding argument value.

Differential Revision: http://reviews.llvm.org/D9381

llvm-svn: 275037

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 9c1712ab771..2abbf348035 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -5225,6 +5225,13 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
     if (isa<Instruction>(U))
       return createNodeForSelectOrPHI(cast<Instruction>(U), U->getOperand(0),
                                       U->getOperand(1), U->getOperand(2));
+    break;
+
+  case Instruction::Call:
+  case Instruction::Invoke:
+    if (Value *RV = CallSite(U).getReturnedArgOperand())
+      return getSCEV(RV);
+    break;
   }
 
   return getUnknown(V);