[SCEV] Do not bother creating separate SCEVUnknown for unreachable nodes
Currently, SCEV creates SCEVUnknown for every node of unreachable code. If we
have a huge amounts of such code, we will be littering SE with these nodes. We could
just state that they all are undef and save some memory.
Differential Revision: https://reviews.llvm.org/D57567
Reviewed By: sanjoy
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353017 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index c554f9c..fcf6a2b 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -6144,7 +6144,7 @@
// to obey basic rules for definitions dominating uses which this
// analysis depends on.
if (!DT.isReachableFromEntry(I->getParent()))
- return getUnknown(V);
+ return getUnknown(UndefValue::get(V->getType()));
} else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
return getConstant(CI);
else if (isa<ConstantPointerNull>(V))
diff --git a/test/Analysis/ScalarEvolution/unreachable-code.ll b/test/Analysis/ScalarEvolution/unreachable-code.ll
index 51d9398..69a7e39 100644
--- a/test/Analysis/ScalarEvolution/unreachable-code.ll
+++ b/test/Analysis/ScalarEvolution/unreachable-code.ll
@@ -1,7 +1,7 @@
; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
; CHECK: %t = add i64 %t, 1
-; CHECK: --> %t
+; CHECK: --> undef
define void @foo() {
entry:
