From c76d80342e229a86bf3f780c797e29d197363bc4 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Sun, 7 Mar 2004 22:16:24 +0000
Subject: [PATCH] Since 'load null' is undefined, we can make it do whatever we
 want.  Returning a zero value is the most likely way to cause further
 simplification, so we do it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12197 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/SCCP.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 8304e2e823b..56cb2cc7701 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -713,6 +713,12 @@ void SCCP::visitLoadInst(LoadInst &I) {
   if (PtrVal.isUndefined()) return;   // The pointer is not resolved yet!
   if (PtrVal.isConstant() && !I.isVolatile()) {
     Value *Ptr = PtrVal.getConstant();
+    if (isa<ConstantPointerNull>(Ptr)) {
+      // load null -> null
+      markConstant(IV, &I, Constant::getNullValue(I.getType()));
+      return;
+    }
+      
     if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Ptr))
       Ptr = CPR->getValue();