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

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 8304e2e..56cb2cc 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();