From 684fe210a936216d5a2d0c01d29d7ad184441b03 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Thu, 23 Sep 2004 15:46:00 +0000
Subject: [PATCH] Implement select.ll:test16: fold   load (select C, X, null) 
 -> load X

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16499 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/InstructionCombining.cpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 462824d1f8f..f4edc4cb505 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -3071,6 +3071,20 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
         return new SelectInst(SI->getCondition(), V1, V2);
       }
 
+      // load (select (cond, null, P)) -> load P
+      if (Constant *C = dyn_cast<Constant>(SI->getOperand(1)))
+        if (C->isNullValue()) {
+          LI.setOperand(0, SI->getOperand(2));
+          return &LI;
+        }
+
+      // load (select (cond, P, null)) -> load P
+      if (Constant *C = dyn_cast<Constant>(SI->getOperand(2)))
+        if (C->isNullValue()) {
+          LI.setOperand(0, SI->getOperand(1));
+          return &LI;
+        }
+
     } else if (PHINode *PN = dyn_cast<PHINode>(Op)) {
       // load (phi (&V1, &V2, &V3))  --> phi(load &V1, load &V2, load &V3)
       bool Safe = PN->getParent() == LI.getParent();