From c565ec08ac19f3afa573f93fd4beac7af05244ae Mon Sep 17 00:00:00 2001
From: jbrodman <james.brodman@intel.com>
Date: Thu, 13 Nov 2014 07:23:00 -0800
Subject: [PATCH] Disable optimization to eliminate illegal results

---
 opt.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/opt.cpp b/opt.cpp
index ed975921..9afbd11c 100644
--- a/opt.cpp
+++ b/opt.cpp
@@ -1210,7 +1210,11 @@ InstructionSimplifyPass::simplifyBoolVec(llvm::Value *value) {
             zext->getOperand(0)->getType() == LLVMTypes::Int1VectorType)
             return zext->getOperand(0);
     }
-
+    /*
+      // This optimization has discernable benefit on the perf 
+      // suite on latest LLVM versions.
+      // On 3.4+ (maybe even older), it can result in illegal 
+      // operations, so it's being disabled.
     llvm::ICmpInst *icmp = llvm::dyn_cast<llvm::ICmpInst>(value);
     if (icmp != NULL) {
         // icmp(ne, {sext,zext}(foo), zeroinitializer) -> foo
@@ -1226,7 +1230,9 @@ InstructionSimplifyPass::simplifyBoolVec(llvm::Value *value) {
                     return zext->getOperand(0);
             }
         }
+
     }
+    */
     return NULL;
 }