From: Torok Edwin <edwintorok@gmail.com>
Date: Fri, 29 May 2009 09:46:03 +0000 (+0000)
Subject: Add a DEBUG() output to GVN that prints the instruction clobbering a load.
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=3f3c6d4e5be4b916ed9d30ba85a428e01a65d8c5;p=oota-llvm.git

Add a DEBUG() output to GVN that prints the instruction clobbering a load.
This is useful when trying to figure out why GVN didn't eliminate redundant
loads.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72565 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index 222320f5257..946c33eea44 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -1158,8 +1158,18 @@ bool GVN::processLoad(LoadInst *L, SmallVectorImpl<Instruction*> &toErase) {
   MemDepResult dep = MD->getDependency(L);
   
   // If the value isn't available, don't do anything!
-  if (dep.isClobber())
+  if (dep.isClobber()) {
+    DEBUG(
+      // fast print dep, using operator<< on instruction would be too slow
+      DOUT << "GVN: load ";
+      WriteAsOperand(*DOUT.stream(), L);
+      Instruction *I = dep.getInst();
+      DOUT << " is clobbered by " << I->getOpcodeName() << " instruction ";
+      WriteAsOperand(*DOUT.stream(), I, false);
+      DOUT << "\n";
+    );
     return false;
+  }
 
   // If it is defined in another block, try harder.
   if (dep.isNonLocal())