commit 7806c0778f22552ebe6711f3dc43887dc6097bfc
author Jakob Stoklund Olesen <stoklund@2pi.dk> Sat Jun 23 02:23:00 2012 +0000
committer Jakob Stoklund Olesen <stoklund@2pi.dk> Sat Jun 23 02:23:00 2012 +0000
tree 2eb6e70baa395b80e298fba8b94c4e131b73e3c2
parent ce0a5cda8aa547d5219da70a68bef40d5ed8392c

Teach LiveVariables to handle <undef> operands.

It's simple: Don't treat <undef> operands as uses, and don't assume a
virtual register has a defining instruction unless a real use has been
seen.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159061 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LiveVariables.cpp

diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
index acf986c..348ed3a 100644
--- a/lib/CodeGen/LiveVariables.cpp
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -573,7 +573,8 @@
         unsigned MOReg = MO.getReg();
         if (MO.isUse()) {
           MO.setIsKill(false);
-          UseRegs.push_back(MOReg);
+          if (MO.readsReg())
+            UseRegs.push_back(MOReg);
         } else /*MO.isDef()*/ {
           MO.setIsDead(false);
           DefRegs.push_back(MOReg);
@@ -729,8 +730,9 @@
     for (MachineBasicBlock::const_iterator BBI = I->begin(), BBE = I->end();
          BBI != BBE && BBI->isPHI(); ++BBI)
       for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2)
-        PHIVarInfo[BBI->getOperand(i + 1).getMBB()->getNumber()]
-          .push_back(BBI->getOperand(i).getReg());
+        if (BBI->getOperand(i).readsReg())
+          PHIVarInfo[BBI->getOperand(i + 1).getMBB()->getNumber()]
+            .push_back(BBI->getOperand(i).getReg());
 }
 
 bool LiveVariables::VarInfo::isLiveIn(const MachineBasicBlock &MBB,