Fix PR6520. An earlyclobber physreg must not be allocated to anything else.

llvm-svn: 103133

1 files changed, 12 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/RegAllocLocal.cpp b/llvm/lib/CodeGen/RegAllocLocal.cpp
index 94456d14385..a3d2f9d2c2e 100644
--- a/llvm/lib/CodeGen/RegAllocLocal.cpp
+++ b/llvm/lib/CodeGen/RegAllocLocal.cpp
@@ -843,8 +843,18 @@ void RALocal::AllocateBasicBlock(MachineBasicBlock &MBB) {
     SmallVector<unsigned, 8> Kills;
     for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
       MachineOperand &MO = MI->getOperand(i);
-      if (!MO.isReg() || !MO.isKill()) continue;
-      
+      if (!MO.isReg()) continue;
+      unsigned Reg = MO.getReg();
+      if (!Reg) continue;
+
+      // Avoid allocating assigned early clobbers below.
+      if (MO.isEarlyClobber() && TargetRegisterInfo::isPhysicalRegister(Reg)) {
+        spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in reg
+        PhysRegsUsed[Reg] = 0;            // It is free and reserved now
+        AddToPhysRegsUseOrder(Reg);
+      }
+
+      if (!MO.isKill()) continue;
       if (!MO.isImplicit())
         Kills.push_back(MO.getReg());
       else if (!isReadModWriteImplicitKill(MI, MO.getReg()))