[llvm-commits] [llvm] r131073 - in /llvm/trunk/lib/CodeGen: LiveDebugVariables.cpp MachineInstr.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Sun May  8 14:21:08 2011
New Revision: 131073

URL: http://llvm.org/viewvc/llvm-project?rev=131073&view=rev
Log:
Remove an assertion to fix PR9872.

It can happen that a live debug variable is the last use of a sub-register, and
the register allocator will pick a larger register class for the virtual
register.  If the allocated register doesn't support the sub-register index,
just use %noreg for the debug variables instead of asserting.

In PR9872, a debug variable ends up in the sub_8bit_hi part of a GR32_ABCD
register. The register is split and one part is inflated to GR32 and assigned
%ESI because there are no more normal uses of sub_8bit_hi.

Since %ESI doesn't have that sub-register, substPhysReg asserted. Now it will
simply insert a %noreg instead, and the debug variable will be marked
unavailable in that range.

We don't currently have a way of saying: !"value" is in bits 8-15 of %ESI, I
don't know if DWARF even supports that.

Modified:
    llvm/trunk/lib/CodeGen/LiveDebugVariables.cpp
    llvm/trunk/lib/CodeGen/MachineInstr.cpp

Modified: llvm/trunk/lib/CodeGen/LiveDebugVariables.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveDebugVariables.cpp?rev=131073&r1=131072&r2=131073&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveDebugVariables.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveDebugVariables.cpp Sun May  8 14:21:08 2011
@@ -840,6 +840,9 @@
     unsigned VirtReg = Loc.getReg();
     if (VRM.isAssignedReg(VirtReg) &&
         TargetRegisterInfo::isPhysicalRegister(VRM.getPhys(VirtReg))) {
+      // This can create a %noreg operand in rare cases when the sub-register
+      // index is no longer available. That means the user value is in a
+      // non-existent sub-register, and %noreg is exactly what we want.
       Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
     } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT &&
                VRM.isSpillSlotUsed(VRM.getStackSlot(VirtReg))) {
@@ -942,6 +945,7 @@
   DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
   const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
+    DEBUG(userValues[i]->print(dbgs(), &MF->getTarget()));
     userValues[i]->rewriteLocations(*VRM, *TRI);
     userValues[i]->emitDebugValues(VRM, *LIS, *TII);
   }

Modified: llvm/trunk/lib/CodeGen/MachineInstr.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineInstr.cpp?rev=131073&r1=131072&r2=131073&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineInstr.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineInstr.cpp Sun May  8 14:21:08 2011
@@ -125,7 +125,8 @@
   assert(TargetRegisterInfo::isPhysicalRegister(Reg));
   if (getSubReg()) {
     Reg = TRI.getSubReg(Reg, getSubReg());
-    assert(Reg && "Invalid SubReg for physical register");
+    // Note that getSubReg() may return 0 if the sub-register doesn't exist.
+    // That won't happen in legal code.
     setSubReg(0);
   }
   setReg(Reg);