Subzero: Fix a couple of debugging tools.

1. Regalloc dump output was displaying status updates for the wrong variable in some cases.

2. getPhysicalRegister() creates a variable for referring to a specific physical register for low-level purposes, such as the stack pointer, or the frame pointer, or a pushed/popped callee-save register.  We change its behavior so that all such physical registers do not have their liveness tracked/validated, not just the stack pointer.

For #2, the original behavior was causing a liveness validation failure if a function had a single basic block and used callee-save registers, and the -asm-verbose flag was used.  This is because -asm-verbose runs a final liveness pass after the prolog/epilog are generated, and the initial callee-save register pushes would make it look like single-basic-block variables are live coming into a basic block, which is a hallmark of a liveness problem.

BUG= none
R=jpp@chromium.org

Review URL: https://codereview.chromium.org/1353923004 .

src/IceTargetLoweringARM32.cpp

diff --git a/src/IceTargetLoweringARM32.cpp b/src/IceTargetLoweringARM32.cpp
index 0fe62e4..682048a 100644
--- a/src/IceTargetLoweringARM32.cpp
+++ b/src/IceTargetLoweringARM32.cpp
@@ -389,12 +389,12 @@
     Reg = Func->makeVariable(Ty);
     Reg->setRegNum(RegNum);
     PhysicalRegisters[Ty][RegNum] = Reg;
-    // Specially mark SP and LR as an "argument" so that it is considered live
-    // upon function entry.
-    if (RegNum == RegARM32::Reg_sp || RegNum == RegARM32::Reg_lr) {
-      Func->addImplicitArg(Reg);
-      Reg->setIgnoreLiveness();
-    }
+    // Specially mark a named physical register as an "argument" so that it is
+    // considered live upon function entry.  Otherwise it's possible to get
+    // liveness validation errors for saving callee-save registers.
+    Func->addImplicitArg(Reg);
+    // Don't bother tracking the live range of a named physical register.
+    Reg->setIgnoreLiveness();
   }
   return Reg;
 }