[MachineVerifier] Include offending register in allocatable live-in error msg.

[fhahn]

Summary

This patch adds a convenience report() method for physical registers and
uses it to print the offending register with the 'MBB has allocatable
live-in' error.

[dsanders]

LGTM

llvm/trunk/lib/CodeGen/MachineVerifier.cpp

void report(const char *msg, const MachineOperand *MO, unsigned MONum,
                 LLT MOVRegType = LLT{});
 
     void report_context(const LiveInterval &LI) const;
     void report_context(const LiveRange &LR, unsigned VRegUnit,
                         LaneBitmask LaneMask) const;
     void report_context(const LiveRange::Segment &S) const;
     void report_context(const VNInfo &VNI) const;
     void report_context(SlotIndex Pos) const;
+    void report_context(MCPhysReg PhysReg) const;
     void report_context_liverange(const LiveRange &LR) const;
     void report_context_lanemask(LaneBitmask LaneMask) const;
     void report_context_vreg(unsigned VReg) const;
     void report_context_vreg_regunit(unsigned VRegOrUnit) const;
 
     void verifyInlineAsm(const MachineInstr *MI);
 
     void checkLiveness(const MachineOperand *MO, unsigned MONum);

 void MachineVerifier::report_context(const VNInfo &VNI) const {
   errs() << "- ValNo:       " << VNI.id << " (def " << VNI.def << ")\n";
 }
 
 void MachineVerifier::report_context_liverange(const LiveRange &LR) const {
   errs() << "- liverange:   " << LR << '\n';
 }
 
+void MachineVerifier::report_context(MCPhysReg PReg) const {
+  errs() << "- p. register: " << printReg(PReg, TRI) << '\n';
+}
+
 void MachineVerifier::report_context_vreg(unsigned VReg) const {
   errs() << "- v. register: " << printReg(VReg, TRI) << '\n';
 }
 
 void MachineVerifier::report_context_vreg_regunit(unsigned VRegOrUnit) const {
   if (TargetRegisterInfo::isVirtualRegister(VRegOrUnit)) {
     report_context_vreg(VRegOrUnit);
   } else {
MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
   if (!MF->getProperties().hasProperty(
       MachineFunctionProperties::Property::NoPHIs) && MRI->tracksLiveness()) {
     // If this block has allocatable physical registers live-in, check that
     // it is an entry block or landing pad.
     for (const auto &LI : MBB->liveins()) {
       if (isAllocatable(LI.PhysReg) && !MBB->isEHPad() &&
           MBB->getIterator() != MBB->getParent()->begin()) {
         report("MBB has allocatable live-in, but isn't entry or landing-pad.", MBB);
+        report_context(LI.PhysReg);
       }
     }
   }
 
   // Count the number of landing pad successors.
   SmallPtrSet<MachineBasicBlock*, 4> LandingPadSuccs;
   for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
        E = MBB->succ_end(); I != E; ++I) {