[CodeGen] Print user-friendly debug locations as MI comments

[thegameg]

Summary

If available, print the file, line and column of the DebugLoc attached to the MachineInstr:

MOV16mr $rbp, 1, $noreg, -112, $noreg, killed renamable $ax, debug-location !56 :: (store 2 into %ir.._value12); stepping.swift:10:17

renamable $edx = MOVZX32rm16 $rbp, 1, $noreg, -112, $noreg, debug-location !62 :: (dereferenceable load 2 from %ir.._value13); stepping.swift:10:17

[vsk]

Thanks, lgtm!

[JDevlieghere]

Thanks Francis, LGTM!

lib/CodeGen/MachineInstr.cpp

for (const MachineMemOperand *Op : memoperands()) {
       NeedComma = true;
     }
   }
 
   if (SkipDebugLoc)
     return;
 
   bool HaveSemi = false;
+
   // Print debug location information.
+  if (const DebugLoc &DL = getDebugLoc()) {
+    if (!HaveSemi) {
+      OS << ';';
+      HaveSemi = true;
+    }
+    OS << ' ';
+    DL.print(OS);
+  }
+
+  // Print extra comments for DEBUG_VALUE.
   if (isDebugValue() && getOperand(e - 2).isMetadata()) {
-    if (!HaveSemi)
+    if (!HaveSemi) {
       OS << ";";
+      HaveSemi = true;
+    }
     auto *DV = cast<DILocalVariable>(getOperand(e - 2).getMetadata());
     OS << " line no:" <<  DV->getLine();
     if (auto *InlinedAt = debugLoc->getInlinedAt()) {
       DebugLoc InlinedAtDL(InlinedAt);
       if (InlinedAtDL && MF) {
         OS << " inlined @[ ";
         InlinedAtDL.print(OS);
         OS << " ]";

unittests/CodeGen/MachineInstrTest.cpp

 TEST(MachineInstrPrintingTest, DebugLocPrinting) {
   auto MF = createMachineFunction();
 
   MCOperandInfo OpInfo{0, 0, MCOI::OPERAND_REGISTER, 0};
   MCInstrDesc MCID = {0, 1,       1,       0,       0, 0,
                       0, nullptr, nullptr, &OpInfo, 0, nullptr};
 
   LLVMContext Ctx;
-  DILocation *DIL = DILocation::get(Ctx, 1, 5, (Metadata *)nullptr, nullptr);
+  DIFile *DIF = DIFile::getDistinct(Ctx, "filename", "");
+  DISubprogram *DIS = DISubprogram::getDistinct(
+      Ctx, nullptr, "", "", DIF, 0, nullptr, false, false, 0, nullptr, 0, 0, 0,
+      DINode::FlagZero, false, nullptr);
+  DILocation *DIL = DILocation::get(Ctx, 1, 5, DIS);
   DebugLoc DL(DIL);
   MachineInstr *MI = MF->CreateMachineInstr(MCID, DL);
   MI->addOperand(*MF, MachineOperand::CreateReg(0, /*isDef*/ true));
 
   std::string str;
   raw_string_ostream OS(str);
   MI->print(OS);
   ASSERT_TRUE(
       StringRef(OS.str()).startswith("$noreg = UNKNOWN debug-location "));
+  ASSERT_TRUE(
+      StringRef(OS.str()).endswith("filename:1:5"));
 }
 
 } // end namespace