[llvm] r322936 - [CodeGen] Unify printing format of debug-location in both MIR and -debug

[Vedant Kumar via llvm-commits]

Hi Francis,

I'm debugging an issue in selection-dag which results in strange stepping behavior for swift code (rdar://33755881 <rdar://33755881>).

Before this patch, the output of -print-after-all would show this:

	MOV16mr %rbp, 1, %noreg, -112, %noreg, killed renamable %ax; mem:ST2[%92] dbg:stepping.swift:8:17
	renamable %edx = MOVZX32rm16 %rbp, 1, %noreg, -112, %noreg; mem:LD2[%93](dereferenceable) dbg:stepping.swift:10:17

It's clear to see where the bug is based on this output, because we'd step from line 8 to line 10 and skip line 9.

After this patch, it's harder to identify the issue:

  MOV16mr $rbp, 1, $noreg, -112, $noreg, killed renamable $ax, debug-location !56 :: (store 2 into %ir.._value12)
  renamable $edx = MOVZX32rm16 $rbp, 1, $noreg, -112, $noreg, debug-location !62 :: (dereferenceable load 2 from %ir.._value13)

The problem is that it's not immediately clear that locations 56 and 62 are on different lines.

Would you be open to bringing the old kind of output back (possibly under a flag)?

vedant

> On Jan 19, 2018, at 3:44 AM, Francis Visoiu Mistrih via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
> Author: thegameg
> Date: Fri Jan 19 03:44:42 2018
> New Revision: 322936
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=322936&view=rev
> Log:
> [CodeGen] Unify printing format of debug-location in both MIR and -debug
> 
> Use "debug-location" instead of "; dbg:" in MI::print.
> 
> Modified:
>    llvm/trunk/lib/CodeGen/MIRPrinter.cpp
>    llvm/trunk/lib/CodeGen/MachineInstr.cpp
>    llvm/trunk/unittests/CodeGen/MachineInstrTest.cpp
> 
> Modified: llvm/trunk/lib/CodeGen/MIRPrinter.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MIRPrinter.cpp?rev=322936&r1=322935&r2=322936&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/MIRPrinter.cpp (original)
> +++ llvm/trunk/lib/CodeGen/MIRPrinter.cpp Fri Jan 19 03:44:42 2018
> @@ -686,11 +686,11 @@ void MIPrinter::print(const MachineInstr
>     NeedComma = true;
>   }
> 
> -  if (MI.getDebugLoc()) {
> +  if (const DebugLoc &DL = MI.getDebugLoc()) {
>     if (NeedComma)
>       OS << ',';
>     OS << " debug-location ";
> -    MI.getDebugLoc()->printAsOperand(OS, MST);
> +    DL->printAsOperand(OS, MST);
>   }
> 
>   if (!MI.memoperands_empty()) {
> 
> Modified: llvm/trunk/lib/CodeGen/MachineInstr.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineInstr.cpp?rev=322936&r1=322935&r2=322936&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/MachineInstr.cpp (original)
> +++ llvm/trunk/lib/CodeGen/MachineInstr.cpp Fri Jan 19 03:44:42 2018
> @@ -1425,6 +1425,15 @@ void MachineInstr::print(raw_ostream &OS
>     }
>   }
> 
> +  if (!SkipDebugLoc) {
> +    if (const DebugLoc &DL = getDebugLoc()) {
> +      if (!FirstOp)
> +        OS << ',';
> +      OS << " debug-location ";
> +      DL->printAsOperand(OS, MST);
> +    }
> +  }
> +
>   bool HaveSemi = false;
>   if (!memoperands_empty()) {
>     if (!HaveSemi) {
> @@ -1441,6 +1450,9 @@ void MachineInstr::print(raw_ostream &OS
>     }
>   }
> 
> +  if (SkipDebugLoc)
> +    return;
> +
>   // Print debug location information.
>   if (isDebugValue() && getOperand(e - 2).isMetadata()) {
>     if (!HaveSemi)
> @@ -1457,13 +1469,6 @@ void MachineInstr::print(raw_ostream &OS
>     }
>     if (isIndirectDebugValue())
>       OS << " indirect";
> -  } else if (SkipDebugLoc) {
> -    return;
> -  } else if (debugLoc && MF) {
> -    if (!HaveSemi)
> -      OS << ";";
> -    OS << " dbg:";
> -    debugLoc.print(OS);
>   }
> 
>   OS << '\n';
> 
> Modified: llvm/trunk/unittests/CodeGen/MachineInstrTest.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/CodeGen/MachineInstrTest.cpp?rev=322936&r1=322935&r2=322936&view=diff
> ==============================================================================
> --- llvm/trunk/unittests/CodeGen/MachineInstrTest.cpp (original)
> +++ llvm/trunk/unittests/CodeGen/MachineInstrTest.cpp Fri Jan 19 03:44:42 2018
> @@ -14,6 +14,8 @@
> #include "llvm/CodeGen/TargetInstrInfo.h"
> #include "llvm/CodeGen/TargetLowering.h"
> #include "llvm/CodeGen/TargetSubtargetInfo.h"
> +#include "llvm/IR/DebugInfoMetadata.h"
> +#include "llvm/IR/ModuleSlotTracker.h"
> #include "llvm/Support/TargetRegistry.h"
> #include "llvm/Support/TargetSelect.h"
> #include "llvm/Target/TargetMachine.h"
> @@ -244,4 +246,25 @@ TEST(MachineInstrExpressionTraitTest, Is
> 
>   checkHashAndIsEqualMatch(VD2PU, VD2PD);
> }
> +
> +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);
> +  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 "));
> +}
> +
> } // end namespace
> 
> 
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