[SlotIndexes] Add print-slotindexes to disable printing slotindexes

[jsji]

Summary

When we print the IR with --print-after/before-*,
SlotIndexes will be printed whenever available (We haven't freed it).

This introduces some noises when we try to compare the IR
among different optimizations.

eg:
-print-before=machine-cp will print SlotIndexes for 1st machine-cp
pass, but NOT for 2nd machine-cp;
-print-after=machine-cp will NOT print SlotIndexes for both
machine-cp passes.
So SlotIndexes in 1st pass introduce noises when differing these IRs.

This patch introduces an option to hide indexes.

[thegameg]

Can we also get a test for this?

llvm/lib/CodeGen/MachineBasicBlock.cpp

46

I'd rather have this init to true, and allow users to disable it when they want to get rid of it.

[jsji]

Keep the default behavior, add option to disable.
Also add a testcase.

[thegameg]

LGTM, thanks!

llvm/lib/CodeGen/MachineBasicBlock.cpp

 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
 #include <algorithm>
 using namespace llvm;
 
 #define DEBUG_TYPE "codegen"
 
+static cl::opt<bool> PrintSlotIndexes(
+    "print-slotindexes",
+    cl::desc("When printing machine IR, annotate instructions and blocks with "
+             "SlotIndexes when available"),
+    cl::init(true), cl::Hidden);
+
 MachineBasicBlock::MachineBasicBlock(MachineFunction &MF, const BasicBlock *B)
     : BB(B), Number(-1), xParent(&MF) {
   Insts.Parent = this;
   if (B)
     IrrLoopHeaderWeight = B->getIrrLoopHeaderWeight();
 }
 
 MachineBasicBlock::~MachineBasicBlock() {
void MachineBasicBlock::print(raw_ostream &OS, ModuleSlotTracker &MST,
                               bool IsStandalone) const {
   const MachineFunction *MF = getParent();
   if (!MF) {
     OS << "Can't print out MachineBasicBlock because parent MachineFunction"
        << " is null\n";
     return;
   }
 
-  if (Indexes)
+  if (Indexes && PrintSlotIndexes)
     OS << Indexes->getMBBStartIdx(this) << '\t';
 
   OS << "bb." << getNumber();
   bool HasAttributes = false;
   if (const auto *BB = getBasicBlock()) {
     if (BB->hasName()) {
       OS << "." << BB->getName();
     } else {
if (!livein_empty() && MRI.tracksLiveness()) {
     HasLineAttributes = true;
   }
 
   if (HasLineAttributes)
     OS << '\n';
 
   bool IsInBundle = false;
   for (const MachineInstr &MI : instrs()) {
-    if (Indexes) {
+    if (Indexes && PrintSlotIndexes) {
       if (Indexes->hasIndex(MI))
         OS << Indexes->getInstructionIndex(MI);
       OS << '\t';
     }
 
     if (IsInBundle && !MI.isInsideBundle()) {
       OS.indent(2) << "}\n";
       IsInBundle = false;

llvm/test/Other/print-slotindexes.ll

+; RUN: llc -print-after=slotindexes < %s 2>&1 | FileCheck %s --check-prefixes=ALL,SI 
+; RUN: llc -print-after=slotindexes -print-slotindexes=false < %s 2>&1 | FileCheck %s --check-prefixes=ALL,NOSI
+; REQUIRES: default_triple
+define void @foo(){
+  ret void
+}
+
+;CHECK: IR Dump {{.*}}
+;CHECK: # Machine code for function foo{{.*}}
+;SI: {{[0-9]+}}B bb.0 (%ir-block.0)
+;NOSI: {{^}}bb.0 (%ir-block.0)
+