[AsmPrinter] Add per BB instruction mix remark.

This patch adds a remarks that provides counts for each opcode per basic block.

An snippet of the generated information can be seen below.

The current implementation uses the target specific opcode for the counts. For example, on AArch64 this means we currently get 2 entries for `add` instructions if the block contains 32 and 64 bit adds. Similarly, immediate version are treated differently.

Unfortunately there seems to be no convenient way to get only the mnemonic part of the instruction as a string AFAIK. This could be improved in the future.

```
--- !Analysis
Pass:            asm-printer
Name:            InstructionMix
DebugLoc:        { File: arm64-instruction-mix-remarks.ll, Line: 30, Column: 30 }
Function:        foo
Args:
  - String:          'BasicBlock: '
  - BasicBlock:      else
  - String:          "\n"
  - String:          INST_MADDWrrr
  - String:          ': '
  - INST_MADDWrrr:   '2'
  - String:          "\n"
  - String:          INST_MOVZWi
  - String:          ': '
  - INST_MOVZWi:     '1'
```

Reviewed By: anemet, thegameg, paquette

Differential Revision: https://reviews.llvm.org/D89892

Author: fhahn

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -1134,9 +1134,12 @@ void AsmPrinter::emitFunctionBody() {
   bool HasAnyRealCode = false;
   int NumInstsInFunction = 0;
 
+  bool CanDoExtraAnalysis = ORE->allowExtraAnalysis(DEBUG_TYPE);
+  const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
   for (auto &MBB : *MF) {
     // Print a label for the basic block.
     emitBasicBlockStart(MBB);
+    DenseMap<unsigned, unsigned> OpcodeCounts;
     for (auto &MI : MBB) {
       // Print the assembly for the instruction.
       if (!MI.isPosition() && !MI.isImplicitDef() && !MI.isKill() &&
@@ -1202,6 +1205,10 @@ void AsmPrinter::emitFunctionBody() {
         break;
       default:
         emitInstruction(&MI);
+        if (CanDoExtraAnalysis) {
+          auto I = OpcodeCounts.insert({MI.getOpcode(), 0u});
+          I.first->second++;
+        }
         break;
       }
 
@@ -1245,6 +1252,35 @@ void AsmPrinter::emitFunctionBody() {
       }
     }
     emitBasicBlockEnd(MBB);
+
+    if (CanDoExtraAnalysis) {
+      // Skip empty blocks.
+      if (MBB.empty())
+        continue;
+
+      MachineOptimizationRemarkAnalysis R(DEBUG_TYPE, "InstructionMix",
+                                          MBB.begin()->getDebugLoc(), &MBB);
+
+      // Generate instruction mix remark. First, convert opcodes to string
+      // names, then sort them in descending order by count and name.
+      SmallVector<std::pair<std::string, unsigned>, 128> OpcodeCountsVec;
+      for (auto &KV : OpcodeCounts) {
+        auto Name = (Twine("INST_") + TII->getName(KV.first)).str();
+        OpcodeCountsVec.emplace_back(Name, KV.second);
+      }
+      sort(OpcodeCountsVec, [](const std::pair<std::string, unsigned> &A,
+                               const std::pair<std::string, unsigned> &B) {
+        if (A.second > B.second)
+          return true;
+        if (A.second == B.second)
+          return A.first < B.first;
+        return false;
+      });
+      R << "BasicBlock: " << ore::NV("BasicBlock", MBB.getName()) << "\n";
+      for (auto &KV : OpcodeCountsVec)
+        R << KV.first << ": " << ore::NV(KV.first, KV.second) << "\n";
+      ORE->emit(R);
+    }
   }
 
   EmittedInsts += NumInstsInFunction;

llvm/test/CodeGen/AArch64/arm64-instruction-mix-remarks.ll

@@ -0,0 +1,75 @@
+; RUN: llc -mtriple=arm64-apple-ios7.0 -pass-remarks-output=%t -pass-remarks=asm-printer -o - %s | FileCheck %s
+; RUN: FileCheck --input-file=%t --check-prefix=YAML %s
+
+; CHECK-LABEL: %entry
+; CHECK-NEXT:   ldr w8, [x0]
+; CHECK-NEXT:   add w8, w8, w1
+; CHECK-NEXT:   cmp w8, #100
+; CHECK-NEXT:   b.ne    LBB0_2
+
+; YAML:      Name:            InstructionMix
+; YAML-NEXT: DebugLoc:        { File: arm64-instruction-mix-remarks.ll, Line: 10, Column: 10 }
+; YAML-NEXT: Function:        foo
+; YAML-NEXT: Args:
+; YAML:      - BasicBlock:      entry
+; YAML:      - INST_ADDWrs:     '1'
+; YAML:      - INST_Bcc:        '1'
+; YAML:      - INST_LDRWui:     '1'
+; YAML:      - INST_SUBSWri:    '1'
+
+
+; CHECK-LABEL: %then
+; CHECK-NEXT:    mov w0, w8
+; CHECK-NEXT:    ret
+
+; YAML:      Name:            InstructionMix
+; YAML-NEXT: DebugLoc:        { File: arm64-instruction-mix-remarks.ll, Line: 20, Column: 20 }
+; YAML-NEXT: Function:        foo
+; YAML-NEXT: Args:
+; YAML:        - BasicBlock:      then
+; YAML:        - INST_ORRWrs:     '1'
+; YAML:        - INST_RET:        '1'
+
+; CHECK-LABEL: %else
+; CHECK-NEXT:    mul w8, w8, w1
+; CHECK-NEXT:    mov w9, #10
+; CHECK-NEXT:    mul w8, w8, w1
+; CHECK-NEXT:    str w9, [x0]
+; CHECK-NEXT:    mov w0, w8
+; CHECK-NEXT:    ret
+
+; YAML:      Name:            InstructionMix
+; YAML-NEXT: DebugLoc:        { File: arm64-instruction-mix-remarks.ll, Line: 30, Column: 30 }
+; YAML-NEXT: Function:        foo
+; YAML-NEXT: Args:
+; YAML:       - BasicBlock:      else
+; YAML:       - INST_MADDWrrr:   '2'
+; YAML:       - INST_ORRWrs:     '1'
+; YAML:       - INST_RET:        '1'
+; YAML:       - INST_STRWui:     '1'
+define i32 @foo(i32* %ptr, i32 %x) !dbg !3 {
+entry:
+  %l = load i32, i32* %ptr, !dbg !4
+  %add = add i32 %l, %x, !dbg !4
+  %c = icmp eq i32 %add, 100, !dbg !4
+  br i1 %c, label %then, label %else, !dbg !4
+
+then:
+  ret i32 %add, !dbg !5
+
+else:
+  store i32 10, i32* %ptr, !dbg !6
+  %res = mul i32 %add, %x, !dbg !6
+  %res.2 = mul i32 %res, %x, !dbg !6
+  ret i32 %res.2, !dbg !6
+}
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1)
+!1 = !DIFile(filename: "arm64-instruction-mix-remarks.ll", directory: "")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 5, scopeLine: 5, unit: !0)
+!4 = distinct !DILocation(line: 10, column: 10, scope: !3)
+!5 = distinct !DILocation(line: 20, column: 20, scope: !3)
+!6 = distinct !DILocation(line: 30, column: 30, scope: !3)