Print single-bit bit range in more compact form

Author: s-barannikov

llvm/test/TableGen/DecoderEmitter/big-filter.td

@@ -14,12 +14,12 @@ class I : Instruction {
 // CHECK-LABEL: static const uint8_t DecoderTable128[32] = {
 // CHECK-NEXT:    OPC_SwitchField, 0, 64,      //  0: switch Inst[63:0] {
 // CHECK-NEXT:    1, 8,                        //  3: case 0x1: {
-// CHECK-NEXT:    OPC_CheckField, 127, 1, 1,   //  5:  check Inst[127:127] == 0x1
+// CHECK-NEXT:    OPC_CheckField, 127, 1, 1,   //  5:  check Inst[127] == 0x1
 // CHECK-NEXT:    OPC_Decode, {{[0-9, ]+}}, 0, //  9:  decode to I2 using decoder 0
 // CHECK-NEXT:                                 //  9: }
 // CHECK-NEXT:    255, 255, 255, 255, 255, 255, 255, 255, 255, 1, 0,
 // CHECK-NEXT:                                 // 13: case 0xffffffffffffffff: {
-// CHECK-NEXT:    OPC_CheckField, 127, 1, 0,   // 24:  check Inst[127:127] == 0x0
+// CHECK-NEXT:    OPC_CheckField, 127, 1, 0,   // 24:  check Inst[127] == 0x0
 // CHECK-NEXT:    OPC_Decode, {{[0-9, ]+}}, 0, // 28:  decode to I1 using decoder 0
 // CHECK-NEXT:                                 // 28: }
 // CHECK-NEXT:                                 // 28: } // switch Inst[63:0]

llvm/test/TableGen/DecoderEmitter/trydecode-emission2.td

@@ -31,7 +31,7 @@ def InstB : TestInstruction {
 }
 
 // CHECK-LABEL: static const uint8_t DecoderTable8[26] = {
-// CHECK-NEXT:    OPC_CheckField, 2, 1, 0,     //  0: check Inst[2:2] == 0x0
+// CHECK-NEXT:    OPC_CheckField, 2, 1, 0,     //  0: check Inst[2] == 0x0
 // CHECK-NEXT:    OPC_CheckField, 5, 3, 0,     //  4: check Inst[7:5] == 0x0
 // CHECK-NEXT:    OPC_Scope, 8,                //  8: try {
 // CHECK-NEXT:    OPC_CheckField, 0, 2, 3,     // 10:  check Inst[1:0] == 0x3

llvm/test/TableGen/DecoderEmitter/var-len-conflict-1.td

@@ -18,7 +18,7 @@ class I : Instruction {
 // 00000001 ________  I16_1
 // 00000010 ________  I16_2
 
-// CHECK: switch Inst[0:0]
+// CHECK: switch Inst[0]
 // CHECK: decode to I8_0
 // CHECK: decode to I8_1
 // CHECK: switch Inst[15:8]

llvm/utils/TableGen/DecoderTableEmitter.cpp

@@ -160,7 +160,7 @@ void DecoderTableEmitter::emitULEB128(uint64_t Val) {
   emitByte(Val);
 }
 
-formatted_raw_ostream &DecoderTableEmitter::emitComment(indent Indent) {
+raw_ostream &DecoderTableEmitter::emitComment(indent Indent) {
   constexpr unsigned CommentColumn = 45;
   if (OS.getColumn() > CommentColumn)
     OS << '\n';
@@ -169,6 +169,23 @@ formatted_raw_ostream &DecoderTableEmitter::emitComment(indent Indent) {
   return OS;
 }
 
+namespace {
+
+/// Helper class for printing bit ranges.
+struct BitRange {
+  unsigned MSB, LSB;
+
+  friend raw_ostream &operator<<(raw_ostream &OS, BitRange R) {
+    if (R.MSB == R.LSB)
+      OS << '[' << R.LSB << ']';
+    else
+      OS << '[' << R.MSB << ':' << R.LSB << ']';
+    return OS;
+  }
+};
+
+} // namespace
+
 void DecoderTableEmitter::emitCheckAnyNode(const CheckAnyNode *N,
                                            indent Indent) {
   // TODO: Single-child CheckAny node should be optimized out. For now,
@@ -210,7 +227,7 @@ void DecoderTableEmitter::emitSwitchFieldNode(const SwitchFieldNode *N,
   emitULEB128(LSB);
   emitUInt8(Width);
 
-  emitComment(Indent) << "switch Inst[" << MSB << ':' << LSB << "] {\n";
+  emitComment(Indent) << "switch Inst" << BitRange{MSB, LSB} << " {\n";
 
   for (auto [Val, Child] : drop_end(N->cases())) {
     emitStartLine();
@@ -231,7 +248,7 @@ void DecoderTableEmitter::emitSwitchFieldNode(const SwitchFieldNode *N,
   emitNode(Child, Indent + 1);
   emitComment(Indent) << "}\n";
 
-  emitComment(Indent) << "} // switch Inst[" << MSB << ':' << LSB << "]\n";
+  emitComment(Indent) << "} // switch Inst" << BitRange{MSB, LSB} << "\n";
 }
 
 void DecoderTableEmitter::emitCheckFieldNode(const CheckFieldNode *N,
@@ -246,9 +263,8 @@ void DecoderTableEmitter::emitCheckFieldNode(const CheckFieldNode *N,
   emitUInt8(Width);
   emitULEB128(Val);
 
-  emitComment(Indent);
-  OS << "check Inst[" << MSB << ':' << LSB << "] == " << format_hex(Val, 0)
-     << '\n';
+  emitComment(Indent) << "check Inst" << BitRange{MSB, LSB}
+                      << " == " << format_hex(Val, 0) << '\n';
 }
 
 void DecoderTableEmitter::emitCheckPredicateNode(const CheckPredicateNode *N,

llvm/utils/TableGen/DecoderTableEmitter.h

@@ -72,7 +72,7 @@ class DecoderTableEmitter {
   void emitByte(uint8_t Val);
   void emitUInt8(unsigned Val);
   void emitULEB128(uint64_t Val);
-  formatted_raw_ostream &emitComment(indent Indent);
+  raw_ostream &emitComment(indent Indent);
 
   void emitCheckAnyNode(const CheckAnyNode *N, indent Indent);
   void emitCheckAllNode(const CheckAllNode *N, indent Indent);