[Asm] Improve "too few operands" errors

[olista01]

Summary

• We can still emit this error if the actual instruction has two or more operands missing compared to the expected one.
• We should only emit this error once per instruction.

[olista01]

Ping

[rengolin]

LGTM, thanks!

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

ARMAsmParser::FilterNearMisses(SmallVectorImpl<NearMissInfo> &NearMissesIn,
   // TODO: This is not all ARM-specific, can some of it be factored out?
 
   // Record some information about near-misses that we have already seen, so
   // that we can avoid reporting redundant ones. For example, if there are
   // variants of an instruction that take 8- and 16-bit immediates, we want
   // to only report the widest one.
   std::multimap<unsigned, unsigned> OperandMissesSeen;
   SmallSet<uint64_t, 4> FeatureMissesSeen;
+  bool ReportedTooFewOperands = false;
 
   // Process the near-misses in reverse order, so that we see more general ones
   // first, and so can avoid emitting more specific ones.
   for (NearMissInfo &I : reverse(NearMissesIn)) {
     switch (I.getKind()) {
     case NearMissInfo::NearMissOperand: {
       SMLoc OperandLoc =
           ((ARMOperand &)*Operands[I.getOperandIndex()]).getStartLoc();
case NearMissInfo::NearMissPredicate: {
       default:
         llvm_unreachable("Unhandled target predicate error");
         break;
       }
       NearMissesOut.emplace_back(Message);
       break;
     }
     case NearMissInfo::NearMissTooFewOperands: {
+      if (!ReportedTooFewOperands) {
         SMLoc EndLoc = ((ARMOperand &)*Operands.back()).getEndLoc();
-      NearMissesOut.emplace_back(
-          NearMissMessage{ EndLoc, StringRef("too few operands for instruction") });
+        NearMissesOut.emplace_back(NearMissMessage{
+            EndLoc, StringRef("too few operands for instruction")});
+        ReportedTooFewOperands = true;
+      }
       break;
     }
     case NearMissInfo::NoNearMiss:
       // This should never leave the matcher.
       llvm_unreachable("not a near-miss");
       break;
     }
   }

test/MC/ARM/diagnostics.s

 @ CHECK-ERRORS: error: immediate operand must a number in the range [0, 255]
 @ CHECK-ERRORS: error: immediate operand must an even number in the range [0, 30]
 @ CHECK-ERRORS: error: immediate operand must a number in the range [0, 255]
 @ CHECK-ERRORS: error: immediate operand must an even number in the range [0, 30]
 @ CHECK-ERRORS: error: immediate operand must a number in the range [0, 255]
 @ CHECK-ERRORS: error: immediate operand must an even number in the range [0, 30]
 @ CHECK-ERRORS: error: immediate operand must a number in the range [0, 255]
 @ CHECK-ERRORS: error: immediate operand must an even number in the range [0, 30]
+
+        @ Generic error for too few operands
+        adds
+        adds r0
+@ CHECK-ERRORS: error: too few operands for instruction
+@ CHECK-ERRORS: error: too few operands for instruction

test/MC/ARM/ldrd-strd-gnu-bad-inst.s

 @ RUN: not llvm-mc -triple=armv7-linux-gnueabi %s 2>&1 | FileCheck %s
 
   .text
   .thumb
-@ CHECK: error: invalid instruction
+@ CHECK: error: too few operands for instruction
   strd
-@ CHECK: error: invalid instruction
+@ CHECK: error: too few operands for instruction
   ldrd
-@ CHECK: error: invalid instruction
+@ CHECK: error: too few operands for instruction
   strd r0
-@ CHECK: error: invalid instruction
+@ CHECK: error: too few operands for instruction
   ldrd r0
 @ CHECK: error: invalid instruction
   strd s0, [r0]
 @ CHECK: error: invalid instruction
   ldrd s0, [r0]
   .arm
-@ CHECK: error: invalid instruction
+@ CHECK: error: too few operands for instruction
   strd
-@ CHECK: error: invalid instruction
+@ CHECK: error: too few operands for instruction
   ldrd
-@ CHECK: error: invalid instruction
+@ CHECK: error: too few operands for instruction
   strd r0
-@ CHECK: error: invalid instruction
+@ CHECK: error: too few operands for instruction
   ldrd r0
 @ CHECK: error: invalid instruction
   strd s0, [r0]
 @ CHECK: error: invalid instruction
   ldrd s0, [r0]

test/MC/ARM/thumb-diagnostics.s

@------------------------------------------------------------------------------
         stc2 p0, c8, [r1, #4]
         stc2l p6, c2, [r7, #4]
         ldc2 p0, c8, [r1, #4]
         ldc2l p6, c2, [r7, #4]
 @ CHECK-ERRORS: error: invalid instruction
 @ CHECK-ERRORS: error: invalid instruction
 @ CHECK-ERRORS: error: invalid instruction
 @ CHECK-ERRORS: error: invalid instruction
+
+@------------------------------------------------------------------------------
+@ Generic error for too few operands
+@------------------------------------------------------------------------------
+
+        adds
+        adds r0
+@ CHECK-ERRORS: error: too few operands for instruction
+@ CHECK-ERRORS: error: too few operands for instruction

test/MC/ARM/thumb2-diagnostics.s

@ CHECK-ERRORS: note: invalid operand for instruction
 
         @ SWP(B) is an ARM-only instruction
         swp  r0, r1, [r2]
         swpb r3, r4, [r5]
 @ CHECK-ERRORS-V7: error: instruction requires: arm-mode
 @ CHECK-ERRORS-V7: error: instruction requires: arm-mode
 @ CHECK-ERRORS-V8: error: invalid instruction
 @ CHECK-ERRORS-V8: error: invalid instruction
+
+        @ Generic error for too few operands
+        adds
+        adds r0
+@ CHECK-ERRORS: error: too few operands for instruction
+@ CHECK-ERRORS: error: too few operands for instruction

utils/TableGen/AsmMatcherEmitter.cpp

if (ReportMultipleNearMisses) {
     OS << "        bool ThisOperandValid = (Formal == " <<"InvalidMatchClass) || "
                                    "isSubclass(Formal, OptionalMatchClass);\n";
     OS << "        if (!ThisOperandValid) {\n";
     OS << "          if (!OperandNearMiss) {\n";
     OS << "            // Record info about match failure for later use.\n";
     OS << "            DEBUG_WITH_TYPE(\"asm-matcher\", dbgs() << \"recording too-few-operands near miss\\n\");\n";
     OS << "            OperandNearMiss =\n";
     OS << "                NearMissInfo::getTooFewOperands(Formal, it->Opcode);\n";
-    OS << "          } else {\n";
+    OS << "          } else if (OperandNearMiss.getKind() != NearMissInfo::NearMissTooFewOperands) {\n";
     OS << "            // If more than one operand is invalid, give up on this match entry.\n";
     OS << "            DEBUG_WITH_TYPE(\n";
     OS << "                \"asm-matcher\",\n";
     OS << "                dbgs() << \"second invalid operand, giving up on this opcode\\n\");\n";
     OS << "            MultipleInvalidOperands = true;\n";
     OS << "            break;\n";
     OS << "          }\n";
     OS << "        } else {\n";