[WebAssembly][AsmParser] Name missing features in error message

[tlively]

Summary

Rather than just saying that some feature is missing, report the exact
features to make the error message more useful and actionable.

[dschuff]

llvm/test/MC/WebAssembly/missing-features.s

7

might as well add one that requires more than one feature?

[tlively]

llvm/test/MC/WebAssembly/missing-features.s

7

I don't think we actually have any such instructions right now. But I'd rather keep the loop to be robust against adding any multi-feature instructions in the future.

[dschuff]

llvm/test/MC/WebAssembly/missing-features.s

7

hm, guess we missed our opportunity to define atomic SIMD loads :D

llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp

 #include "llvm/MC/MCSymbolWasm.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/TargetRegistry.h"
 
 using namespace llvm;
 
 #define DEBUG_TYPE "wasm-asm-parser"
 
+static const char *getSubtargetFeatureName(uint64_t Val);
+
 namespace {
 
 /// WebAssemblyOperand - Instances of this class represent the operands in a
 /// parsed Wasm machine instruction.
 struct WebAssemblyOperand : public MCParsedAsmOperand {
   enum KindTy { Token, Integer, Float, Symbol, BrList } Kind;
 
   SMLoc StartLoc, EndLoc;
#include "WebAssemblyGenAsmMatcher.inc"
   }
 
   bool MatchAndEmitInstruction(SMLoc IDLoc, unsigned & /*Opcode*/,
                                OperandVector &Operands, MCStreamer &Out,
                                uint64_t &ErrorInfo,
                                bool MatchingInlineAsm) override {
     MCInst Inst;
     Inst.setLoc(IDLoc);
-    unsigned MatchResult =
-        MatchInstructionImpl(Operands, Inst, ErrorInfo, MatchingInlineAsm);
+    FeatureBitset MissingFeatures;
+    unsigned MatchResult = MatchInstructionImpl(
+        Operands, Inst, ErrorInfo, MissingFeatures, MatchingInlineAsm);
     switch (MatchResult) {
     case Match_Success: {
       ensureLocals(Out);
       // Fix unknown p2align operands.
       auto Align = WebAssembly::GetDefaultP2AlignAny(Inst.getOpcode());
       if (Align != -1U) {
         auto &Op0 = Inst.getOperand(0);
         if (Op0.getImm() == -1)
case Match_Success: {
       Out.emitInstruction(Inst, getSTI());
       if (CurrentState == EndFunction) {
         onEndOfFunction();
       } else {
         CurrentState = Instructions;
       }
       return false;
     }
-    case Match_MissingFeature:
-      return Parser.Error(
-          IDLoc, "instruction requires a Wasm feature not currently enabled");
+    case Match_MissingFeature: {
+      auto NumMissing = MissingFeatures.count();
+      assert(NumMissing > 0 && "Expected missing features");
+      SmallString<128> Message;
+      raw_svector_ostream OS(Message);
+      OS << "instruction requires:";
+      for (unsigned i = 0, e = MissingFeatures.size(); i != e; ++i)
+        if (MissingFeatures.test(i))
+          OS << ' ' << getSubtargetFeatureName(i);
+      return Parser.Error(IDLoc, Message);
+    }
     case Match_MnemonicFail:
       return Parser.Error(IDLoc, "invalid instruction");
     case Match_NearMisses:
       return Parser.Error(IDLoc, "ambiguous instruction");
     case Match_InvalidTiedOperand:
     case Match_InvalidOperand: {
       SMLoc ErrorLoc = IDLoc;
       if (ErrorInfo != ~0ULL) {

 
 // Force static initialization.
 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyAsmParser() {
   RegisterMCAsmParser<WebAssemblyAsmParser> X(getTheWebAssemblyTarget32());
   RegisterMCAsmParser<WebAssemblyAsmParser> Y(getTheWebAssemblyTarget64());
 }
 
 #define GET_REGISTER_MATCHER
+#define GET_SUBTARGET_FEATURE_NAME
 #define GET_MATCHER_IMPLEMENTATION
 #include "WebAssemblyGenAsmMatcher.inc"

llvm/test/MC/WebAssembly/missing-features.s

+# RUN: not llvm-mc -triple=wasm32-unknown-unknown  < %s 2>&1 | FileCheck %s
+
+# Check that missing features are named in the error message
+
+# CHECK: error: instruction requires: simd128
+needs_simd:
+    .functype needs_simd () -> (v128)
+    i32.const 42
+    i32x4.splat
+    drop
+    end_function