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

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

Differential Revision: https://reviews.llvm.org/D85795

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

@@ -35,6 +35,8 @@ 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
@@ -836,8 +838,9 @@ public:
                                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);
@@ -866,9 +869,17 @@ public:
       }
       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:
@@ -932,5 +943,6 @@ extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyAsmParser() {
 }
 
 #define GET_REGISTER_MATCHER
+#define GET_SUBTARGET_FEATURE_NAME
 #define GET_MATCHER_IMPLEMENTATION
 #include "WebAssemblyGenAsmMatcher.inc"

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

@@ -0,0 +1,11 @@
+# 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