[llvm] [NFC][DecoderEmitter] Predicate generation code cleanup (PR #158140)

[Sergei Barannikov via llvm-commits]

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@@ -1266,15 +1238,15 @@ unsigned DecoderTableBuilder::getPredicateIndex(StringRef Predicate) const {
 }
 
 void DecoderTableBuilder::emitPredicateTableEntry(unsigned EncodingID) const {
-  if (!doesOpcodeNeedPredicate(EncodingID))
-    return;
-
   // Build up the predicate string.
   SmallString<256> Predicate;
-  // FIXME: emitPredicateMatch() functions can take a buffer directly rather
-  // than a stream.
   raw_svector_ostream PS(Predicate);
   emitPredicateMatch(PS, EncodingID);
+  // Predicate being empty indicates that there are no predicates.
+  // Predicate being "false" indicate that there are predicates but with no
+  // AssemblerMatcherPredicate.
+  if (Predicate.empty() || Predicate == "false")
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s-barannikov wrote:

It is unfortunate we have to check for "false" here. Maybe make emitPredicateMatch return true if it found any AssemblerPredicates? I think it could be useful in other places where this method is called.

https://github.com/llvm/llvm-project/pull/158140