[TableGen] Remove predicate filtering from GenerateVariants.

[craig.topper]

Summary

After D100691, predicates should be cheap to compare again so
we don't need to filter anymore.

This is mostly just a revert of several patches going back to 2018.

[craig.topper]

Add the HwModeFeatures comparison I accidentally removed.

[craig.topper]

Remove the HwModeFeature check. We're running this before HwMode expansion. Just assert that the string is empty.

[kparzysz]

Looks ok to me, but waiting for the prerequisite patch to be finalized.

[craig.topper]

Rebase

llvm/utils/TableGen/CodeGenDAGPatterns.cpp

 //===- CodeGenDAGPatterns.cpp - Read DAG patterns from .td file -----------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the CodeGenDAGPatterns class, which is used to read and
 // represent the patterns present in a .td file for instructions.
 //
 //===----------------------------------------------------------------------===//
 
 #include "CodeGenDAGPatterns.h"
-#include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/Twine.h"
void CodeGenDAGPatterns::GenerateVariants() {
   // generate variants of the instruction, through the exploitation of
   // identities.  This permits the target to provide aggressive matching without
   // the .td file having to contain tons of variants of instructions.
   //
   // Note that this loop adds new patterns to the PatternsToMatch list, but we
   // intentionally do not reconsider these.  Any variants of added patterns have
   // already been added.
   //
-  const unsigned NumOriginalPatterns = PatternsToMatch.size();
-  BitVector MatchedPatterns(NumOriginalPatterns);
-  std::vector<BitVector> MatchedPredicates(NumOriginalPatterns,
-                                           BitVector(NumOriginalPatterns));
-
-  typedef std::pair<MultipleUseVarSet, std::vector<TreePatternNodePtr>>
-      DepsAndVariants;
-  std::map<unsigned, DepsAndVariants> PatternsWithVariants;
-
-  // Collect patterns with more than one variant.
-  for (unsigned i = 0; i != NumOriginalPatterns; ++i) {
+  for (unsigned i = 0, e = PatternsToMatch.size(); i != e; ++i) {
     MultipleUseVarSet DepVars;
     std::vector<TreePatternNodePtr> Variants;
     FindDepVars(PatternsToMatch[i].getSrcPattern(), DepVars);
     LLVM_DEBUG(errs() << "Dependent/multiply used variables: ");
     LLVM_DEBUG(DumpDepVars(DepVars));
     LLVM_DEBUG(errs() << "\n");
     GenerateVariantsOf(PatternsToMatch[i].getSrcPatternShared(), Variants,
                        *this, DepVars);
 
+    assert(PatternsToMatch[i].getHwModeFeatures().empty() &&
+           "HwModes should not have been expanded yet!");
+
     assert(!Variants.empty() && "Must create at least original variant!");
     if (Variants.size() == 1) // No additional variants for this pattern.
       continue;
 
     LLVM_DEBUG(errs() << "FOUND VARIANTS OF: ";
                PatternsToMatch[i].getSrcPattern()->dump(); errs() << "\n");
 
-    PatternsWithVariants[i] = std::make_pair(DepVars, Variants);
-
-    // Cache matching predicates.
-    if (MatchedPatterns[i])
-      continue;
-
-    ListInit *Predicates = PatternsToMatch[i].getPredicates();
-    const std::string &HwModeFeatures = PatternsToMatch[i].getHwModeFeatures();
-
-    BitVector &Matches = MatchedPredicates[i];
-    MatchedPatterns.set(i);
-    Matches.set(i);
-
-    // Don't test patterns that have already been cached - it won't match.
-    for (unsigned p = 0; p != NumOriginalPatterns; ++p)
-      if (!MatchedPatterns[p])
-        Matches[p] = (Predicates == PatternsToMatch[p].getPredicates()) &&
-                     (HwModeFeatures == PatternsToMatch[p].getHwModeFeatures());
-
-    // Copy this to all the matching patterns.
-    for (int p = Matches.find_first(); p != -1; p = Matches.find_next(p))
-      if (p != (int)i) {
-        MatchedPatterns.set(p);
-        MatchedPredicates[p] = Matches;
-      }
-  }
-
-  for (const auto &it : PatternsWithVariants) {
-    unsigned i = it.first;
-    const MultipleUseVarSet &DepVars = it.second.first;
-    const std::vector<TreePatternNodePtr> &Variants = it.second.second;
-
     for (unsigned v = 0, e = Variants.size(); v != e; ++v) {
       TreePatternNodePtr Variant = Variants[v];
-      BitVector &Matches = MatchedPredicates[i];
 
       LLVM_DEBUG(errs() << "  VAR#" << v << ": "; Variant->dump();
                  errs() << "\n");
 
       // Scan to see if an instruction or explicit pattern already matches this.
       bool AlreadyExists = false;
       for (unsigned p = 0, e = PatternsToMatch.size(); p != e; ++p) {
         // Skip if the top level predicates do not match.
-        if (!Matches[p])
+        if ((i != p) && (PatternsToMatch[i].getPredicates() !=
+                         PatternsToMatch[p].getPredicates()))
           continue;
         // Check to see if this variant already exists.
         if (Variant->isIsomorphicTo(PatternsToMatch[p].getSrcPattern(),
                                     DepVars)) {
           LLVM_DEBUG(errs() << "  *** ALREADY EXISTS, ignoring variant.\n");
           AlreadyExists = true;
           break;
         }
       }
       // If we already have it, ignore the variant.
       if (AlreadyExists) continue;
 
       // Otherwise, add it to the list of patterns we have.
       PatternsToMatch.emplace_back(
           PatternsToMatch[i].getSrcRecord(), PatternsToMatch[i].getPredicates(),
           Variant, PatternsToMatch[i].getDstPatternShared(),
           PatternsToMatch[i].getDstRegs(),
           PatternsToMatch[i].getAddedComplexity(), Record::getNewUID(),
           PatternsToMatch[i].getForceMode(),
           PatternsToMatch[i].getHwModeFeatures());
-      MatchedPredicates.push_back(Matches);
-
-      // Add a new match the same as this pattern.
-      for (auto &P : MatchedPredicates)
-        P.push_back(P[i]);
     }
 
     LLVM_DEBUG(errs() << "\n");
   }
 }