[TableGen][GlobalISel] Refactor optimizeRules related bit to allow co…

…de reuse

In theory, reapplying optimizeRules on each group matchers should give
us a second nesting level on the matching table. In practice, we need
more work to make that happen because all the predicates are actually
not directly available through the predicate matchers list.

NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321025 91177308-0d34-0410-b5e6-96231b3b80d8

utils/TableGen/GlobalISelEmitter.cpp

@@ -574,6 +574,7 @@ class Matcher {
 public:
   virtual ~Matcher() = default;
   virtual void emit(MatchTable &Table) = 0;
+  virtual std::unique_ptr<PredicateMatcher> forgetFirstCondition() = 0;
 };
 
 class GroupMatcher : public Matcher {
@@ -595,6 +596,15 @@ class GroupMatcher : public Matcher {
     Rules.clear();
   }
   void emit(MatchTable &Table) override;
+
+  std::unique_ptr<PredicateMatcher> forgetFirstCondition() override {
+    // We shouldn't need to mess up with groups, since we
+    // should have merged everything shareable upfront.
+    // If we start to look into reordering predicates,
+    // we may want to reconsider this.
+    assert(0 && "Groups should be formed maximal for now");
+    llvm_unreachable("No need for this for now");
+  }
 };
 
 /// Generates code to check that a match rule matches.
@@ -749,7 +759,7 @@ class RuleMatcher : public Matcher {
   /// matcher.
   unsigned countRendererFns() const;
 
-  std::unique_ptr<PredicateMatcher> forgetFirstCondition();
+  std::unique_ptr<PredicateMatcher> forgetFirstCondition() override;
 
   // FIXME: Remove this as soon as possible
   InstructionMatcher &insnmatchers_front() const { return *Matchers.front(); }
@@ -2615,7 +2625,7 @@ class GlobalISelEmitter {
   ///   # predicate C
   /// \endverbatim
   std::vector<Matcher *> optimizeRules(
-      std::vector<RuleMatcher> &Rules,
+      const std::vector<Matcher *> &Rules,
       std::vector<std::unique_ptr<GroupMatcher>> &StorageGroupMatcher);
 };
 
@@ -3552,15 +3562,15 @@ void GlobalISelEmitter::emitImmPredicates(
 }
 
 std::vector<Matcher *> GlobalISelEmitter::optimizeRules(
-    std::vector<RuleMatcher> &Rules,
+    const std::vector<Matcher *> &Rules,
     std::vector<std::unique_ptr<GroupMatcher>> &StorageGroupMatcher) {
   std::vector<Matcher *> OptRules;
   // Start with a stupid grouping for now.
   std::unique_ptr<GroupMatcher> CurrentGroup = make_unique<GroupMatcher>();
   assert(CurrentGroup->conditions_empty());
   unsigned NbGroup = 0;
-  for (RuleMatcher &Rule : Rules) {
-    std::unique_ptr<PredicateMatcher> Predicate = Rule.forgetFirstCondition();
+  for (Matcher *Rule : Rules) {
+    std::unique_ptr<PredicateMatcher> Predicate = Rule->forgetFirstCondition();
     if (!CurrentGroup->conditions_empty() &&
         !CurrentGroup->lastConditionMatches(*Predicate)) {
       // Start a new group.
@@ -3572,7 +3582,7 @@ std::vector<Matcher *> GlobalISelEmitter::optimizeRules(
     }
     if (CurrentGroup->conditions_empty())
       CurrentGroup->addCondition(std::move(Predicate));
-    CurrentGroup->addRule(Rule);
+    CurrentGroup->addRule(*Rule);
   }
   if (!CurrentGroup->conditions_empty()) {
     ++NbGroup;
@@ -3823,12 +3833,13 @@ void GlobalISelEmitter::run(raw_ostream &OS) {
   });
   std::vector<std::unique_ptr<GroupMatcher>> StorageGroupMatcher;
 
-  std::vector<Matcher *> OptRules;
-  if (OptimizeMatchTable)
-    OptRules = optimizeRules(Rules, StorageGroupMatcher);
-  else
-    for (Matcher &Rule : Rules)
-      OptRules.push_back(&Rule);
+  std::vector<Matcher *> InputRules;
+  for (Matcher &Rule : Rules)
+    InputRules.push_back(&Rule);
+
+  std::vector<Matcher *> OptRules =
+      OptimizeMatchTable ? optimizeRules(InputRules, StorageGroupMatcher)
+                         : InputRules;
 
   MatchTable Table(0);
   for (Matcher *Rule : OptRules) {