From bfe0f6957bccfcde83f323aec4d3a164bc0c3c7d Mon Sep 17 00:00:00 2001
From: Ahmed Bougacha <ahmed.bougacha@gmail.com>
Date: Thu, 27 Aug 2015 20:43:34 +0000
Subject: [PATCH] [TableGen][DAGISel] Dedup predicates with same code to run.
 NFCI.

I locally hit the 255 limit, but a lot of these are redundant: each
predicate coming from a different record was allocated a new number,
even when we already emitted the same code for another predicate.

Instead, re-use numbers and emit the predicate code only once.
This reduces the total text size of *DAGISel.cpp.o by ~1%.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246208 91177308-0d34-0410-b5e6-96231b3b80d8
---
 utils/TableGen/DAGISelMatcherEmitter.cpp | 29 ++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/utils/TableGen/DAGISelMatcherEmitter.cpp b/utils/TableGen/DAGISelMatcherEmitter.cpp
index fcae48d260b..26f53dca636 100644
--- a/utils/TableGen/DAGISelMatcherEmitter.cpp
+++ b/utils/TableGen/DAGISelMatcherEmitter.cpp
@@ -16,6 +16,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/TinyPtrVector.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FormattedStream.h"
 #include "llvm/TableGen/Record.h"
@@ -36,6 +37,10 @@ class MatcherTableEmitter {
   
   DenseMap<TreePattern *, unsigned> NodePredicateMap;
   std::vector<TreePredicateFn> NodePredicates;
+
+  // We de-duplicate the predicates by code string, and use this map to track
+  // all the patterns with "identical" predicates.
+  StringMap<TinyPtrVector<TreePattern *>> NodePredicatesByCodeToRun;
   
   StringMap<unsigned> PatternPredicateMap;
   std::vector<std::string> PatternPredicates;
@@ -62,10 +67,23 @@ private:
                        formatted_raw_ostream &OS);
 
   unsigned getNodePredicate(TreePredicateFn Pred) {
-    unsigned &Entry = NodePredicateMap[Pred.getOrigPatFragRecord()];
+    TreePattern *TP = Pred.getOrigPatFragRecord();
+    unsigned &Entry = NodePredicateMap[TP];
     if (Entry == 0) {
-      NodePredicates.push_back(Pred);
-      Entry = NodePredicates.size();
+      TinyPtrVector<TreePattern *> &SameCodePreds =
+          NodePredicatesByCodeToRun[Pred.getCodeToRunOnSDNode()];
+      if (SameCodePreds.empty()) {
+        // We've never seen a predicate with the same code: allocate an entry.
+        NodePredicates.push_back(Pred);
+        Entry = NodePredicates.size();
+      } else {
+        // We did see an identical predicate: re-use it.
+        Entry = NodePredicateMap[SameCodePreds.front()];
+        assert(Entry != 0);
+      }
+      // In both cases, we've never seen this particular predicate before, so
+      // mark it in the list of predicates sharing the same code.
+      SameCodePreds.push_back(TP);
     }
     return Entry-1;
   }
@@ -635,7 +653,10 @@ void MatcherTableEmitter::EmitPredicateFunctions(formatted_raw_ostream &OS) {
       TreePredicateFn PredFn = NodePredicates[i];
       
       assert(!PredFn.isAlwaysTrue() && "No code in this predicate");
-      OS << "  case " << i << ": { // " << NodePredicates[i].getFnName() <<'\n';
+      OS << "  case " << i << ": { \n";
+      for (auto *SimilarPred :
+           NodePredicatesByCodeToRun[PredFn.getCodeToRunOnSDNode()])
+        OS << "    // " << TreePredicateFn(SimilarPred).getFnName() <<'\n';
       
       OS << PredFn.getCodeToRunOnSDNode() << "\n  }\n";
     }
-- 
2.34.1