AMDGPU: Avoid emitting "true" predicates

Empty condition strings are considerde always true. This removes a lot
of clutter from the generated matcher tables.

This shrinks the source size of AMDGPUGenDAGISel.inc from 7.3M to
6.1M.

llvm-svn: 367326

5 files changed, 16 insertions, 5 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUInstructions.td b/llvm/lib/Target/AMDGPU/AMDGPUInstructions.td
index 6efd578807e..885bfc7824c 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUInstructions.td
+++ b/llvm/lib/Target/AMDGPU/AMDGPUInstructions.td
@@ -75,7 +75,7 @@ class ILFormat<dag outs, dag ins, string asmstr, list<dag> pattern>
      let isCodeGenOnly = 1;
 }
 
-def TruePredicate : Predicate<"true">;
+def TruePredicate : Predicate<"">;
 
 class PredicateControl {
   Predicate SubtargetPredicate = TruePredicate;
diff --git a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
index c8f710d66a0..75890d2718d 100644
--- a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
+++ b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
@@ -1373,8 +1373,10 @@ getPatternComplexity(const CodeGenDAGPatterns &CGP) const {
 ///
 std::string PatternToMatch::getPredicateCheck() const {
   SmallVector<const Predicate*,4> PredList;
-  for (const Predicate &P : Predicates)
-    PredList.push_back(&P);
+  for (const Predicate &P : Predicates) {
+    if (!P.getCondString().empty())
+      PredList.push_back(&P);
+  }
   llvm::sort(PredList, deref<llvm::less>());
 
   std::string Check;
diff --git a/llvm/utils/TableGen/CodeGenDAGPatterns.h b/llvm/utils/TableGen/CodeGenDAGPatterns.h
index 2b49a64c3f1..d41de68f02f 100644
--- a/llvm/utils/TableGen/CodeGenDAGPatterns.h
+++ b/llvm/utils/TableGen/CodeGenDAGPatterns.h
@@ -1075,8 +1075,11 @@ public:
     std::string C = IsHwMode
         ? std::string("MF->getSubtarget().checkFeatures(\"" + Features + "\")")
         : std::string(Def->getValueAsString("CondString"));
+    if (C.empty())
+      return "";
     return IfCond ? C : "!("+C+')';
   }
+
   bool operator==(const Predicate &P) const {
     return IfCond == P.IfCond && IsHwMode == P.IsHwMode && Def == P.Def;
   }
diff --git a/llvm/utils/TableGen/GlobalISelEmitter.cpp b/llvm/utils/TableGen/GlobalISelEmitter.cpp
index f1c02134198..65c96069808 100644
--- a/llvm/utils/TableGen/GlobalISelEmitter.cpp
+++ b/llvm/utils/TableGen/GlobalISelEmitter.cpp
@@ -3212,7 +3212,7 @@ Error
 GlobalISelEmitter::importRulePredicates(RuleMatcher &M,
                                         ArrayRef<Predicate> Predicates) {
   for (const Predicate &P : Predicates) {
-    if (!P.Def)
+    if (!P.Def || P.getCondString().empty())
       continue;
     declareSubtargetFeature(P.Def);
     M.addRequiredFeature(P.Def);
diff --git a/llvm/utils/TableGen/SubtargetFeatureInfo.cpp b/llvm/utils/TableGen/SubtargetFeatureInfo.cpp
index edf0b4a01c6..33475f2d111 100644
--- a/llvm/utils/TableGen/SubtargetFeatureInfo.cpp
+++ b/llvm/utils/TableGen/SubtargetFeatureInfo.cpp
@@ -38,6 +38,10 @@ SubtargetFeatureInfo::getAll(const RecordKeeper &Records) {
     if (Pred->getName().empty())
       PrintFatalError(Pred->getLoc(), "Predicate has no name!");
 
+    // Ignore always true predicates.
+    if (Pred->getValueAsString("CondString").empty())
+      continue;
+
     SubtargetFeatures.emplace_back(
         Pred, SubtargetFeatureInfo(Pred, SubtargetFeatures.size()));
   }
@@ -95,8 +99,10 @@ void SubtargetFeatureInfo::emitComputeAvailableFeatures(
   OS << "  PredicateBitset Features;\n";
   for (const auto &SF : SubtargetFeatures) {
     const SubtargetFeatureInfo &SFI = SF.second;
+    StringRef CondStr = SFI.TheDef->getValueAsString("CondString");
+    assert(!CondStr.empty() && "true predicate should have been filtered");
 
-    OS << "  if (" << SFI.TheDef->getValueAsString("CondString") << ")\n";
+    OS << "  if (" << CondStr << ")\n";
     OS << "    Features[" << SFI.getEnumBitName() << "] = 1;\n";
   }
   OS << "  return Features;\n";