[llvm] 72e1441 - [TableGen] Slightly improve the efficiency of InfoByHwMode::get.

[Craig Topper via llvm-commits]

Author: Craig Topper
Date: 2023-04-08T18:54:56-07:00
New Revision: 72e1441c7a3067a303bd0909f9928af8d5bf1769

URL: https://github.com/llvm/llvm-project/commit/72e1441c7a3067a303bd0909f9928af8d5bf1769
DIFF: https://github.com/llvm/llvm-project/commit/72e1441c7a3067a303bd0909f9928af8d5bf1769.diff

LOG: [TableGen] Slightly improve the efficiency of InfoByHwMode::get.

This avoids some double map lookups. Also use Map.begin() to find
the default mode instead of going through find.

Added: 
    

Modified: 
    llvm/utils/TableGen/InfoByHwMode.cpp
    llvm/utils/TableGen/InfoByHwMode.h

Removed: 
    


################################################################################
diff  --git a/llvm/utils/TableGen/InfoByHwMode.cpp b/llvm/utils/TableGen/InfoByHwMode.cpp
index 5140c5a0d20f..4e9136e936af 100644
--- a/llvm/utils/TableGen/InfoByHwMode.cpp
+++ b/llvm/utils/TableGen/InfoByHwMode.cpp
@@ -65,8 +65,8 @@ MVT &ValueTypeByHwMode::getOrCreateTypeForMode(unsigned Mode, MVT Type) {
     return F->second;
   // If Mode is not in the map, look up the default mode. If it exists,
   // make a copy of it for Mode and return it.
-  auto D = Map.find(DefaultMode);
-  if (D != Map.end())
+  auto D = Map.begin();
+  if (D != Map.end() && D->first == DefaultMode)
     return Map.insert(std::make_pair(Mode, D->second)).first->second;
   // If default mode is not present either, use provided Type.
   return Map.insert(std::make_pair(Mode, Type)).first->second;

diff  --git a/llvm/utils/TableGen/InfoByHwMode.h b/llvm/utils/TableGen/InfoByHwMode.h
index cb20795c03a6..dc760292578f 100644
--- a/llvm/utils/TableGen/InfoByHwMode.h
+++ b/llvm/utils/TableGen/InfoByHwMode.h
@@ -110,20 +110,27 @@ struct InfoByHwMode {
   LLVM_ATTRIBUTE_ALWAYS_INLINE
   bool hasMode(unsigned M) const { return Map.find(M) != Map.end(); }
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  bool hasDefault() const { return hasMode(DefaultMode); }
+  bool hasDefault() const {
+    return !Map.empty() && Map.begin()->first == DefaultMode;
+  }
 
   InfoT &get(unsigned Mode) {
-    if (!hasMode(Mode)) {
-      assert(hasMode(DefaultMode));
-      Map.insert({Mode, Map.at(DefaultMode)});
-    }
-    return Map.at(Mode);
+    auto F = Map.find(Mode);
+    if (F != Map.end())
+      return F->second;
+
+    // Copy and insert the default mode which should be first.
+    assert(hasDefault());
+    auto P = Map.insert({Mode, Map.begin()->second});
+    return P.first->second;
   }
   const InfoT &get(unsigned Mode) const {
     auto F = Map.find(Mode);
-    if (Mode != DefaultMode && F == Map.end())
-      F = Map.find(DefaultMode);
-    assert(F != Map.end());
+    if (F != Map.end())
+      return F->second;
+    // Get the default mode which should be first.
+    F = Map.begin();
+    assert(F != Map.end() && F->first == DefaultMode);
     return F->second;
   }