[PATCH] D135977: [LV] Simplify register usage code and avoid double map lookups.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: fhahn, reames.
Herald added subscribers: StephenFan, hiraditya.
Herald added a project: All.
craig.topper requested review of this revision.
Herald added a subscriber: pcwang-thead.
Herald added a project: LLVM.

Instead of checking whether a map entry exists to decide if we should
initialize it or add to it, we can rely on the map entry being constructed
and initialized to 0 before the addition happens.

For the std::max case, I've made a reference to the map entry to
avoid looking it up twice.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D135977

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp


Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -6026,10 +6026,9 @@
       if (VFs[j].isScalar()) {
         for (auto *Inst : OpenIntervals) {
           unsigned ClassID = TTI.getRegisterClassForType(false, Inst->getType());
-          if (RegUsage.find(ClassID) == RegUsage.end())
-            RegUsage[ClassID] = 1;
-          else
-            RegUsage[ClassID] += 1;
+          // If RegUsage[ClassID] doesn't exist, it will be default
+          // constructed as 0 before the addition
+          RegUsage[ClassID] += 1;
         }
       } else {
         collectUniformsAndScalars(VFs[j]);
@@ -6039,25 +6038,21 @@
             continue;
           if (isScalarAfterVectorization(Inst, VFs[j])) {
             unsigned ClassID = TTI.getRegisterClassForType(false, Inst->getType());
-            if (RegUsage.find(ClassID) == RegUsage.end())
-              RegUsage[ClassID] = 1;
-            else
-              RegUsage[ClassID] += 1;
+            // If RegUsage[ClassID] doesn't exist, it will be default
+            // constructed as 0 before the addition
+            RegUsage[ClassID] += 1;
           } else {
             unsigned ClassID = TTI.getRegisterClassForType(true, Inst->getType());
-            if (RegUsage.find(ClassID) == RegUsage.end())
-              RegUsage[ClassID] = GetRegUsage(Inst->getType(), VFs[j]);
-            else
-              RegUsage[ClassID] += GetRegUsage(Inst->getType(), VFs[j]);
+            // If RegUsage[ClassID] doesn't exist, it will be default
+            // constructed as 0 before the addition
+            RegUsage[ClassID] += GetRegUsage(Inst->getType(), VFs[j]);
           }
         }
       }
 
       for (auto& pair : RegUsage) {
-        if (MaxUsages[j].find(pair.first) != MaxUsages[j].end())
-          MaxUsages[j][pair.first] = std::max(MaxUsages[j][pair.first], pair.second);
-        else
-          MaxUsages[j][pair.first] = pair.second;
+        auto &Entry = MaxUsages[j][pair.first];
+        Entry = std::max(Entry, pair.second);
       }
     }
 


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