[llvm] cbaae61 - [DebugInstrRef] Use DenseMap for ValueToLoc (NFC)

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-01-18T17:02:14+01:00
New Revision: cbaae614224211d01b385227e7efb447c87fc3ce

URL: https://github.com/llvm/llvm-project/commit/cbaae614224211d01b385227e7efb447c87fc3ce
DIFF: https://github.com/llvm/llvm-project/commit/cbaae614224211d01b385227e7efb447c87fc3ce.diff

LOG: [DebugInstrRef] Use DenseMap for ValueToLoc (NFC)

Just replacing std::map with DenseMap here is a major regression
-- because this code used an identity hash for ValueIDNum.
Because ValueIDNum is composed of multiple components, it is
important that we use a reasonably good hash function here, so
switch it to hash_value. DenseMapInfo::getHashValue<uint64_t>
would not be sufficient.

This gives a -0.8% geomean improvement on CTMark ReleaseLTO-g.

Added: 
    

Modified: 
    llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
    llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
index ad8472c436ab0..5d72428f1aecf 100644
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
@@ -272,7 +272,7 @@ class TransferTracker {
     };
 
     // Map of the preferred location for each value.
-    std::map<ValueIDNum, LocIdx> ValueToLoc;
+    DenseMap<ValueIDNum, LocIdx> ValueToLoc;
     ActiveMLocs.reserve(VLocs.size());
     ActiveVLocs.reserve(VLocs.size());
 

diff  --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h
index 6423ff74b563a..9e9c0ce394fd5 100644
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h
@@ -1082,7 +1082,9 @@ template <> struct DenseMapInfo<ValueIDNum> {
     return ValueIDNum::TombstoneValue;
   }
 
-  static unsigned getHashValue(const ValueIDNum &Val) { return Val.asU64(); }
+  static unsigned getHashValue(const ValueIDNum &Val) {
+    return hash_value(Val.asU64());
+  }
 
   static bool isEqual(const ValueIDNum &A, const ValueIDNum &B) {
     return A == B;