[llvm] fae221e - [gcov] Simplify/speed up CFG hash calculation

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2020-07-26T21:15:33-07:00
New Revision: fae221e7ad5a94ed7697c13d169db18d253f5f15

URL: https://github.com/llvm/llvm-project/commit/fae221e7ad5a94ed7697c13d169db18d253f5f15
DIFF: https://github.com/llvm/llvm-project/commit/fae221e7ad5a94ed7697c13d169db18d253f5f15.diff

LOG: [gcov] Simplify/speed up CFG hash calculation

Added: 
    

Modified: 
    llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp b/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
index cd2ea8d5e4ed..53a89f7348de 100644
--- a/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
@@ -32,6 +32,7 @@
 #include "llvm/IR/Module.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
+#include "llvm/Support/CRC.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/FileSystem.h"
@@ -300,15 +301,16 @@ namespace {
       assert(OutEdges.empty());
     }
 
+    uint32_t Number;
+    SmallVector<GCOVBlock *, 4> OutEdges;
+
    private:
     friend class GCOVFunction;
 
     GCOVBlock(GCOVProfiler *P, uint32_t Number)
         : GCOVRecord(P), Number(Number) {}
 
-    uint32_t Number;
     StringMap<GCOVLines> LinesByFile;
-    SmallVector<GCOVBlock *, 4> OutEdges;
   };
 
   // A function has a unique identifier, a checksum (we leave as zero) and a
@@ -347,18 +349,6 @@ namespace {
       return ReturnBlock;
     }
 
-    std::string getEdgeDestinations() {
-      std::string EdgeDestinations;
-      raw_string_ostream EDOS(EdgeDestinations);
-      Function *F = Blocks.begin()->first->getParent();
-      for (BasicBlock &I : *F) {
-        GCOVBlock &Block = getBlock(&I);
-        for (int i = 0, e = Block.OutEdges.size(); i != e; ++i)
-          EDOS << Block.OutEdges[i]->Number;
-      }
-      return EdgeDestinations;
-    }
-
     uint32_t getFuncChecksum() const {
       return FuncChecksum;
     }
@@ -729,7 +719,7 @@ void GCOVProfiler::emitProfileNotes() {
       continue;
     }
 
-    std::string EdgeDestinations;
+    std::vector<uint8_t> EdgeDestinations;
 
     Endian = M->getDataLayout().isLittleEndian() ? support::endianness::little
                                                  : support::endianness::big;
@@ -774,6 +764,11 @@ void GCOVProfiler::emitProfileNotes() {
         } else if (isa<ReturnInst>(TI)) {
           Block.addEdge(Func.getReturnBlock());
         }
+        for (GCOVBlock *Succ : Block.OutEdges) {
+          uint32_t Idx = Succ->Number;
+          do EdgeDestinations.push_back(Idx & 255);
+          while ((Idx >>= 8) > 0);
+        }
 
         for (auto &I : BB) {
           // Debug intrinsic locations correspond to the location of the
@@ -798,12 +793,13 @@ void GCOVProfiler::emitProfileNotes() {
         }
         Line = 0;
       }
-      EdgeDestinations += Func.getEdgeDestinations();
     }
 
     char Tmp[4];
+    JamCRC JC;
+    JC.update(EdgeDestinations);
     os = &out;
-    auto Stamp = static_cast<uint32_t>(hash_value(EdgeDestinations));
+    uint32_t Stamp = JC.getCRC();
     FileChecksums.push_back(Stamp);
     if (Endian == support::endianness::big) {
       out.write("gcno", 4);