[PATCH] D60765: [ELF] Place SectionPiece::{Live,Hash} bit fields together

[Fangrui Song via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rLLD358645: [ELF] Place SectionPiece::{Live,Hash} bit fields together (authored by MaskRay, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D60765?vs=195340&id=195682#toc

Repository:
  rLLD LLVM Linker

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D60765/new/

https://reviews.llvm.org/D60765

Files:
  ELF/InputSection.h
  ELF/SyntheticSections.cpp
  ELF/SyntheticSections.h


Index: ELF/InputSection.h
===================================================================
--- ELF/InputSection.h
+++ ELF/InputSection.h
@@ -227,13 +227,12 @@
 // be found by looking at the next one).
 struct SectionPiece {
   SectionPiece(size_t Off, uint32_t Hash, bool Live)
-      : InputOff(Off), Hash(Hash), OutputOff(0),
-        Live(Live || !Config->GcSections) {}
+      : InputOff(Off), Live(Live || !Config->GcSections), Hash(Hash >> 1) {}
 
   uint32_t InputOff;
-  uint32_t Hash;
-  int64_t OutputOff : 63;
-  uint64_t Live : 1;
+  uint32_t Live : 1;
+  uint32_t Hash : 31;
+  uint64_t OutputOff = 0;
 };
 
 static_assert(sizeof(SectionPiece) == 16, "SectionPiece is too big");
Index: ELF/SyntheticSections.h
===================================================================
--- ELF/SyntheticSections.h
+++ ELF/SyntheticSections.h
@@ -859,7 +859,8 @@
   // If we use lower bits, it significantly increases the probability of
   // hash collisons.
   size_t getShardId(uint32_t Hash) {
-    return Hash >> (32 - llvm::countTrailingZeros(NumShards));
+    assert((Hash >> 31) == 0);
+    return Hash >> (31 - llvm::countTrailingZeros(NumShards));
   }
 
   // Section size
Index: ELF/SyntheticSections.cpp
===================================================================
--- ELF/SyntheticSections.cpp
+++ ELF/SyntheticSections.cpp
@@ -2876,8 +2876,10 @@
   parallelForEachN(0, Concurrency, [&](size_t ThreadId) {
     for (MergeInputSection *Sec : Sections) {
       for (size_t I = 0, E = Sec->Pieces.size(); I != E; ++I) {
+        if (!Sec->Pieces[I].Live)
+          continue;
         size_t ShardId = getShardId(Sec->Pieces[I].Hash);
-        if ((ShardId & (Concurrency - 1)) == ThreadId && Sec->Pieces[I].Live)
+        if ((ShardId & (Concurrency - 1)) == ThreadId)
           Sec->Pieces[I].OutputOff = Shards[ShardId].add(Sec->getData(I));
       }
     }


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