[PATCH] D121051: [lld-macho][nfc] Track # of ICF calls to `equals*` methods

[Jez Ng via Phabricator via llvm-commits]

int3 created this revision.
int3 added a reviewer: lld-macho.
Herald added projects: lld-macho, All.
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This is debug code that is disabled by default. It'll provide a easy way
to figure out the impact (if any) of tweaking ICF's hashing algorithm
(since a poor quality hash will result in many more `equals*` calls).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D121051

Files:
  lld/MachO/ICF.cpp


Index: lld/MachO/ICF.cpp
===================================================================
--- lld/MachO/ICF.cpp
+++ lld/MachO/ICF.cpp
@@ -23,6 +23,8 @@
 using namespace lld;
 using namespace lld::macho;
 
+constexpr bool verboseDiagnostics = false;
+
 class ICF {
 public:
   ICF(std::vector<ConcatInputSection *> &inputs);
@@ -47,6 +49,8 @@
 
   unsigned icfPass = 0;
   std::atomic<bool> icfRepeat{false};
+  std::atomic<uint64_t> equalsConstantCount{0};
+  std::atomic<uint64_t> equalsVariableCount{0};
 };
 
 ICF::ICF(std::vector<ConcatInputSection *> &inputs) {
@@ -87,6 +91,8 @@
 // except references to other ConcatInputSections.
 bool ICF::equalsConstant(const ConcatInputSection *ia,
                          const ConcatInputSection *ib) {
+  if (verboseDiagnostics)
+    ++equalsConstantCount;
   // We can only fold within the same OutputSection.
   if (ia->parent != ib->parent)
     return false;
@@ -157,6 +163,8 @@
 // handled by equalsConstant().
 bool ICF::equalsVariable(const ConcatInputSection *ia,
                          const ConcatInputSection *ib) {
+  if (verboseDiagnostics)
+    ++equalsVariableCount;
   assert(ia->relocs.size() == ib->relocs.size());
   auto f = [this](const Reloc &ra, const Reloc &rb) {
     // We already filtered out mismatching values/addends in equalsConstant.
@@ -305,6 +313,10 @@
     });
   } while (icfRepeat);
   log("ICF needed " + Twine(icfPass) + " iterations");
+  if (verboseDiagnostics) {
+    log("equalsConstant() called " + Twine(equalsConstantCount) + " times");
+    log("equalsVariable() called " + Twine(equalsVariableCount) + " times");
+  }
 
   // Fold sections within equivalence classes
   forEachClass([&](size_t begin, size_t end) {


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